linux.kernel - 26 new messages in 19 topics - digest
linux.kernel
http://groups.google.com/group/linux.kernel?hl=en
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Today's topics:
* spi: omap2-mcspi: raw read and write endian fix - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/61c361b93c246cfd?hl=en
* A minor amd64_edac fix for 3.13 - 2 messages, 2 authors
http://groups.google.com/group/linux.kernel/t/966a3374765f3154?hl=en
* staging/lustre/llite: Access to released file trigs a restore - 2 messages,
1 author
http://groups.google.com/group/linux.kernel/t/b9af2ffb60231fd2?hl=en
* [PATCH] openrisc: Add DTS and defconfig for DE0-Nano - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/c263cbd25f63fd99?hl=en
* [RFCv2] ASoC: Add support for BCM2835 - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/ddbe79731f4ae07e?hl=en
* : REGRESSION: "*ERROR* Timed out waiting for forcewake old ack to clear" - 2
messages, 2 authors
http://groups.google.com/group/linux.kernel/t/463ef67d8af2a4ae?hl=en
* dmaengine: Add support for BCM2835 - 3 messages, 2 authors
http://groups.google.com/group/linux.kernel/t/b23d68fe8dd6e857?hl=en
* printk: Defer printing to irq work when we printed too much - 1 messages, 1
author
http://groups.google.com/group/linux.kernel/t/7bc00cc28be7d4b5?hl=en
* perf tip: fails to convert comm - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/5eff5c722c706d30?hl=en
* pwm: Changes for v3.13-rc1 - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/d8b378e1210d0776?hl=en
* documentation: Update circular buffer for load-acquire/store-release - 1
messages, 1 author
http://groups.google.com/group/linux.kernel/t/9d3de39c23ef46a9?hl=en
* of: make of_get_phy_mode parse 'phy-connection-type' - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/6029dafbccead828?hl=en
* OF: Introduce utility helper functions - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/0531e1da074770e6?hl=en
* Documentation: gpiolib: document new interface - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/33a7b12a90958969?hl=en
* gpiolib: fix find_chip_by_name() - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/e5465eaabcc515a0?hl=en
* gpiolib: use dedicated flags for GPIO properties - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/076bd57cb3ab2c53?hl=en
* Provide cpupower-idle-set(1) manpage and a minor fix - 3 messages, 1 author
http://groups.google.com/group/linux.kernel/t/d2f0e9371e3a80e3?hl=en
* clocksource: orion: Switch to sched_clock_register() - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/730aeb5245768714?hl=en
* cpufreq: cpufreq-cpu0: Use a sane boot frequency when booting with a
mismatched bootloader configuration - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/689a4c224e999070?hl=en
==============================================================================
TOPIC: spi: omap2-mcspi: raw read and write endian fix
http://groups.google.com/group/linux.kernel/t/61c361b93c246cfd?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 2:20 am
From: Mark Brown
On Sat, Nov 16, 2013 at 02:01:16AM +0200, Taras Kondratiuk wrote:
> From: Victor Kamensky <victor.kamensky@linaro.org>
>
> All OMAP IP blocks expect LE data, but CPU may operate in BE mode.
> Need to use endian neutral functions to read/write h/w registers.
> I.e instead of __raw_read[lw] and __raw_write[lw] functions code
> need to use read[lw]_relaxed and write[lw]_relaxed functions.
> If the first simply reads/writes register, the second will byteswap
> it if host operates in BE mode.
Applied, thanks.
==============================================================================
TOPIC: A minor amd64_edac fix for 3.13
http://groups.google.com/group/linux.kernel/t/966a3374765f3154?hl=en
==============================================================================
== 1 of 2 ==
Date: Sat, Nov 16 2013 2:40 am
From: Borislav Petkov
And just to test whether you're getting emails from me, I'll send this
one again from my other mail address to try to maximize the probability
of some version actually reaching you :-)
On Fri, Nov 15, 2013 at 06:02:59PM -0800, Linus Torvalds wrote:
> [ This was in my spam collection. I don't quite know why, but it might
> signify problems with your email setup. Quite often, when gmail is
> unhappy about kernel developer emails, it's been because their email
> provider ends up doing something odd.
>
> But the headers actually have "spf=pass" and "dkim=pass", so it's
> nothing obvious. ]
Hmm, strange. Does this mean, you don't get other emails from my email
address or only this pull request? Say, do you have this one, for
example:
http://marc.info/?l=linux-kernel&m=138442829620489&w=2
where I ask you whether you're fine with Mauro and me playing interim
EDAC maintainers?
> That said, I don't much like the patch either. The "fixed' version
> looks worse than the original. If it's an unsigned type, no extra code
> will be generated,
Yes, correct, in both cases I have here:
.L779:
.loc 1 1579 0
cmpb $4, %r10b #, alias_channel
ja .L859 #,
.L847:
> and if it's a signed type, it's correct. In either way, the code looks
> good, and the range test means that people reading it don't even need
> to worry about whether the type is signed or not.
>
> If this patch was written because of some f*cking broken compiler
> warning, then just tell the compiler to shut the hell up about it.
> This is a clear example of where compiler warnings are actually making
> things worse.
Yeah, no, the compiler's fine here. Dave raised the issue about not
testing unsigned's for < 0:
http://www.spinics.net/lists/kernel/msg1597525.html
And I took it because it is less code in the .c source file to look at.
But I certainly don't care all that much whether the < 0 test is there
or not as long as the produced code is identical so...
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
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== 2 of 2 ==
Date: Sat, Nov 16 2013 3:20 am
From: Borislav Petkov
On Sat, Nov 16, 2013 at 02:50:49AM -0800, Linus Torvalds wrote:
> As far as I can tell, only that one email had gotten caught by the
> spam filter. So it may be something in the body of the email itself,
> although I don't really see what that could be either..
Right.
> It happens occasionally, although it doors seem to happen much more to
> certain particular people than to others.
AFAIR, it had happened once before with a pull request a couple of
kernel releases back. Oh well, I will start sending the pull requests
from suse.de as their range is statically allocated and this should take
care of the dynamic IP range issues.
> The most common reason seems to be that your email provide is
> associated with spam, sometimes just because of a shared ISP.
Sure, it is one: https://www.hetzner.de/
> It is hard to tell with gmail, since it probably uses heuristics very
> much like spamassassin, but doesn't make the internal scores available
> (to avoid gaming them, I'm sure). So there are likely multiple small
> triggers that combine, rather than one single reason. With "possibly
> bad ISP" probably just being one of them..
Right, I'm adding Frank who takes care of it, just so he's aware.
Thanks.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
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==============================================================================
TOPIC: staging/lustre/llite: Access to released file trigs a restore
http://groups.google.com/group/linux.kernel/t/b9af2ffb60231fd2?hl=en
==============================================================================
== 1 of 2 ==
Date: Sat, Nov 16 2013 2:40 am
From: "Dilger, Andreas"
On 2013/11/14 9:09 PM, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
wrote:
>On Fri, Nov 15, 2013 at 12:13:06AM +0800, Peng Tao wrote:
>> From: JC Lafoucriere <jacques-charles.lafoucriere@cea.fr>
>>
>> When a client accesses data in a released file,
>> or truncate it, client must trig a restore request.
>> During this restore, the client must not glimpse and
>> must use size from MDT. To bring the "restore is running"
>> information on the client we add a new t_state bit field
>> to mdt_info which will be used to carry transient file state.
>> To memorise this information in the inode we add a new flag
>> LLIF_FILE_RESTORING.
>
>This patch also does other things not mentioned here (coding style
>cleanups), which isn't allowed in a single patch (only do one thing per
>patch, and never not document what you are doing...)
>
>It also adds checkpatch warnings, which I will not accept in patches at
>all here. People are spending a lot of time cleaning up the coding
>style issues, please NEVER add new ones, that just causes more work to
>be needed to be done, and for people to have to go back and reclean
>files they have already cleaned up.
I'm fine to clean up the coding style issues in these patches.
>So, sorry, I have to stop here at this series. I've applied the first 3
>to the opw-next branch of staging.git so they can live somewhere until
>3.13-rc1 is out.
>
>I know you spent a lot of time making these 120 patches to send me, but
>that too is crazy. You shouldn't wait that long to get feedback and
>send patches to me at all. Please send them in smaller series, with
>less time between patch submissions.
The reason that there are so many patches in a burst is that we are also
developing new features and fixing bugs in parallel with the kernel, but
they also need to be tested a lot before they are released. It's not any
different from kernel patches testing on -next or -mm for a few months
before they are pushed to the mainline kernel in a batch.
The out-of-tree development can't really stop for a year while the kernel
client code is cleaned up. If the feature patches don't land into the
kernel client for a year (or however long it takes to do all the cleanup),
then it will become outdated and the whole reason for adding the client
into the kernel is lost.
>> There are many users of the external tree so we cannot just abandon
>> it, especially that the upstream client is not shipped in any
>> distribution yet. Thanks for your understanding.
>
>What is keeping people using that tree? Support for older/distro
>kernels?
>
Support for distro kernels is a big part of it. Most HPC sites use vendor
kernels of various vintages, and we need to keep the code working for those
sites. We also need to continue developing features needed by ever-larger
clusters, fixing bugs, etc. Eventually, when Lustre is in the kernel
proper,
it will also be available in future distro kernels and we can eventually
stop supporting the out-of-tree code. I expect that to be 3+ years away.
>Is it the fact that the server code isn't in the kernel?
Not really. Lustre servers are on separate servers with vendor kernels
(ancient by your standards), and there isn't really any demand for
using newer kernels on those nodes. Most importantly, the out-of-tree
branch is where all of the new feature development is being done. That
also means if feature patches don't land into the kernel it just makes
the kernel version less attractive for users.
> Should that be added now too so that we can get a proper view of what
> can and can not be changed? Some of your patches are showing that things
> are shared by the two chunks of code, so does that mean if I delete
>things in the client code that don't look to be used by anything, you
> will have problems because the server now breaks?
Adding the server code to staging would mean another 150kLOC in staging.
We also haven't cleaned that code up even nearly as much as the client
code, so it isn't really even ready to go into staging either. I don't
think you or anyone else would be happy to see that code yet, so I don't
think there is a real advantage to do so.
Deleting unused code in the kernel client isn't fatal, since we'll
still have the out-of-tree version, but we're trying to keep the code in
sync as much as possible so that it is easier to port patches in both
directions. If code is deleted it means more that needs to be added
back later when the server eventually does get merged, and more effort
to resolve patch conflicts.
>I think it's time to just merge the server and deal with the whole thing
>all at once, otherwise this dependancy on your external tree, and
>external code to the kernel, is going to doom the ability to ever get
>this code cleaned up and merged properly.
Regardless of whether the Lustre server is added to the kernel or not,
we need to maintain support for the older kernels, so there will need
to be an external tree for years to come until Lustre is available in
vendor kernels. I'm sure we can't merge in the kernel-version-portable
code into the kernel, so there isn't really any choice but to try and
keep both trees in sync.
Cheers, Andreas
--
Andreas Dilger
Lustre Software Architect
Intel High Performance Data Division
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== 2 of 2 ==
Date: Sat, Nov 16 2013 3:30 am
From: "Dilger, Andreas"
On 2013/11/14 9:13 PM, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
wrote:
>On Fri, Nov 15, 2013 at 12:13:07AM +0800, Peng Tao wrote:
>> From: "John L. Hammond" <john.hammond@intel.com>
>>
>> Add a const void *h_owner member to struct portals_handle. Add a const
>> void *owner parameter to class_handle2object() which must be matched
>> by the h_owner member of the handle in addition to the cookie.
>
>Ick ick ick.
>
>NEVER use a void pointer if you can help it, and for a "handle", never.
>This isn't other operating systems, sorry. We know what types our
>pointers to structures are, use them, so that the compiler can catch our
>problems, and don't try to cheat by using void *.
The portals_handle is used as a generic type for objects referenced over
the network, like a file handle. The "owner" parameter is just used as
an extra check that the cookie passed from the client is actually a
valid value for the code in which it is being used (e.g. metadata or
data object). It isn't actually dereferenced by anything, it is just
like a magic value.
>> Adjust
>> the callers of class_handle2object() accordingly, using NULL as the
>> argument to the owner parameter, except in the case of
>> mdt_handle2mfd() where we add an explicit mdt_export_data parameter
>> which we use as the owner when searching for a MFD. When allocating a
>> new MFD, pass a pointer to the mdt_export_data into mdt_mfd_new() and
>> store it in h_owner. This allows the MDT to validate that the client
>> has not sent the wrong open handle cookie, or sent the right cookie to
>> the wrong MDT.
>
>This changelog entry doesn't even match up with the code below. ALl
>callers of class_handle2object are passing NULL here, which makes this
>patch pretty pointless, right?
As Tao wrote, this is the patch summary that matches what was committed
in our own tree and in this case mostly describes the changes made on the
server. Keeping the same commits and comments in both trees makes it
easier to keep the code in sync.
>And that's a _very_ generic global symbol name, please don't do that, it
>needs to be "lustre_*" at the front to even expect it to be acceptable.
There's already something else called a "lustre_handle", so what about
obdclass_handle2object(), since this is in the obdclass module?
Cheers, Andreas
--
Andreas Dilger
Lustre Software Architect
Intel High Performance Data Division
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==============================================================================
TOPIC: [PATCH] openrisc: Add DTS and defconfig for DE0-Nano
http://groups.google.com/group/linux.kernel/t/c263cbd25f63fd99?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 3:10 am
From: Olof Kindgren
2013/11/16 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
>
> On Fri, Nov 15, 2013 at 10:50:18AM +0100, Jonas Bonn wrote:
> > >+
> > >+ i2c0: ocores@a0000000 {
> > >+ #address-cells = <1>;
> > >+ #size-cells = <0>;
> > >+ compatible = "opencores,i2c-ocores";
> >
> > Version number needed. OpenCores wanted "projectname-rtlsvn###"
> > where ### is the SVN commit number of the RTL directory in the
> > project's source repository.
> >
>
> That will also require a change to the driver.
>
> Using svn commit ids as version info seems a bit too fine grained to me,
> but if that's what's agreed on, then it should be the commit id from the
> projects official repository at opencores.org I think.
>
> Stefan
> _______________________________________________
> Linux mailing list
> Linux@lists.openrisc.net
> http://lists.openrisc.net/listinfo/linux
I agree. I don't like doing versioning with revision numbers. It's too
closely tied to the currently used VCS. The problem is that no one has
bothered to do proper releases of the cores for the last ten years or
so.
But since we are talking about a relatively small amount of cores
here, I think it could be worth to take a quick glance to see if the
latest SVN version is compatible with the latest tagged release. I
would suspect that is the case for the majority of the cores and the
we can just use the latest tag as version. For the other cores we
could
1. Use latest tag + 1 (a bit ugly if the maintainer wants to do a proper release
2. Take over maintainership/fork and just release what's in the trunk
(taking over maintenance is preferrable here to avoid more repo
confusion)
3. Use SVN revisions
option 2 would be my preferred choice here, given that we get someone
to do the actual work. I could probably help out with a few of the
cores
Jonas, you said that opencores wanted projectname-svnversion. Do you
know where that comes from? My proposal here would conflict with that
//Olof
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==============================================================================
TOPIC: [RFCv2] ASoC: Add support for BCM2835
http://groups.google.com/group/linux.kernel/t/ddbe79731f4ae07e?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 3:20 am
From: Lars-Peter Clausen
On 11/12/2013 07:41 PM, Florian Meier wrote:
> This driver adds support for digital audio (I2S)
> for the BCM2835 SoC that is used by the
> Raspberry Pi. External audio codecs can be
> connected to the Raspberry Pi via P5 header.
>
> It relies on cyclic DMA engine support for BCM2835.
>
> Signed-off-by: Florian Meier <florian.meier@koalo.de>
Looks mostly good in my opinion. A few comments on minor bits and pieces.
> diff --git a/sound/soc/bcm/Kconfig b/sound/soc/bcm/Kconfig
> new file mode 100644
> index 0000000..93619ec
> --- /dev/null
> +++ b/sound/soc/bcm/Kconfig
> @@ -0,0 +1,15 @@
> +config SND_BCM2835_SOC_I2S
> + tristate
> +
> +config SND_BCM2835_SOC
> + tristate "SoC Audio support for the Broadcom BCM2835 I2S module"
> + depends on ARCH_BCM2835
I think there is no compile time dependency on ARCH_BCM2835. Changing this
to 'depends on ARCH_BCM2835 || COMPILE_TEST' allows to archive better build
test coverage for the driver.
> + select SND_SOC_DMAENGINE_PCM
> + select DMADEVICES
> + select DMA_BCM2835
I don't think its a good idea to select DMADEVICES or DMA_BCM2835 here,
since those are user selectable symbols from another subsystem. Either
'depends on DMA_BCM2835' or nothing. Will I think nothing is better since
there is no compile time dependency.
> + select SND_SOC_GENERIC_DMAENGINE_PCM
> + select REGMAP_MMIO
> + help
> + Say Y or M if you want to add support for codecs attached to
> + the BCM2835 I2S interface. You will also need
> + to select the audio interfaces to support below.
[...]
> +static void bcm2835_i2s_clear_fifos(struct bcm2835_i2s_dev *dev,
> + bool tx, bool rx)
> +{
> + int timeout = 1000;
> + uint32_t syncval;
> + uint32_t csreg;
> + uint32_t i2s_active_state;
> + uint32_t clkreg;
> + uint32_t clk_active_state;
> + uint32_t off;
> + uint32_t clr;
> +
> + off = tx ? BCM2835_I2S_TXON : 0;
> + off |= rx ? BCM2835_I2S_RXON : 0;
> +
> + clr = tx ? BCM2835_I2S_TXCLR : 0;
> + clr |= rx ? BCM2835_I2S_RXCLR : 0;
> +
> + /* Backup the current state */
> + regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &csreg);
> + i2s_active_state = csreg & (BCM2835_I2S_RXON | BCM2835_I2S_TXON);
> +
> + regmap_read(dev->clk_regmap, BCM2835_CLK_PCMCTL_REG, &clkreg);
> + clk_active_state = clkreg & BCM2835_CLK_ENAB;
> +
> + /* Start clock if not running */
> + if (!clk_active_state) {
> + regmap_update_bits(dev->clk_regmap, BCM2835_CLK_PCMCTL_REG,
> + BCM2835_CLK_PASSWD_MASK | BCM2835_CLK_ENAB,
> + BCM2835_CLK_PASSWD | BCM2835_CLK_ENAB);
> + }
> +
> + /* Stop I2S module */
> + regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, off, 0);
> +
> + /*
> + * Clear the FIFOs
> + * Requires at least 2 PCM clock cycles to take effect
> + */
> + regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, clr, -1);
I think the -1 can be confusing. Better use either clr or 0xffffffff. Same
applies to a few other places in the driver.
> +
> + /* Wait for 2 PCM clock cycles */
> +
> + /*
> + * Toggle the SYNC flag - after 2 PCM clock cycles it can be read back
> + * FIXME: This does not seem to work for slave mode!
> + */
> + regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &syncval);
> + syncval &= BCM2835_I2S_SYNC;
> +
> + regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
> + BCM2835_I2S_SYNC, ~syncval);
> +
> + /* Wait for the SYNC flag changing it's state */
> + while (timeout > 0) {
> + timeout--;
> +
> + regmap_read(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, &csreg);
> + if ((csreg & BCM2835_I2S_SYNC) != syncval)
> + break;
> + }
> +
> + if (timeout <= 0)
> + dev_err(dev->dev, "I2S SYNC error!\n");
> +
> + /* Stop clock if it was not running before */
> + if (!clk_active_state)
> + bcm2835_i2s_stop_clock(dev);
> +
> + /* Restore I2S state */
> + regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
> + BCM2835_I2S_RXON | BCM2835_I2S_TXON, i2s_active_state);
> +}
> +
[...]
> +static int bcm2835_i2s_dai_probe(struct snd_soc_dai *dai)
> +{
> + struct bcm2835_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
> +
> + dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].addr_width =
> + DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].addr_width =
> + DMA_SLAVE_BUSWIDTH_4_BYTES;
> +
> + /* TODO other burst parameters possible? */
> + dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].maxburst = 2;
> + dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].maxburst = 2;
I'd move the initialization of dma_data to the driver probe() function.
> +
> + dai->playback_dma_data = &dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK];
> + dai->capture_dma_data = &dev->dma_data[SNDRV_PCM_STREAM_CAPTURE];
snd_soc_dai_init_dma_data()
> +
> + return 0;
> +}
> +
[...]
> +
> +static int bcm2835_i2s_probe(struct platform_device *pdev)
> +{
> + struct bcm2835_i2s_dev *dev;
> + int i;
> + int ret;
> + struct regmap *regmap[2];
> + struct resource *mem[2];
> +
> + /* request both ioareas */
> + for (i = 0; i <= 1; i++) {
> + void __iomem *base;
> +
> + mem[i] = platform_get_resource(pdev, IORESOURCE_MEM, i);
> + if (!mem[i]) {
> + dev_err(&pdev->dev, "I2S probe: Memory resource could not be found.\n");
> + return -ENODEV;
> + }
> +
> + base = devm_ioremap_resource(&pdev->dev, mem[i]);
> + if (!base) {
> + dev_err(&pdev->dev, "I2S probe: ioremap failed.\n");
> + return -ENOMEM;
> + }
> +
> + regmap[i] = devm_regmap_init_mmio(&pdev->dev, base,
> + &bcm2835_regmap_config[i]);
> + if (IS_ERR(regmap[i])) {
> + dev_err(&pdev->dev, "I2S probe: regmap init failed\n");
> + return PTR_ERR(regmap[i]);
> + }
> + }
> +
> + dev = devm_kzalloc(&pdev->dev, sizeof(struct bcm2835_i2s_dev),
sizeof(*dev)
> + GFP_KERNEL);
> + if (!dev) {
> + dev_err(&pdev->dev, "I2S probe: kzalloc failed.\n");
> + return -ENOMEM;
> + }
> +
> + dev->i2s_regmap = regmap[0];
> + dev->clk_regmap = regmap[1];
> +
> + /* Set the DMA address */
> + dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].addr =
> + (dma_addr_t)mem[0]->start + BCM2835_I2S_FIFO_A_REG
> + + BCM2835_VCMMU_SHIFT;
> +
> + dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].addr =
> + (dma_addr_t)mem[0]->start + BCM2835_I2S_FIFO_A_REG
> + + BCM2835_VCMMU_SHIFT;
> +
> + /* Store the pdev */
> + dev->dev = &pdev->dev;
> + dev_set_drvdata(&pdev->dev, dev);
> +
> + ret = snd_soc_register_component(&pdev->dev,
> + &bcm2835_i2s_component, &bcm2835_i2s_dai, 1);
> +
> + if (ret) {
> + dev_err(&pdev->dev, "Could not register DAI: %d\n", ret);
> + ret = -ENOMEM;
> + return ret;
> + }
> +
> + ret = bcm2835_pcm_platform_register(&pdev->dev);
> + if (ret) {
> + dev_err(&pdev->dev, "Could not register PCM: %d\n", ret);
> + snd_soc_unregister_component(&pdev->dev);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static const struct of_device_id bcm2835_i2s_of_match[] = {
> + { .compatible = "brcm,bcm2835-i2s", },
Bindings documentation is missing.
> + {},
> +};
[...]
> +
> +int bcm2835_pcm_platform_register(struct device *dev)
> +{
> + return snd_dmaengine_pcm_register(dev, NULL, 0);
Now that these functions are just simple wrappers for
snd_dmaengine_pcm_{register,unregister}() there is really no need to keep
them around. Just remove bcm2835-pcm.h and .c and call them directly from
the i2s driver.
> +}
> +EXPORT_SYMBOL_GPL(bcm2835_pcm_platform_register);
[...]
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==============================================================================
TOPIC: : REGRESSION: "*ERROR* Timed out waiting for forcewake old ack to clear
"
http://groups.google.com/group/linux.kernel/t/463ef67d8af2a4ae?hl=en
==============================================================================
== 1 of 2 ==
Date: Sat, Nov 16 2013 3:30 am
From: Jörg Otte
On startup I get the following error display on the console:
"*ERROR* Timed out waiting for forcewake old ack to clear"
I already reported this error a year ago at the time of v3.7
( see https://lkml.org/lkml/2012/11/27/355)
which was fixed later on.
Now this error is back again. Kernel 3.12.0-09888-gf63c48
Jörg
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== 2 of 2 ==
Date: Sat, Nov 16 2013 4:10 am
From: Daniel Vetter
On Sat, Nov 16, 2013 at 12:28 PM, Jörg Otte <jrg.otte@gmail.com> wrote:
> On startup I get the following error display on the console:
> "*ERROR* Timed out waiting for forcewake old ack to clear"
>
> I already reported this error a year ago at the time of v3.7
> ( see https://lkml.org/lkml/2012/11/27/355)
> which was fixed later on.
>
> Now this error is back again. Kernel 3.12.0-09888-gf63c48
Please boot with drm.debug=0xe, reproduce the issue and then attach
the complete dmesg (including all the boot message, so if it takes a
while to reproduce please grab an boot dmesg, too).
Also adding the right mailing lists, see MAINTAINERS.
Thanks, Daniel
--
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Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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==============================================================================
TOPIC: dmaengine: Add support for BCM2835
http://groups.google.com/group/linux.kernel/t/b23d68fe8dd6e857?hl=en
==============================================================================
== 1 of 3 ==
Date: Sat, Nov 16 2013 3:30 am
From: Mark Brown
On Sat, Nov 16, 2013 at 11:37:54AM +0200, Andy Shevchenko wrote:
> The reason why I was asking about I'm just wondering what we have to do
> with existing drivers. Shall we convert them to be initialized as normal
> platform drivers instead of subsys_initcall?
We should in general be moving in that direction however it does need a
bit of care to make sure that there aren't any dependencies which do
things like discard error codes, fail to check errors or treat errors as
hard failures.
== 2 of 3 ==
Date: Sat, Nov 16 2013 3:50 am
From: Russell King - ARM Linux
On Sat, Nov 16, 2013 at 11:27:54AM +0000, Mark Brown wrote:
> On Sat, Nov 16, 2013 at 11:37:54AM +0200, Andy Shevchenko wrote:
>
> > The reason why I was asking about I'm just wondering what we have to do
> > with existing drivers. Shall we convert them to be initialized as normal
> > platform drivers instead of subsys_initcall?
>
> We should in general be moving in that direction however it does need a
> bit of care to make sure that there aren't any dependencies which do
> things like discard error codes, fail to check errors or treat errors as
> hard failures.
I don't agree: on platforms which have done this, it's very difficult to
tell from reading the kernel message log whether things came up correctly
because there's soo much spew from deferred probing it's virtually
impossible to tell whether component X initialised or whether that error
about resource Y missing was ever resolved.
The only way that can be checked is when things work (or don't) from
userspace.
It's soo bad on some platforms that reading the kernel boot log is a
total waste of time; you don't get any useful information from it.
If we want kernel boot logs to be useful, we really need to shut up *all*
the drivers and subsystems whinging about being deferred probing, and only
have the driver model core reporting this status - maybe only allow
output about why at debug level or similar.
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== 3 of 3 ==
Date: Sat, Nov 16 2013 4:30 am
From: Mark Brown
On Sat, Nov 16, 2013 at 11:41:34AM +0000, Russell King - ARM Linux wrote:
> On Sat, Nov 16, 2013 at 11:27:54AM +0000, Mark Brown wrote:
> > We should in general be moving in that direction however it does need a
> > bit of care to make sure that there aren't any dependencies which do
> > things like discard error codes, fail to check errors or treat errors as
> > hard failures.
> I don't agree: on platforms which have done this, it's very difficult to
> tell from reading the kernel message log whether things came up correctly
> because there's soo much spew from deferred probing it's virtually
> impossible to tell whether component X initialised or whether that error
> about resource Y missing was ever resolved.
I do agree that deferred programming is far too chatty - there's a
usability issue there. This bites me a lot on some of my systems too, I
tend to read my logs with grep a lot which isn't awesome.
> If we want kernel boot logs to be useful, we really need to shut up *all*
> the drivers and subsystems whinging about being deferred probing, and only
> have the driver model core reporting this status - maybe only allow
> output about why at debug level or similar.
Yes, some sort of standardisation of how this stuff gets reported would
give us much better control of these things.
==============================================================================
TOPIC: printk: Defer printing to irq work when we printed too much
http://groups.google.com/group/linux.kernel/t/7bc00cc28be7d4b5?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 3:40 am
From: Pavel Machek
Hi!
> > > > > Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
> > > > > Signed-off-by: Jan Kara <jack@suse.cz>
> > > >
> > > > When a message takes tens of seconds to be printed, it usually means
> > > > we are in trouble somehow :)
> > > > I wonder what printk source can trigger such a high volume.
> > > Machines with tens of processors and thousands of scsi devices. When
> > > device discovery happens on boot, all processors are busily reporting new
> > > scsi devices and one poor looser is bound to do the printing for ever and
> > > ever until the machine dies...
> >
> > Dunno. In these cases, would it make sense to:
> >
> > 1) reduce amount of text printed
> I thought about this as well. But
> a) It doesn't seem practical as you would have to modify lots of drivers
> and keep them rather silent. That seems rather fragile. Plus you will
> not display some potentially useful information.
> b) It doesn't address the real underlying problem that the way printk() is
> currently implemented, there is no bound on the time CPU spends in the
> loop printing from buffer to console. And the fact that this loop
> sometimes happens with interrupts disabled makes the situation even
> worse.
>
> > 2) just print [XXX characters lost] on overruns?
> We don't overrun the printk buffer so no characters are lost. It just
> takes too long to feed the whole printk buffer through serial console...
Yes, I know. No characters are lost, but we spend seconds with
interrupts disabled, breaking the system. (SCSI timeouts? We do
keyboard autorepeat in software these days...)
Would it be better to just drop the characters?
Pavel
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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==============================================================================
TOPIC: perf tip: fails to convert comm
http://groups.google.com/group/linux.kernel/t/5eff5c722c706d30?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:00 am
From: Namhyung Kim
Hi Frederic,
2013-11-16 (토), 02:02 +0100, Frederic Weisbecker:
> On Fri, Nov 15, 2013 at 09:29:51AM -0700, David Ahern wrote:
> > HI Frederic:
> >
> > On 11/13/13, 11:03 AM, Frederic Weisbecker wrote:
> > >
> > >I see. I can reproduce, I'll check and see what happens. It would be nice if
> > >we could have an option to dump internal perf events like comm events as well
> > >in the perf script stream.
> >
> > Any progress on a solution? This is a regression in 3.13.
>
> So the problem is that when a thread overrides its default ":%pid" comm, we forget
> to tag the thread comm as overriden. Hence, this overriden comm is not inherited on
> future forks.
>
> So here is a fix. Tell me if you see more issue, I'll cook a proper changelog and
> resend if everyting looks good.
>
> Thanks.
>
> diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> index cd8e2f5..49eaf1d 100644
> --- a/tools/perf/util/thread.c
> +++ b/tools/perf/util/thread.c
> @@ -70,14 +70,13 @@ int thread__set_comm(struct thread *thread, const char *str, u64 timestamp)
> /* Override latest entry if it had no specific time coverage */
> if (!curr->start) {
> comm__override(curr, str, timestamp);
> - return 0;
> + } else {
> + new = comm__new(str, timestamp);
> + if (!new)
> + return -ENOMEM;
> + list_add(&new->list, &thread->comm_list);
> }
>
> - new = comm__new(str, timestamp);
> - if (!new)
> - return -ENOMEM;
> -
> - list_add(&new->list, &thread->comm_list);
> thread->comm_set = true;
>
> return 0;
Looks good to me.
Thanks for the fix.
Namhyung
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==============================================================================
TOPIC: pwm: Changes for v3.13-rc1
http://groups.google.com/group/linux.kernel/t/d8b378e1210d0776?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:00 am
From: Thierry Reding
Hi Linus,
The following changes since commit 272b98c6455f00884f0350f775c5342358ebb73f:
Linux 3.12-rc1 (2013-09-16 16:17:51 -0400)
are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm.git tags/pwm/for-3.13-rc1
for you to fetch changes up to 1b3f25ce991d528bd0d825b3f14a45904037a382:
Documentation/pwm: Update supported SoC name for pwm-samsung (2013-11-11 10:23:56 +0100)
Thanks,
Thierry
----------------------------------------------------------------
pwm: Changes for v3.13-rc1
Mostly bug fixes and clean up. There is a new driver, which is actually
moving a custom PWM driver from drivers/misc.
The majority of the patches are enhancements to the device tree support
in the pwm-backlight driver. Backlights can now additionally be powered
using a regulator and enabled using a GPIO in addition to just the PWM
input.
----------------------------------------------------------------
Boris BREZILLON (2):
pwm: atmel-tcb: add missing clk source config
pwm: atmel-tcb: fix max time computation for slow clk source
H Hartley Sweeten (1):
pwm: add ep93xx PWM support
Huayi Li (1):
pwm_backlight: avoid short blank screen while doing hibernation
Mike Dunn (1):
pwm-backlight: Allow for non-increasing brightness levels
Sachin Kamat (10):
pwm: imx: Include linux/of.h header
pwm: samsung: Include linux/of.h header
pwm: twl-led: Include linux/of.h header
pwm: twl: Include linux/of.h header
pwm: mxs: Remove redundant of_match_ptr
pwm: lpc32xx: Remove redundant of_match_ptr
pwm: imx: Remove redundant of_match_ptr
Documentation/pwm: Fix trivial typos
pwm: samsung: Fix kernel warning while unexporting a channel
Documentation/pwm: Update supported SoC name for pwm-samsung
Thierry Reding (14):
pwm-backlight: Improve readability
pwm-backlight: Refactor backlight power on/off
pwm-backlight: Track enable state
pwm-backlight: Add optional enable GPIO
ARM: OMAP: Initialize PWM backlight enable_gpio field
ARM: pxa: Initialize PWM backlight enable_gpio field
ARM: SAMSUNG: Initialize PWM backlight enable_gpio field
ARM: shmobile: Initialize PWM backlight enable_gpio field
unicore32: Initialize PWM backlight enable_gpio field
pwm-backlight: Use new enable_gpio field
pwm-backlight: Add power supply support
pwm-backlight: Fix brightness adjustment
pwm-backlight: Remove unused variable
MAINTAINERS: Move PWM subsystem tree to kernel.org
Wolfram Sang (1):
pwm: don't use devm_pinctrl_get_select_default() in probe
.../devicetree/bindings/pwm/pwm-samsung.txt | 2 +-
.../bindings/video/backlight/pwm-backlight.txt | 7 +
Documentation/pwm.txt | 4 +-
MAINTAINERS | 3 +-
arch/arm/mach-omap2/board-zoom-peripherals.c | 1 +
arch/arm/mach-pxa/cm-x300.c | 1 +
arch/arm/mach-pxa/colibri-pxa270-income.c | 1 +
arch/arm/mach-pxa/ezx.c | 1 +
arch/arm/mach-pxa/hx4700.c | 1 +
arch/arm/mach-pxa/lpd270.c | 1 +
arch/arm/mach-pxa/magician.c | 1 +
arch/arm/mach-pxa/mainstone.c | 1 +
arch/arm/mach-pxa/mioa701.c | 1 +
arch/arm/mach-pxa/palm27x.c | 1 +
arch/arm/mach-pxa/palmtc.c | 35 +--
arch/arm/mach-pxa/palmte2.c | 1 +
arch/arm/mach-pxa/pcm990-baseboard.c | 1 +
arch/arm/mach-pxa/raumfeld.c | 1 +
arch/arm/mach-pxa/tavorevb.c | 2 +
arch/arm/mach-pxa/viper.c | 1 +
arch/arm/mach-pxa/z2.c | 2 +
arch/arm/mach-pxa/zylonite.c | 1 +
arch/arm/mach-s3c24xx/mach-h1940.c | 1 +
arch/arm/mach-s3c24xx/mach-rx1950.c | 1 +
arch/arm/mach-s3c64xx/mach-crag6410.c | 1 +
arch/arm/mach-s3c64xx/mach-hmt.c | 1 +
arch/arm/mach-s3c64xx/mach-smartq.c | 1 +
arch/arm/mach-s3c64xx/mach-smdk6410.c | 1 +
arch/arm/mach-s5p64x0/mach-smdk6440.c | 1 +
arch/arm/mach-s5p64x0/mach-smdk6450.c | 1 +
arch/arm/mach-s5pc100/mach-smdkc100.c | 1 +
arch/arm/mach-s5pv210/mach-smdkv210.c | 1 +
arch/arm/mach-shmobile/board-armadillo800eva.c | 1 +
arch/arm/plat-samsung/dev-backlight.c | 5 +
arch/unicore32/kernel/puv3-nb0916.c | 1 +
drivers/misc/Kconfig | 13 -
drivers/misc/Makefile | 1 -
drivers/misc/ep93xx_pwm.c | 286 ---------------------
drivers/pwm/Kconfig | 9 +
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-atmel-tcb.c | 4 +-
drivers/pwm/pwm-ep93xx.c | 230 +++++++++++++++++
drivers/pwm/pwm-imx.c | 3 +-
drivers/pwm/pwm-lpc32xx.c | 2 +-
drivers/pwm/pwm-mxs.c | 2 +-
drivers/pwm/pwm-samsung.c | 3 +-
drivers/pwm/pwm-tiecap.c | 6 -
drivers/pwm/pwm-tiehrpwm.c | 6 -
drivers/pwm/pwm-twl-led.c | 1 +
drivers/pwm/pwm-twl.c | 1 +
drivers/video/backlight/pwm_bl.c | 166 +++++++++---
include/linux/pwm_backlight.h | 5 +
52 files changed, 434 insertions(+), 392 deletions(-)
delete mode 100644 drivers/misc/ep93xx_pwm.c
create mode 100644 drivers/pwm/pwm-ep93xx.c
==============================================================================
TOPIC: documentation: Update circular buffer for load-acquire/store-release
http://groups.google.com/group/linux.kernel/t/9d3de39c23ef46a9?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:10 am
From: David Howells
Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> - /* read index before reading contents at that index */
> - smp_mb(); /* finish reading descriptor before incrementing tail */
I'd rather you didn't remove these comments (assuming they're correct) as
they're pointing out the point of the example.
David
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==============================================================================
TOPIC: of: make of_get_phy_mode parse 'phy-connection-type'
http://groups.google.com/group/linux.kernel/t/6029dafbccead828?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:30 am
From: Grant Likely
On Fri, 15 Nov 2013 06:23:32 +0000, Florian Fainelli <f.fainelli@gmail.com> wrote:
> Per the ePAPR v1.1 specification, 'phy-connection-type' is the canonical
> property name for describing an Ethernet to PHY connection type. Make
> sure that of_get_phy_mode() also attempts to parse that property and
> update the comments mentioning 'phy-mode' to also include
> 'phy-connection-type'.
>
> Acked-by: Grant Likely <grant.likely@linaro.org>
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Applied, thanks
g.
> ---
> Changes since v2:
> - reworked the error condition to look nicer per Grant's suggestion
> - added Grant's Acked-by tag
> - fixed a typo in the commit message on "mentioning"
>
> drivers/of/of_net.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/of/of_net.c b/drivers/of/of_net.c
> index 8f9be2e..651e249 100644
> --- a/drivers/of/of_net.c
> +++ b/drivers/of/of_net.c
> @@ -13,8 +13,8 @@
>
> /**
> * It maps 'enum phy_interface_t' found in include/linux/phy.h
> - * into the device tree binding of 'phy-mode', so that Ethernet
> - * device driver can get phy interface from device tree.
> + * into the device tree binding of 'phy-mode' or 'phy-connection-type',
> + * so that Ethernet device driver can get phy interface from device tree.
> */
> static const char *phy_modes[] = {
> [PHY_INTERFACE_MODE_NA] = "",
> @@ -36,8 +36,9 @@ static const char *phy_modes[] = {
> * of_get_phy_mode - Get phy mode for given device_node
> * @np: Pointer to the given device_node
> *
> - * The function gets phy interface string from property 'phy-mode',
> - * and return its index in phy_modes table, or errno in error case.
> + * The function gets phy interface string from property 'phy-mode' or
> + * 'phy-connection-type', and return its index in phy_modes table, or errno in
> + * error case.
> */
> int of_get_phy_mode(struct device_node *np)
> {
> @@ -46,6 +47,8 @@ int of_get_phy_mode(struct device_node *np)
>
> err = of_property_read_string(np, "phy-mode", &pm);
> if (err < 0)
> + err = of_property_read_string(np, "phy-connection-type", &pm);
> + if (err < 0)
> return err;
>
> for (i = 0; i < ARRAY_SIZE(phy_modes); i++)
> --
> 1.8.3.2
>
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==============================================================================
TOPIC: OF: Introduce utility helper functions
http://groups.google.com/group/linux.kernel/t/0531e1da074770e6?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:30 am
From: Pantelis Antoniou
Hi Grant,
On Nov 15, 2013, at 8:27 AM, Grant Likely wrote:
> On Thu, 14 Nov 2013 10:51:05 +0100, Pantelis Antoniou <panto@antoniou-consulting.com> wrote:
>> Hi Grant,
>>
>> On Nov 14, 2013, at 2:44 AM, Grant Likely wrote:
>>
>>> On Wed, 13 Nov 2013 10:03:37 +0100, Pantelis Antoniou <panto@antoniou-consulting.com> wrote:
>>>> On Nov 13, 2013, at 2:34 AM, Grant Likely wrote:
>>>>> On Tue, 12 Nov 2013 11:39:08 +0100, Pantelis Antoniou <panto@antoniou-consulting.com> wrote:
>>>>>>> On Tue, 5 Nov 2013 19:50:16 +0200, Pantelis Antoniou <panto@antoniou-consulting.com> wrote:
>>>>>>>> + } else {
>>>>>>>> + pr_warn("%s: node %p cannot be freed; memory is gone\n",
>>>>>>>> + __func__, node);
>>>>>>>> + }
>>>>>>>> +}
>>>>>>>
>>>>>>> All of the above is potentially dangerous. There is no way to determine
>>>>>>> if anything still holds a reference to a node. The proper way to handle
>>>>>>> removal of properties is to have a release method when the last
>>>>>>> of_node_put is called.
>>>>>>>
>>>>>>
>>>>>> This is safe, and expected to be called only on a dynamically created tree,
>>>>>> that's what all the checks against OF_DYNAMIC guard against.
>>>>>>
>>>>>> It is not ever meant to be called on an arbitrary tree, created by unflattening
>>>>>> a blob.
>>>>>
>>>>> I am talking about when being used on a dynamic tree. The problem is
>>>>> when a driver or other code holds a reference to a dynamic nodes, but
>>>>> doesn't release it correctly. The memory must not be freed until all of
>>>>> the references are relased. OF_DYNAMIC doesn't actually help in that
>>>>> case, and it is the reason for of_node_get()/of_node_put()
>>>>>
>>>>
>>>> I know, but even that is not enough. of_node_get()/of_node_put() handles the
>>>> case of references to the nodes, but not what happens with references to
>>>> properties. deadprops is mitigating the problem somewhat, but if we're going
>>>> to go to all the trouble of kobjectification let's do the props as well.
>>>>
>>>> of_get_property could be modified to return a devm_kmalloced copy of the real
>>>> property and that would deal with most of the callers. Of course for
>>>> the small sized scalar data we can avoid the copy.
>>>>
>>>> By using the devm_* interface we also avoid having to mess too much with the callers.
>>>>
>>>> I.e. what about something like devm_of_get_property()?
>>>
>>> Reference counting is already a horrible pain to keep correct. I don't
>>> see a better way to handle it in the dynamic case, so we're stuck with
>>> it, but I don't want to make it any harder. Adding ref counting to
>>> properties will make it harder than it already is to get the code right.
>>> I'm absolutely fine with a little bit of wasted memory in the form of
>>> deadprops when the alternative is so horrible. References at the node
>>> level is enough granularity.
>>>
>>> I don't think kduping the property is the solution either. I strongly
>>> suspect that will be far more expensive than the deadprop solution.
>>>
>>
>> As long as we can live with deadprops all is fine. Perhaps a devm_of_get_property()
>> makes sense for new drivers though? What do you think? Perhaps copying to a
>> user supplied buffer as well?
>
> I still don't think it is necessary. The device lifetime should always
> be shorter than the node lifetime.
>
>> It's a kind of drag. That means you get handed a device_node pointer you are not
>> able to free it without having the blob along with the container/accessor of it.
>> I.e. For the normal case where the blob comes from a request_firmware() call
>> You have to keep the firmware structure around.
>>
>> Depending on what other method you're going to use tends to make the code a little
>> bit messier.
>
> Understood. Stick with keeping the blob around for now. It can be
> reworkd in the future if necessary since there are no associated
> userspace ABI issues.
>
> g.
OK, will do.
Regards
-- Pantelis--
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==============================================================================
TOPIC: Documentation: gpiolib: document new interface
http://groups.google.com/group/linux.kernel/t/33a7b12a90958969?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:40 am
From: Alexandre Courbot
gpiolib now exports a new descriptor-based interface which deprecates
the older integer-based one. This patch documents this new interface and
also takes the opportunity to brush-up the GPIO documentation a little
bit.
The new descriptor-based interface follows the same consumer/driver
model as many other kernel subsystems (e.g. clock, regulator), so its
documentation has similarly been splitted into different files.
The content of the former documentation has been reused whenever it
made sense; however, some of its content did not apply to the new
interface anymore and have this been removed. Likewise, new sections
like the mapping of GPIOs to devices have been written from scratch.
The deprecated legacy-based documentation is still available, untouched,
under Documentation/gpio/gpio-legacy.txt.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
--
The first version received zero feedback, hopefully this one will get more
attention. :) Not much changes, just some more proofreading and the fixes
and improvements that came from it. It looks ok as far as I am concerned.
Linus, I hope this can be merged during the -rc cycle of 3.13, since the
gpiod_ interface is going to be introduced there. It would not make much
sense for it to come without its documentation.
---
Documentation/gpio.txt | 775 -------------------------------------
Documentation/gpio/board.txt | 115 ++++++
Documentation/gpio/consumer.txt | 197 ++++++++++
Documentation/gpio/driver.txt | 75 ++++
Documentation/gpio/gpio-legacy.txt | 775 +++++++++++++++++++++++++++++++++++++
Documentation/gpio/gpio.txt | 119 ++++++
Documentation/gpio/sysfs.txt | 155 ++++++++
7 files changed, 1436 insertions(+), 775 deletions(-)
delete mode 100644 Documentation/gpio.txt
create mode 100644 Documentation/gpio/board.txt
create mode 100644 Documentation/gpio/consumer.txt
create mode 100644 Documentation/gpio/driver.txt
create mode 100644 Documentation/gpio/gpio-legacy.txt
create mode 100644 Documentation/gpio/gpio.txt
create mode 100644 Documentation/gpio/sysfs.txt
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
deleted file mode 100644
index 6f83fa9..0000000
--- a/Documentation/gpio.txt
+++ /dev/null
@@ -1,775 +0,0 @@
-GPIO Interfaces
-
-This provides an overview of GPIO access conventions on Linux.
-
-These calls use the gpio_* naming prefix. No other calls should use that
-prefix, or the related __gpio_* prefix.
-
-
-What is a GPIO?
-===============
-A "General Purpose Input/Output" (GPIO) is a flexible software-controlled
-digital signal. They are provided from many kinds of chip, and are familiar
-to Linux developers working with embedded and custom hardware. Each GPIO
-represents a bit connected to a particular pin, or "ball" on Ball Grid Array
-(BGA) packages. Board schematics show which external hardware connects to
-which GPIOs. Drivers can be written generically, so that board setup code
-passes such pin configuration data to drivers.
-
-System-on-Chip (SOC) processors heavily rely on GPIOs. In some cases, every
-non-dedicated pin can be configured as a GPIO; and most chips have at least
-several dozen of them. Programmable logic devices (like FPGAs) can easily
-provide GPIOs; multifunction chips like power managers, and audio codecs
-often have a few such pins to help with pin scarcity on SOCs; and there are
-also "GPIO Expander" chips that connect using the I2C or SPI serial busses.
-Most PC southbridges have a few dozen GPIO-capable pins (with only the BIOS
-firmware knowing how they're used).
-
-The exact capabilities of GPIOs vary between systems. Common options:
-
- - Output values are writable (high=1, low=0). Some chips also have
- options about how that value is driven, so that for example only one
- value might be driven ... supporting "wire-OR" and similar schemes
- for the other value (notably, "open drain" signaling).
-
- - Input values are likewise readable (1, 0). Some chips support readback
- of pins configured as "output", which is very useful in such "wire-OR"
- cases (to support bidirectional signaling). GPIO controllers may have
- input de-glitch/debounce logic, sometimes with software controls.
-
- - Inputs can often be used as IRQ signals, often edge triggered but
- sometimes level triggered. Such IRQs may be configurable as system
- wakeup events, to wake the system from a low power state.
-
- - Usually a GPIO will be configurable as either input or output, as needed
- by different product boards; single direction ones exist too.
-
- - Most GPIOs can be accessed while holding spinlocks, but those accessed
- through a serial bus normally can't. Some systems support both types.
-
-On a given board each GPIO is used for one specific purpose like monitoring
-MMC/SD card insertion/removal, detecting card writeprotect status, driving
-a LED, configuring a transceiver, bitbanging a serial bus, poking a hardware
-watchdog, sensing a switch, and so on.
-
-
-GPIO conventions
-================
-Note that this is called a "convention" because you don't need to do it this
-way, and it's no crime if you don't. There **are** cases where portability
-is not the main issue; GPIOs are often used for the kind of board-specific
-glue logic that may even change between board revisions, and can't ever be
-used on a board that's wired differently. Only least-common-denominator
-functionality can be very portable. Other features are platform-specific,
-and that can be critical for glue logic.
-
-Plus, this doesn't require any implementation framework, just an interface.
-One platform might implement it as simple inline functions accessing chip
-registers; another might implement it by delegating through abstractions
-used for several very different kinds of GPIO controller. (There is some
-optional code supporting such an implementation strategy, described later
-in this document, but drivers acting as clients to the GPIO interface must
-not care how it's implemented.)
-
-That said, if the convention is supported on their platform, drivers should
-use it when possible. Platforms must select ARCH_REQUIRE_GPIOLIB or
-ARCH_WANT_OPTIONAL_GPIOLIB in their Kconfig. Drivers that can't work without
-standard GPIO calls should have Kconfig entries which depend on GPIOLIB. The
-GPIO calls are available, either as "real code" or as optimized-away stubs,
-when drivers use the include file:
-
- #include <linux/gpio.h>
-
-If you stick to this convention then it'll be easier for other developers to
-see what your code is doing, and help maintain it.
-
-Note that these operations include I/O barriers on platforms which need to
-use them; drivers don't need to add them explicitly.
-
-
-Identifying GPIOs
------------------
-GPIOs are identified by unsigned integers in the range 0..MAX_INT. That
-reserves "negative" numbers for other purposes like marking signals as
-"not available on this board", or indicating faults. Code that doesn't
-touch the underlying hardware treats these integers as opaque cookies.
-
-Platforms define how they use those integers, and usually #define symbols
-for the GPIO lines so that board-specific setup code directly corresponds
-to the relevant schematics. In contrast, drivers should only use GPIO
-numbers passed to them from that setup code, using platform_data to hold
-board-specific pin configuration data (along with other board specific
-data they need). That avoids portability problems.
-
-So for example one platform uses numbers 32-159 for GPIOs; while another
-uses numbers 0..63 with one set of GPIO controllers, 64-79 with another
-type of GPIO controller, and on one particular board 80-95 with an FPGA.
-The numbers need not be contiguous; either of those platforms could also
-use numbers 2000-2063 to identify GPIOs in a bank of I2C GPIO expanders.
-
-If you want to initialize a structure with an invalid GPIO number, use
-some negative number (perhaps "-EINVAL"); that will never be valid. To
-test if such number from such a structure could reference a GPIO, you
-may use this predicate:
-
- int gpio_is_valid(int number);
-
-A number that's not valid will be rejected by calls which may request
-or free GPIOs (see below). Other numbers may also be rejected; for
-example, a number might be valid but temporarily unused on a given board.
-
-Whether a platform supports multiple GPIO controllers is a platform-specific
-implementation issue, as are whether that support can leave "holes" in the space
-of GPIO numbers, and whether new controllers can be added at runtime. Such issues
-can affect things including whether adjacent GPIO numbers are both valid.
-
-Using GPIOs
------------
-The first thing a system should do with a GPIO is allocate it, using
-the gpio_request() call; see later.
-
-One of the next things to do with a GPIO, often in board setup code when
-setting up a platform_device using the GPIO, is mark its direction:
-
- /* set as input or output, returning 0 or negative errno */
- int gpio_direction_input(unsigned gpio);
- int gpio_direction_output(unsigned gpio, int value);
-
-The return value is zero for success, else a negative errno. It should
-be checked, since the get/set calls don't have error returns and since
-misconfiguration is possible. You should normally issue these calls from
-a task context. However, for spinlock-safe GPIOs it's OK to use them
-before tasking is enabled, as part of early board setup.
-
-For output GPIOs, the value provided becomes the initial output value.
-This helps avoid signal glitching during system startup.
-
-For compatibility with legacy interfaces to GPIOs, setting the direction
-of a GPIO implicitly requests that GPIO (see below) if it has not been
-requested already. That compatibility is being removed from the optional
-gpiolib framework.
-
-Setting the direction can fail if the GPIO number is invalid, or when
-that particular GPIO can't be used in that mode. It's generally a bad
-idea to rely on boot firmware to have set the direction correctly, since
-it probably wasn't validated to do more than boot Linux. (Similarly,
-that board setup code probably needs to multiplex that pin as a GPIO,
-and configure pullups/pulldowns appropriately.)
-
-
-Spinlock-Safe GPIO access
--------------------------
-Most GPIO controllers can be accessed with memory read/write instructions.
-Those don't need to sleep, and can safely be done from inside hard
-(nonthreaded) IRQ handlers and similar contexts.
-
-Use the following calls to access such GPIOs,
-for which gpio_cansleep() will always return false (see below):
-
- /* GPIO INPUT: return zero or nonzero */
- int gpio_get_value(unsigned gpio);
-
- /* GPIO OUTPUT */
- void gpio_set_value(unsigned gpio, int value);
-
-The values are boolean, zero for low, nonzero for high. When reading the
-value of an output pin, the value returned should be what's seen on the
-pin ... that won't always match the specified output value, because of
-issues including open-drain signaling and output latencies.
-
-The get/set calls have no error returns because "invalid GPIO" should have
-been reported earlier from gpio_direction_*(). However, note that not all
-platforms can read the value of output pins; those that can't should always
-return zero. Also, using these calls for GPIOs that can't safely be accessed
-without sleeping (see below) is an error.
-
-Platform-specific implementations are encouraged to optimize the two
-calls to access the GPIO value in cases where the GPIO number (and for
-output, value) are constant. It's normal for them to need only a couple
-of instructions in such cases (reading or writing a hardware register),
-and not to need spinlocks. Such optimized calls can make bitbanging
-applications a lot more efficient (in both space and time) than spending
-dozens of instructions on subroutine calls.
-
-
-GPIO access that may sleep
---------------------------
-Some GPIO controllers must be accessed using message based busses like I2C
-or SPI. Commands to read or write those GPIO values require waiting to
-get to the head of a queue to transmit a command and get its response.
-This requires sleeping, which can't be done from inside IRQ handlers.
-
-Platforms that support this type of GPIO distinguish them from other GPIOs
-by returning nonzero from this call (which requires a valid GPIO number,
-which should have been previously allocated with gpio_request):
-
- int gpio_cansleep(unsigned gpio);
-
-To access such GPIOs, a different set of accessors is defined:
-
- /* GPIO INPUT: return zero or nonzero, might sleep */
- int gpio_get_value_cansleep(unsigned gpio);
-
- /* GPIO OUTPUT, might sleep */
- void gpio_set_value_cansleep(unsigned gpio, int value);
-
-
-Accessing such GPIOs requires a context which may sleep, for example
-a threaded IRQ handler, and those accessors must be used instead of
-spinlock-safe accessors without the cansleep() name suffix.
-
-Other than the fact that these accessors might sleep, and will work
-on GPIOs that can't be accessed from hardIRQ handlers, these calls act
-the same as the spinlock-safe calls.
-
- ** IN ADDITION ** calls to setup and configure such GPIOs must be made
-from contexts which may sleep, since they may need to access the GPIO
-controller chip too: (These setup calls are usually made from board
-setup or driver probe/teardown code, so this is an easy constraint.)
-
- gpio_direction_input()
- gpio_direction_output()
- gpio_request()
-
-## gpio_request_one()
-## gpio_request_array()
-## gpio_free_array()
-
- gpio_free()
- gpio_set_debounce()
-
-
-
-Claiming and Releasing GPIOs
-----------------------------
-To help catch system configuration errors, two calls are defined.
-
- /* request GPIO, returning 0 or negative errno.
- * non-null labels may be useful for diagnostics.
- */
- int gpio_request(unsigned gpio, const char *label);
-
- /* release previously-claimed GPIO */
- void gpio_free(unsigned gpio);
-
-Passing invalid GPIO numbers to gpio_request() will fail, as will requesting
-GPIOs that have already been claimed with that call. The return value of
-gpio_request() must be checked. You should normally issue these calls from
-a task context. However, for spinlock-safe GPIOs it's OK to request GPIOs
-before tasking is enabled, as part of early board setup.
-
-These calls serve two basic purposes. One is marking the signals which
-are actually in use as GPIOs, for better diagnostics; systems may have
-several hundred potential GPIOs, but often only a dozen are used on any
-given board. Another is to catch conflicts, identifying errors when
-(a) two or more drivers wrongly think they have exclusive use of that
-signal, or (b) something wrongly believes it's safe to remove drivers
-needed to manage a signal that's in active use. That is, requesting a
-GPIO can serve as a kind of lock.
-
-Some platforms may also use knowledge about what GPIOs are active for
-power management, such as by powering down unused chip sectors and, more
-easily, gating off unused clocks.
-
-For GPIOs that use pins known to the pinctrl subsystem, that subsystem should
-be informed of their use; a gpiolib driver's .request() operation may call
-pinctrl_request_gpio(), and a gpiolib driver's .free() operation may call
-pinctrl_free_gpio(). The pinctrl subsystem allows a pinctrl_request_gpio()
-to succeed concurrently with a pin or pingroup being "owned" by a device for
-pin multiplexing.
-
-Any programming of pin multiplexing hardware that is needed to route the
-GPIO signal to the appropriate pin should occur within a GPIO driver's
-.direction_input() or .direction_output() operations, and occur after any
-setup of an output GPIO's value. This allows a glitch-free migration from a
-pin's special function to GPIO. This is sometimes required when using a GPIO
-to implement a workaround on signals typically driven by a non-GPIO HW block.
-
-Some platforms allow some or all GPIO signals to be routed to different pins.
-Similarly, other aspects of the GPIO or pin may need to be configured, such as
-pullup/pulldown. Platform software should arrange that any such details are
-configured prior to gpio_request() being called for those GPIOs, e.g. using
-the pinctrl subsystem's mapping table, so that GPIO users need not be aware
-of these details.
-
-Also note that it's your responsibility to have stopped using a GPIO
-before you free it.
-
-Considering in most cases GPIOs are actually configured right after they
-are claimed, three additional calls are defined:
-
- /* request a single GPIO, with initial configuration specified by
- * 'flags', identical to gpio_request() wrt other arguments and
- * return value
- */
- int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
-
- /* request multiple GPIOs in a single call
- */
- int gpio_request_array(struct gpio *array, size_t num);
-
- /* release multiple GPIOs in a single call
- */
- void gpio_free_array(struct gpio *array, size_t num);
-
-where 'flags' is currently defined to specify the following properties:
-
- * GPIOF_DIR_IN - to configure direction as input
- * GPIOF_DIR_OUT - to configure direction as output
-
- * GPIOF_INIT_LOW - as output, set initial level to LOW
- * GPIOF_INIT_HIGH - as output, set initial level to HIGH
- * GPIOF_OPEN_DRAIN - gpio pin is open drain type.
- * GPIOF_OPEN_SOURCE - gpio pin is open source type.
-
- * GPIOF_EXPORT_DIR_FIXED - export gpio to sysfs, keep direction
- * GPIOF_EXPORT_DIR_CHANGEABLE - also export, allow changing direction
-
-since GPIOF_INIT_* are only valid when configured as output, so group valid
-combinations as:
-
- * GPIOF_IN - configure as input
- * GPIOF_OUT_INIT_LOW - configured as output, initial level LOW
- * GPIOF_OUT_INIT_HIGH - configured as output, initial level HIGH
-
-When setting the flag as GPIOF_OPEN_DRAIN then it will assume that pins is
-open drain type. Such pins will not be driven to 1 in output mode. It is
-require to connect pull-up on such pins. By enabling this flag, gpio lib will
-make the direction to input when it is asked to set value of 1 in output mode
-to make the pin HIGH. The pin is make to LOW by driving value 0 in output mode.
-
-When setting the flag as GPIOF_OPEN_SOURCE then it will assume that pins is
-open source type. Such pins will not be driven to 0 in output mode. It is
-require to connect pull-down on such pin. By enabling this flag, gpio lib will
-make the direction to input when it is asked to set value of 0 in output mode
-to make the pin LOW. The pin is make to HIGH by driving value 1 in output mode.
-
-In the future, these flags can be extended to support more properties.
-
-Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
-introduced to encapsulate all three fields as:
-
- struct gpio {
- unsigned gpio;
- unsigned long flags;
- const char *label;
- };
-
-A typical example of usage:
-
- static struct gpio leds_gpios[] = {
- { 32, GPIOF_OUT_INIT_HIGH, "Power LED" }, /* default to ON */
- { 33, GPIOF_OUT_INIT_LOW, "Green LED" }, /* default to OFF */
- { 34, GPIOF_OUT_INIT_LOW, "Red LED" }, /* default to OFF */
- { 35, GPIOF_OUT_INIT_LOW, "Blue LED" }, /* default to OFF */
- { ... },
- };
-
- err = gpio_request_one(31, GPIOF_IN, "Reset Button");
- if (err)
- ...
-
- err = gpio_request_array(leds_gpios, ARRAY_SIZE(leds_gpios));
- if (err)
- ...
-
- gpio_free_array(leds_gpios, ARRAY_SIZE(leds_gpios));
-
-
-GPIOs mapped to IRQs
---------------------
-GPIO numbers are unsigned integers; so are IRQ numbers. These make up
-two logically distinct namespaces (GPIO 0 need not use IRQ 0). You can
-map between them using calls like:
-
- /* map GPIO numbers to IRQ numbers */
- int gpio_to_irq(unsigned gpio);
-
- /* map IRQ numbers to GPIO numbers (avoid using this) */
- int irq_to_gpio(unsigned irq);
-
-Those return either the corresponding number in the other namespace, or
-else a negative errno code if the mapping can't be done. (For example,
-some GPIOs can't be used as IRQs.) It is an unchecked error to use a GPIO
-number that wasn't set up as an input using gpio_direction_input(), or
-to use an IRQ number that didn't originally come from gpio_to_irq().
-
-These two mapping calls are expected to cost on the order of a single
-addition or subtraction. They're not allowed to sleep.
-
-Non-error values returned from gpio_to_irq() can be passed to request_irq()
-or free_irq(). They will often be stored into IRQ resources for platform
-devices, by the board-specific initialization code. Note that IRQ trigger
-options are part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are
-system wakeup capabilities.
-
-Non-error values returned from irq_to_gpio() would most commonly be used
-with gpio_get_value(), for example to initialize or update driver state
-when the IRQ is edge-triggered. Note that some platforms don't support
-this reverse mapping, so you should avoid using it.
-
-
-Emulating Open Drain Signals
-----------------------------
-Sometimes shared signals need to use "open drain" signaling, where only the
-low signal level is actually driven. (That term applies to CMOS transistors;
-"open collector" is used for TTL.) A pullup resistor causes the high signal
-level. This is sometimes called a "wire-AND"; or more practically, from the
-negative logic (low=true) perspective this is a "wire-OR".
-
-One common example of an open drain signal is a shared active-low IRQ line.
-Also, bidirectional data bus signals sometimes use open drain signals.
-
-Some GPIO controllers directly support open drain outputs; many don't. When
-you need open drain signaling but your hardware doesn't directly support it,
-there's a common idiom you can use to emulate it with any GPIO pin that can
-be used as either an input or an output:
-
- LOW: gpio_direction_output(gpio, 0) ... this drives the signal
- and overrides the pullup.
-
- HIGH: gpio_direction_input(gpio) ... this turns off the output,
- so the pullup (or some other device) controls the signal.
-
-If you are "driving" the signal high but gpio_get_value(gpio) reports a low
-value (after the appropriate rise time passes), you know some other component
-is driving the shared signal low. That's not necessarily an error. As one
-common example, that's how I2C clocks are stretched: a slave that needs a
-slower clock delays the rising edge of SCK, and the I2C master adjusts its
-signaling rate accordingly.
-
-
-GPIO controllers and the pinctrl subsystem
-------------------------------------------
-
-A GPIO controller on a SOC might be tightly coupled with the pinctrl
-subsystem, in the sense that the pins can be used by other functions
-together with an optional gpio feature. We have already covered the
-case where e.g. a GPIO controller need to reserve a pin or set the
-direction of a pin by calling any of:
-
-pinctrl_request_gpio()
-pinctrl_free_gpio()
-pinctrl_gpio_direction_input()
-pinctrl_gpio_direction_output()
-
-But how does the pin control subsystem cross-correlate the GPIO
-numbers (which are a global business) to a certain pin on a certain
-pin controller?
-
-This is done by registering "ranges" of pins, which are essentially
-cross-reference tables. These are described in
-Documentation/pinctrl.txt
-
-While the pin allocation is totally managed by the pinctrl subsystem,
-gpio (under gpiolib) is still maintained by gpio drivers. It may happen
-that different pin ranges in a SoC is managed by different gpio drivers.
-
-This makes it logical to let gpio drivers announce their pin ranges to
-the pin ctrl subsystem before it will call 'pinctrl_request_gpio' in order
-to request the corresponding pin to be prepared by the pinctrl subsystem
-before any gpio usage.
-
-For this, the gpio controller can register its pin range with pinctrl
-subsystem. There are two ways of doing it currently: with or without DT.
-
-For with DT support refer to Documentation/devicetree/bindings/gpio/gpio.txt.
-
-For non-DT support, user can call gpiochip_add_pin_range() with appropriate
-parameters to register a range of gpio pins with a pinctrl driver. For this
-exact name string of pinctrl device has to be passed as one of the
-argument to this routine.
-
-
-What do these conventions omit?
-===============================
-One of the biggest things these conventions omit is pin multiplexing, since
-this is highly chip-specific and nonportable. One platform might not need
-explicit multiplexing; another might have just two options for use of any
-given pin; another might have eight options per pin; another might be able
-to route a given GPIO to any one of several pins. (Yes, those examples all
-come from systems that run Linux today.)
-
-Related to multiplexing is configuration and enabling of the pullups or
-pulldowns integrated on some platforms. Not all platforms support them,
-or support them in the same way; and any given board might use external
-pullups (or pulldowns) so that the on-chip ones should not be used.
-(When a circuit needs 5 kOhm, on-chip 100 kOhm resistors won't do.)
-Likewise drive strength (2 mA vs 20 mA) and voltage (1.8V vs 3.3V) is a
-platform-specific issue, as are models like (not) having a one-to-one
-correspondence between configurable pins and GPIOs.
-
-There are other system-specific mechanisms that are not specified here,
-like the aforementioned options for input de-glitching and wire-OR output.
-Hardware may support reading or writing GPIOs in gangs, but that's usually
-configuration dependent: for GPIOs sharing the same bank. (GPIOs are
-commonly grouped in banks of 16 or 32, with a given SOC having several such
-banks.) Some systems can trigger IRQs from output GPIOs, or read values
-from pins not managed as GPIOs. Code relying on such mechanisms will
-necessarily be nonportable.
-
-Dynamic definition of GPIOs is not currently standard; for example, as
-a side effect of configuring an add-on board with some GPIO expanders.
-
-
-GPIO implementor's framework (OPTIONAL)
-=======================================
-As noted earlier, there is an optional implementation framework making it
-easier for platforms to support different kinds of GPIO controller using
-the same programming interface. This framework is called "gpiolib".
-
-As a debugging aid, if debugfs is available a /sys/kernel/debug/gpio file
-will be found there. That will list all the controllers registered through
-this framework, and the state of the GPIOs currently in use.
-
-
-Controller Drivers: gpio_chip
------------------------------
-In this framework each GPIO controller is packaged as a "struct gpio_chip"
-with information common to each controller of that type:
-
- - methods to establish GPIO direction
- - methods used to access GPIO values
- - flag saying whether calls to its methods may sleep
- - optional debugfs dump method (showing extra state like pullup config)
- - label for diagnostics
-
-There is also per-instance data, which may come from device.platform_data:
-the number of its first GPIO, and how many GPIOs it exposes.
-
-The code implementing a gpio_chip should support multiple instances of the
-controller, possibly using the driver model. That code will configure each
-gpio_chip and issue gpiochip_add(). Removing a GPIO controller should be
-rare; use gpiochip_remove() when it is unavoidable.
-
-Most often a gpio_chip is part of an instance-specific structure with state
-not exposed by the GPIO interfaces, such as addressing, power management,
-and more. Chips such as codecs will have complex non-GPIO state.
-
-Any debugfs dump method should normally ignore signals which haven't been
-requested as GPIOs. They can use gpiochip_is_requested(), which returns
-either NULL or the label associated with that GPIO when it was requested.
-
-
-Platform Support
-----------------
-To support this framework, a platform's Kconfig will "select" either
-ARCH_REQUIRE_GPIOLIB or ARCH_WANT_OPTIONAL_GPIOLIB
-and arrange that its <asm/gpio.h> includes <asm-generic/gpio.h> and defines
-three functions: gpio_get_value(), gpio_set_value(), and gpio_cansleep().
-
-It may also provide a custom value for ARCH_NR_GPIOS, so that it better
-reflects the number of GPIOs in actual use on that platform, without
-wasting static table space. (It should count both built-in/SoC GPIOs and
-also ones on GPIO expanders.
-
-ARCH_REQUIRE_GPIOLIB means that the gpiolib code will always get compiled
-into the kernel on that architecture.
-
-ARCH_WANT_OPTIONAL_GPIOLIB means the gpiolib code defaults to off and the user
-can enable it and build it into the kernel optionally.
-
-If neither of these options are selected, the platform does not support
-GPIOs through GPIO-lib and the code cannot be enabled by the user.
-
-Trivial implementations of those functions can directly use framework
-code, which always dispatches through the gpio_chip:
-
- #define gpio_get_value __gpio_get_value
- #define gpio_set_value __gpio_set_value
- #define gpio_cansleep __gpio_cansleep
-
-Fancier implementations could instead define those as inline functions with
-logic optimizing access to specific SOC-based GPIOs. For example, if the
-referenced GPIO is the constant "12", getting or setting its value could
-cost as little as two or three instructions, never sleeping. When such an
-optimization is not possible those calls must delegate to the framework
-code, costing at least a few dozen instructions. For bitbanged I/O, such
-instruction savings can be significant.
-
-For SOCs, platform-specific code defines and registers gpio_chip instances
-for each bank of on-chip GPIOs. Those GPIOs should be numbered/labeled to
-match chip vendor documentation, and directly match board schematics. They
-may well start at zero and go up to a platform-specific limit. Such GPIOs
-are normally integrated into platform initialization to make them always be
-available, from arch_initcall() or earlier; they can often serve as IRQs.
-
-
-Board Support
--------------
-For external GPIO controllers -- such as I2C or SPI expanders, ASICs, multi
-function devices, FPGAs or CPLDs -- most often board-specific code handles
-registering controller devices and ensures that their drivers know what GPIO
-numbers to use with gpiochip_add(). Their numbers often start right after
-platform-specific GPIOs.
-
-For example, board setup code could create structures identifying the range
-of GPIOs that chip will expose, and passes them to each GPIO expander chip
-using platform_data. Then the chip driver's probe() routine could pass that
-data to gpiochip_add().
-
-Initialization order can be important. For example, when a device relies on
-an I2C-based GPIO, its probe() routine should only be called after that GPIO
-becomes available. That may mean the device should not be registered until
-calls for that GPIO can work. One way to address such dependencies is for
-such gpio_chip controllers to provide setup() and teardown() callbacks to
-board specific code; those board specific callbacks would register devices
-once all the necessary resources are available, and remove them later when
-the GPIO controller device becomes unavailable.
-
-
-Sysfs Interface for Userspace (OPTIONAL)
-========================================
-Platforms which use the "gpiolib" implementors framework may choose to
-configure a sysfs user interface to GPIOs. This is different from the
-debugfs interface, since it provides control over GPIO direction and
-value instead of just showing a gpio state summary. Plus, it could be
-present on production systems without debugging support.
-
-Given appropriate hardware documentation for the system, userspace could
-know for example that GPIO #23 controls the write protect line used to
-protect boot loader segments in flash memory. System upgrade procedures
-may need to temporarily remove that protection, first importing a GPIO,
-then changing its output state, then updating the code before re-enabling
-the write protection. In normal use, GPIO #23 would never be touched,
-and the kernel would have no need to know about it.
-
-Again depending on appropriate hardware documentation, on some systems
-userspace GPIO can be used to determine system configuration data that
-standard kernels won't know about. And for some tasks, simple userspace
-GPIO drivers could be all that the system really needs.
-
-Note that standard kernel drivers exist for common "LEDs and Buttons"
-GPIO tasks: "leds-gpio" and "gpio_keys", respectively. Use those
-instead of talking directly to the GPIOs; they integrate with kernel
-frameworks better than your userspace code could.
-
-
-Paths in Sysfs
---------------
-There are three kinds of entry in /sys/class/gpio:
-
- - Control interfaces used to get userspace control over GPIOs;
-
- - GPIOs themselves; and
-
- - GPIO controllers ("gpio_chip" instances).
-
-That's in addition to standard files including the "device" symlink.
-
-The control interfaces are write-only:
-
- /sys/class/gpio/
-
- "export" ... Userspace may ask the kernel to export control of
- a GPIO to userspace by writing its number to this file.
-
- Example: "echo 19 > export" will create a "gpio19" node
- for GPIO #19, if that's not requested by kernel code.
-
- "unexport" ... Reverses the effect of exporting to userspace.
-
- Example: "echo 19 > unexport" will remove a "gpio19"
- node exported using the "export" file.
-
-GPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42)
-and have the following read/write attributes:
-
- /sys/class/gpio/gpioN/
-
- "direction" ... reads as either "in" or "out". This value may
- normally be written. Writing as "out" defaults to
- initializing the value as low. To ensure glitch free
- operation, values "low" and "high" may be written to
- configure the GPIO as an output with that initial value.
-
- Note that this attribute *will not exist* if the kernel
- doesn't support changing the direction of a GPIO, or
- it was exported by kernel code that didn't explicitly
- allow userspace to reconfigure this GPIO's direction.
-
- "value" ... reads as either 0 (low) or 1 (high). If the GPIO
- is configured as an output, this value may be written;
- any nonzero value is treated as high.
-
- If the pin can be configured as interrupt-generating interrupt
- and if it has been configured to generate interrupts (see the
- description of "edge"), you can poll(2) on that file and
- poll(2) will return whenever the interrupt was triggered. If
- you use poll(2), set the events POLLPRI and POLLERR. If you
- use select(2), set the file descriptor in exceptfds. After
- poll(2) returns, either lseek(2) to the beginning of the sysfs
- file and read the new value or close the file and re-open it
- to read the value.
-
- "edge" ... reads as either "none", "rising", "falling", or
- "both". Write these strings to select the signal edge(s)
- that will make poll(2) on the "value" file return.
-
- This file exists only if the pin can be configured as an
- interrupt generating input pin.
-
- "active_low" ... reads as either 0 (false) or 1 (true). Write
- any nonzero value to invert the value attribute both
- for reading and writing. Existing and subsequent
- poll(2) support configuration via the edge attribute
- for "rising" and "falling" edges will follow this
- setting.
-
-GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
-controller implementing GPIOs starting at #42) and have the following
-read-only attributes:
-
- /sys/class/gpio/gpiochipN/
-
- "base" ... same as N, the first GPIO managed by this chip
-
- "label" ... provided for diagnostics (not always unique)
-
- "ngpio" ... how many GPIOs this manges (N to N + ngpio - 1)
-
-Board documentation should in most cases cover what GPIOs are used for
-what purposes. However, those numbers are not always stable; GPIOs on
-a daughtercard might be different depending on the base board being used,
-or other cards in the stack. In such cases, you may need to use the
-gpiochip nodes (possibly in conjunction with schematics) to determine
-the correct GPIO number to use for a given signal.
-
-
-Exporting from Kernel code
---------------------------
-Kernel code can explicitly manage exports of GPIOs which have already been
-requested using gpio_request():
-
- /* export the GPIO to userspace */
- int gpio_export(unsigned gpio, bool direction_may_change);
-
- /* reverse gpio_export() */
- void gpio_unexport();
-
- /* create a sysfs link to an exported GPIO node */
- int gpio_export_link(struct device *dev, const char *name,
- unsigned gpio)
-
- /* change the polarity of a GPIO node in sysfs */
- int gpio_sysfs_set_active_low(unsigned gpio, int value);
-
-After a kernel driver requests a GPIO, it may only be made available in
-the sysfs interface by gpio_export(). The driver can control whether the
-signal direction may change. This helps drivers prevent userspace code
-from accidentally clobbering important system state.
-
-This explicit exporting can help with debugging (by making some kinds
-of experiments easier), or can provide an always-there interface that's
-suitable for documenting as part of a board support package.
-
-After the GPIO has been exported, gpio_export_link() allows creating
-symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
-use this to provide the interface under their own device in sysfs with
-a descriptive name.
-
-Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity
-differences between boards from user space. This only affects the
-sysfs interface. Polarity change can be done both before and after
-gpio_export(), and previously enabled poll(2) support for either
-rising or falling edge will be reconfigured to follow this setting.
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt
new file mode 100644
index 0000000..0d03506
--- /dev/null
+++ b/Documentation/gpio/board.txt
@@ -0,0 +1,115 @@
+GPIO Mappings
+=============
+
+This document explains how GPIOs can be assigned to given devices and functions.
+Note that it only applies to the new descriptor-based interface. For a
+description of the deprecated integer-based GPIO interface please refer to
+gpio-legacy.txt (actually, there is no real mapping possible with the old
+interface; you just fetch an integer from somewhere and request the
+corresponding GPIO.
+
+Platforms that make use of GPIOs must select ARCH_REQUIRE_GPIOLIB (if GPIO usage
+is mandatory) or ARCH_WANT_OPTIONAL_GPIOLIB (if GPIO support can be omitted) in
+their Kconfig. Then, how GPIOs are mapped depends on what the platform uses to
+describe its hardware layout. Currently, mappings can be defined through device
+tree, ACPI, and platform data.
+
+Device Tree
+-----------
+GPIOs can easily be mapped to devices and functions in the device tree. The
+exact way to do it depends on the GPIO controller providing the GPIOs, see the
+device tree bindings for your controller.
+
+GPIOs mappings are defined in the consumer device's node, in a property named
+<function>-gpios, where <function> is the function the driver will request
+through gpiod_get(). For example:
+
+ foo_device {
+ compatible = "acme,foo";
+ ...
+ led-gpios = <&gpio 15 GPIO_ACTIVE_HIGH>, /* red */
+ <&gpio 16 GPIO_ACTIVE_HIGH>, /* green */
+ <&gpio 17 GPIO_ACTIVE_HIGH>; /* blue */
+
+ power-gpio = <&gpio 1 GPIO_ACTIVE_LOW>;
+ };
+
+This property will make GPIOs 15, 16 and 17 available to the driver under the
+"led" function, and GPIO 1 as the "power" GPIO:
+
+ struct gpio_desc *red, *green, *blue, *power;
+
+ red = gpiod_get_index(dev, "led", 0);
+ green = gpiod_get_index(dev, "led", 1);
+ blue = gpiod_get_index(dev, "led", 2);
+
+ power = gpiod_get(dev, "power");
+
+The led GPIOs will be active-high, while the power GPIO will be active-low (i.e.
+gpiod_is_active_low(power) will be true).
+
+ACPI
+----
+ACPI does not support function names for GPIOs. Therefore, only the "idx"
+argument of gpiod_get_index() is useful to discriminate between GPIOs assigned
+to a device. The "con_id" argument can still be set for debugging purposes (it
+will appear under error messages as well as debug and sysfs nodes).
+
+Platform Data
+-------------
+Finally, GPIOs can be bound to devices and functions using platform data. Board
+files that desire to do so need to include the following header:
+
+ #include <linux/gpio/driver.h>
+
+GPIOs are mapped by the means of tables of lookups, containing instances of the
+gpiod_lookup structure. Two macros are defined to help declaring such mappings:
+
+ GPIO_LOOKUP(chip_label, chip_hwnum, dev_id, con_id, flags)
+ GPIO_LOOKUP_IDX(chip_label, chip_hwnum, dev_id, con_id, idx, flags)
+
+where
+
+ - chip_label is the label of the gpiod_chip instance providing the GPIO
+ - chip_hwnum is the hardware number of the GPIO within the chip
+ - dev_id is the identifier of the device that will make use of this GPIO. If
+ NULL, the GPIO will be available to all devices.
+ - con_id is the name of the GPIO function from the device point of view. It
+ can be NULL.
+ - idx is the index of the GPIO within the function.
+ - flags is defined to specify the following properties:
+ * GPIOF_ACTIVE_LOW - to configure the GPIO as active-low
+ * GPIOF_OPEN_DRAIN - GPIO pin is open drain type.
+ * GPIOF_OPEN_SOURCE - GPIO pin is open source type.
+
+In the future, these flags might be extended to support more properties.
+
+Note that GPIO_LOOKUP() is just a shortcut to GPIO_LOOKUP_IDX() where idx = 0.
+
+A lookup table can then be defined as follows:
+
+ struct gpiod_lookup gpios_table[] = {
+ GPIO_LOOKUP_IDX("gpio.0", 15, "foo.0", "led", 0, GPIO_ACTIVE_HIGH),
+ GPIO_LOOKUP_IDX("gpio.0", 16, "foo.0", "led", 1, GPIO_ACTIVE_HIGH),
+ GPIO_LOOKUP_IDX("gpio.0", 17, "foo.0", "led", 2, GPIO_ACTIVE_HIGH),
+ GPIO_LOOKUP("gpio.0", 1, "foo.0", "power", GPIO_ACTIVE_LOW),
+ };
+
+And the table can be added by the board code as follows:
+
+ gpiod_add_table(gpios_table, ARRAY_SIZE(gpios_table));
+
+The driver controlling "foo.0" will then be able to obtain its GPIOs as follows:
+
+ struct gpio_desc *red, *green, *blue, *power;
+
+ red = gpiod_get_index(dev, "led", 0);
+ green = gpiod_get_index(dev, "led", 1);
+ blue = gpiod_get_index(dev, "led", 2);
+
+ power = gpiod_get(dev, "power");
+ gpiod_direction_output(power, 1);
+
+Since the "power" GPIO is mapped as active-low, its actual signal will be 0
+after this code. Contrary to the legacy integer GPIO interface, the active-low
+property is handled during mapping and is thus transparent to GPIO consumers.
diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
new file mode 100644
index 0000000..3bb3c48
--- /dev/null
+++ b/Documentation/gpio/consumer.txt
@@ -0,0 +1,197 @@
+GPIO Descriptor Consumer Interface
+==================================
+
+This document describes the consumer interface of the GPIO framework. Note that
+it describes the new descriptor-based interface. For a description of the
+deprecated integer-based GPIO interface please refer to gpio-legacy.txt.
+
+
+Guidelines for GPIOs consumers
+==============================
+
+Drivers that can't work without standard GPIO calls should have Kconfig entries
+that depend on GPIOLIB. The functions that allow a driver to obtain and use
+GPIOs are available by including the following file:
+
+ #include <linux/gpio/consumer.h>
+
+All the functions that work with the descriptor-based GPIO interface are
+prefixed with gpiod_. The gpio_ prefix is used for the legacy interface. No
+other function in the kernel should use these prefixes.
+
+
+Obtaining and Disposing GPIOs
+=============================
+
+With the descriptor-based interface, GPIOs are identified with an opaque,
+non-forgeable handler that must be obtained through a call to one of the
+gpiod_get() functions. Like many other kernel subsystems, gpiod_get() takes the
+device that will use the GPIO and the function the requested GPIO is supposed to
+fulfill:
+
+ struct gpio_desc *gpiod_get(struct device *dev, const char *con_id)
+
+If a function is implemented by using several GPIOs together (e.g. a simple LED
+device that displays digits), an additional index argument can be specified:
+
+ struct gpio_desc *gpiod_get_index(struct device *dev,
+ const char *con_id, unsigned int idx)
+
+Both functions return either a valid GPIO descriptor, or an error code checkable
+with IS_ERR(). They will never return a NULL pointer.
+
+Device-managed variants of these functions are also defined:
+
+ struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id)
+
+ struct gpio_desc *devm_gpiod_get_index(struct device *dev,
+ const char *con_id,
+ unsigned int idx)
+
+A GPIO descriptor can be disposed of using the gpiod_put() function:
+
+ void gpiod_put(struct gpio_desc *desc)
+
+It is strictly forbidden to use a descriptor after calling this function. The
+device-managed variant is, unsurprisingly:
+
+ void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
+
+
+Using GPIOs
+===========
+
+Setting Direction
+-----------------
+The first thing a driver must do with a GPIO is setting its direction. This is
+done by invoking one of the gpiod_direction_*() functions:
+
+ int gpiod_direction_input(struct gpio_desc *desc)
+ int gpiod_direction_output(struct gpio_desc *desc, int value)
+
+The return value is zero for success, else a negative errno. It should be
+checked, since the get/set calls don't return errors and since misconfiguration
+is possible. You should normally issue these calls from a task context. However,
+for spinlock-safe GPIOs it is OK to use them before tasking is enabled, as part
+of early board setup.
+
+For output GPIOs, the value provided becomes the initial output value. This
+helps avoid signal glitching during system startup.
+
+A driver can also query the current direction of a GPIO:
+
+ int gpiod_get_direction(const struct gpio_desc *desc)
+
+This function will return either GPIOF_DIR_IN or GPIOF_DIR_OUT.
+
+Be aware that there is no default direction for GPIOs. Therefore, **using a GPIO
+without setting its direction first is illegal and will result in undefined
+behavior!**
+
+
+Spinlock-Safe GPIO Access
+-------------------------
+Most GPIO controllers can be accessed with memory read/write instructions. Those
+don't need to sleep, and can safely be done from inside hard (non-threaded) IRQ
+handlers and similar contexts.
+
+Use the following calls to access GPIOs from an atomic context:
+
+ int gpiod_get_value(const struct gpio_desc *desc);
+ void gpiod_set_value(struct gpio_desc *desc, int value);
+
+The values are boolean, zero for low, nonzero for high. When reading the value
+of an output pin, the value returned should be what's seen on the pin. That
+won't always match the specified output value, because of issues including
+open-drain signaling and output latencies.
+
+The get/set calls do not return errors because "invalid GPIO" should have been
+reported earlier from gpiod_direction_*(). However, note that not all platforms
+can read the value of output pins; those that can't should always return zero.
+Also, using these calls for GPIOs that can't safely be accessed without sleeping
+(see below) is an error.
+
+
+GPIO Access That May Sleep
+--------------------------
+Some GPIO controllers must be accessed using message based buses like I2C or
+SPI. Commands to read or write those GPIO values require waiting to get to the
+head of a queue to transmit a command and get its response. This requires
+sleeping, which can't be done from inside IRQ handlers.
+
+Platforms that support this type of GPIO distinguish them from other GPIOs by
+returning nonzero from this call:
+
+ int gpiod_cansleep(const struct gpio_desc *desc)
+
+To access such GPIOs, a different set of accessors is defined:
+
+ int gpiod_get_value_cansleep(const struct gpio_desc *desc)
+ void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
+
+Accessing such GPIOs requires a context which may sleep, for example a threaded
+IRQ handler, and those accessors must be used instead of spinlock-safe
+accessors without the cansleep() name suffix.
+
+Other than the fact that these accessors might sleep, and will work on GPIOs
+that can't be accessed from hardIRQ handlers, these calls act the same as the
+spinlock-safe calls.
+
+
+Active-low State and Raw GPIO Values
+------------------------------------
+Device drivers like to manage the logical state of a GPIO, i.e. the value their
+device will actually receive, no matter what lies between it and the GPIO line.
+In some cases, it might make sense to control the actual GPIO line value. The
+following set of calls ignore the active-low property of a GPIO and work on the
+raw line value:
+
+ int gpiod_get_raw_value(const struct gpio_desc *desc)
+ void gpiod_set_raw_value(struct gpio_desc *desc, int value)
+ int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc)
+ void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value)
+
+The active-low state of a GPIO can also be queried using the following call:
+
+ int gpiod_is_active_low(const struct gpio_desc *desc)
+
+Note that these functions should only be used with great moderation ; a driver
+should not have to care about the physical line level.
+
+GPIOs mapped to IRQs
+--------------------
+GPIO lines can quite often be used as IRQs. You can get the IRQ number
+corresponding to a given GPIO using the following call:
+
+ int gpiod_to_irq(const struct gpio_desc *desc)
+
+It will return an IRQ number, or an negative errno code if the mapping can't be
+done (most likely because that particular GPIO cannot be used as IRQ). It is an
+unchecked error to use a GPIO that wasn't set up as an input using
+gpiod_direction_input(), or to use an IRQ number that didn't originally come
+from gpiod_to_irq(). gpiod_to_irq() is not allowed to sleep.
+
+Non-error values returned from gpiod_to_irq() can be passed to request_irq() or
+free_irq(). They will often be stored into IRQ resources for platform devices,
+by the board-specific initialization code. Note that IRQ trigger options are
+part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are system wakeup
+capabilities.
+
+
+Interacting With the Legacy GPIO Subsystem
+==========================================
+Many kernel subsystems still handle GPIOs using the legacy integer-based
+interface. Although it is strongly encouraged to upgrade them to the safer
+descriptor-based API, the following two functions allow you to convert a GPIO
+descriptor into the GPIO integer namespace and vice-versa:
+
+ int desc_to_gpio(const struct gpio_desc *desc)
+ struct gpio_desc *gpio_to_desc(unsigned gpio)
+
+The GPIO number returned by desc_to_gpio() can be safely used as long as the
+GPIO descriptor has not been freed. All the same, a GPIO number passed to
+gpio_to_desc() must have been properly acquired, and usage of the returned GPIO
+descriptor is only possible after the GPIO number has been released.
+
+Freeing a GPIO obtained by one API with the other API is forbidden and an
+unchecked error.
\ No newline at end of file
diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt
new file mode 100644
index 0000000..23f69e9
--- /dev/null
+++ b/Documentation/gpio/driver.txt
@@ -0,0 +1,75 @@
+GPIO Descriptor Driver Interface
+================================
+
+This document serves as a guide for GPIO chip drivers writers. Note that it
+describes the new descriptor-based interface. For a description of the
+deprecated integer-based GPIO interface please refer to gpio-legacy.txt.
+
+Each GPIO controller driver needs to include the following header, which defines
+the structures used to define a GPIO driver:
+
+ #include <linux/gpio/driver.h>
+
+
+Internal Representation of GPIOs
+================================
+
+Inside a GPIO driver, individual GPIOs are identified by their hardware number,
+which is a unique number between 0 and n, n being the number of GPIOs managed by
+the chip. This number is purely internal: the hardware number of a particular
+GPIO descriptor is never made visible outside of the driver.
+
+On top of this internal number, each GPIO also need to have a global number in
+the integer GPIO namespace so that it can be used with the legacy GPIO
+interface. Each chip must thus have a "base" number (which can be automatically
+assigned), and for each GPIO the global number will be (base + hardware number).
+Although the integer representation is considered deprecated, it still has many
+users and thus needs to be maintained.
+
+So for example one platform could use numbers 32-159 for GPIOs, with a
+controller defining 128 GPIOs at a "base" of 32 ; while another platform uses
+numbers 0..63 with one set of GPIO controllers, 64-79 with another type of GPIO
+controller, and on one particular board 80-95 with an FPGA. The numbers need not
+be contiguous; either of those platforms could also use numbers 2000-2063 to
+identify GPIOs in a bank of I2C GPIO expanders.
+
+
+Controller Drivers: gpio_chip
+=============================
+
+In the gpiolib framework each GPIO controller is packaged as a "struct
+gpio_chip" (see linux/gpio/driver.h for its complete definition) with members
+common to each controller of that type:
+
+ - methods to establish GPIO direction
+ - methods used to access GPIO values
+ - method to return the IRQ number associated to a given GPIO
+ - flag saying whether calls to its methods may sleep
+ - optional debugfs dump method (showing extra state like pullup config)
+ - optional base number (will be automatically assigned if omitted)
+ - label for diagnostics and GPIOs mapping using platform data
+
+The code implementing a gpio_chip should support multiple instances of the
+controller, possibly using the driver model. That code will configure each
+gpio_chip and issue gpiochip_add(). Removing a GPIO controller should be rare;
+use gpiochip_remove() when it is unavoidable.
+
+Most often a gpio_chip is part of an instance-specific structure with state not
+exposed by the GPIO interfaces, such as addressing, power management, and more.
+Chips such as codecs will have complex non-GPIO state.
+
+Any debugfs dump method should normally ignore signals which haven't been
+requested as GPIOs. They can use gpiochip_is_requested(), which returns either
+NULL or the label associated with that GPIO when it was requested.
+
+Locking IRQ usage
+-----------------
+Input GPIOs can be used as IRQ signals. When this happens, a driver is requested
+to mark the GPIO as being used as an IRQ:
+
+ int gpiod_lock_as_irq(struct gpio_desc *desc)
+
+This will prevent the use of non-irq related GPIO APIs until the GPIO IRQ lock
+is released:
+
+ void gpiod_unlock_as_irq(struct gpio_desc *desc)
diff --git a/Documentation/gpio/gpio-legacy.txt b/Documentation/gpio/gpio-legacy.txt
new file mode 100644
index 0000000..6f83fa9
--- /dev/null
+++ b/Documentation/gpio/gpio-legacy.txt
@@ -0,0 +1,775 @@
+GPIO Interfaces
+
+This provides an overview of GPIO access conventions on Linux.
+
+These calls use the gpio_* naming prefix. No other calls should use that
+prefix, or the related __gpio_* prefix.
+
+
+What is a GPIO?
+===============
+A "General Purpose Input/Output" (GPIO) is a flexible software-controlled
+digital signal. They are provided from many kinds of chip, and are familiar
+to Linux developers working with embedded and custom hardware. Each GPIO
+represents a bit connected to a particular pin, or "ball" on Ball Grid Array
+(BGA) packages. Board schematics show which external hardware connects to
+which GPIOs. Drivers can be written generically, so that board setup code
+passes such pin configuration data to drivers.
+
+System-on-Chip (SOC) processors heavily rely on GPIOs. In some cases, every
+non-dedicated pin can be configured as a GPIO; and most chips have at least
+several dozen of them. Programmable logic devices (like FPGAs) can easily
+provide GPIOs; multifunction chips like power managers, and audio codecs
+often have a few such pins to help with pin scarcity on SOCs; and there are
+also "GPIO Expander" chips that connect using the I2C or SPI serial busses.
+Most PC southbridges have a few dozen GPIO-capable pins (with only the BIOS
+firmware knowing how they're used).
+
+The exact capabilities of GPIOs vary between systems. Common options:
+
+ - Output values are writable (high=1, low=0). Some chips also have
+ options about how that value is driven, so that for example only one
+ value might be driven ... supporting "wire-OR" and similar schemes
+ for the other value (notably, "open drain" signaling).
+
+ - Input values are likewise readable (1, 0). Some chips support readback
+ of pins configured as "output", which is very useful in such "wire-OR"
+ cases (to support bidirectional signaling). GPIO controllers may have
+ input de-glitch/debounce logic, sometimes with software controls.
+
+ - Inputs can often be used as IRQ signals, often edge triggered but
+ sometimes level triggered. Such IRQs may be configurable as system
+ wakeup events, to wake the system from a low power state.
+
+ - Usually a GPIO will be configurable as either input or output, as needed
+ by different product boards; single direction ones exist too.
+
+ - Most GPIOs can be accessed while holding spinlocks, but those accessed
+ through a serial bus normally can't. Some systems support both types.
+
+On a given board each GPIO is used for one specific purpose like monitoring
+MMC/SD card insertion/removal, detecting card writeprotect status, driving
+a LED, configuring a transceiver, bitbanging a serial bus, poking a hardware
+watchdog, sensing a switch, and so on.
+
+
+GPIO conventions
+================
+Note that this is called a "convention" because you don't need to do it this
+way, and it's no crime if you don't. There **are** cases where portability
+is not the main issue; GPIOs are often used for the kind of board-specific
+glue logic that may even change between board revisions, and can't ever be
+used on a board that's wired differently. Only least-common-denominator
+functionality can be very portable. Other features are platform-specific,
+and that can be critical for glue logic.
+
+Plus, this doesn't require any implementation framework, just an interface.
+One platform might implement it as simple inline functions accessing chip
+registers; another might implement it by delegating through abstractions
+used for several very different kinds of GPIO controller. (There is some
+optional code supporting such an implementation strategy, described later
+in this document, but drivers acting as clients to the GPIO interface must
+not care how it's implemented.)
+
+That said, if the convention is supported on their platform, drivers should
+use it when possible. Platforms must select ARCH_REQUIRE_GPIOLIB or
+ARCH_WANT_OPTIONAL_GPIOLIB in their Kconfig. Drivers that can't work without
+standard GPIO calls should have Kconfig entries which depend on GPIOLIB. The
+GPIO calls are available, either as "real code" or as optimized-away stubs,
+when drivers use the include file:
+
+ #include <linux/gpio.h>
+
+If you stick to this convention then it'll be easier for other developers to
+see what your code is doing, and help maintain it.
+
+Note that these operations include I/O barriers on platforms which need to
+use them; drivers don't need to add them explicitly.
+
+
+Identifying GPIOs
+-----------------
+GPIOs are identified by unsigned integers in the range 0..MAX_INT. That
+reserves "negative" numbers for other purposes like marking signals as
+"not available on this board", or indicating faults. Code that doesn't
+touch the underlying hardware treats these integers as opaque cookies.
+
+Platforms define how they use those integers, and usually #define symbols
+for the GPIO lines so that board-specific setup code directly corresponds
+to the relevant schematics. In contrast, drivers should only use GPIO
+numbers passed to them from that setup code, using platform_data to hold
+board-specific pin configuration data (along with other board specific
+data they need). That avoids portability problems.
+
+So for example one platform uses numbers 32-159 for GPIOs; while another
+uses numbers 0..63 with one set of GPIO controllers, 64-79 with another
+type of GPIO controller, and on one particular board 80-95 with an FPGA.
+The numbers need not be contiguous; either of those platforms could also
+use numbers 2000-2063 to identify GPIOs in a bank of I2C GPIO expanders.
+
+If you want to initialize a structure with an invalid GPIO number, use
+some negative number (perhaps "-EINVAL"); that will never be valid. To
+test if such number from such a structure could reference a GPIO, you
+may use this predicate:
+
+ int gpio_is_valid(int number);
+
+A number that's not valid will be rejected by calls which may request
+or free GPIOs (see below). Other numbers may also be rejected; for
+example, a number might be valid but temporarily unused on a given board.
+
+Whether a platform supports multiple GPIO controllers is a platform-specific
+implementation issue, as are whether that support can leave "holes" in the space
+of GPIO numbers, and whether new controllers can be added at runtime. Such issues
+can affect things including whether adjacent GPIO numbers are both valid.
+
+Using GPIOs
+-----------
+The first thing a system should do with a GPIO is allocate it, using
+the gpio_request() call; see later.
+
+One of the next things to do with a GPIO, often in board setup code when
+setting up a platform_device using the GPIO, is mark its direction:
+
+ /* set as input or output, returning 0 or negative errno */
+ int gpio_direction_input(unsigned gpio);
+ int gpio_direction_output(unsigned gpio, int value);
+
+The return value is zero for success, else a negative errno. It should
+be checked, since the get/set calls don't have error returns and since
+misconfiguration is possible. You should normally issue these calls from
+a task context. However, for spinlock-safe GPIOs it's OK to use them
+before tasking is enabled, as part of early board setup.
+
+For output GPIOs, the value provided becomes the initial output value.
+This helps avoid signal glitching during system startup.
+
+For compatibility with legacy interfaces to GPIOs, setting the direction
+of a GPIO implicitly requests that GPIO (see below) if it has not been
+requested already. That compatibility is being removed from the optional
+gpiolib framework.
+
+Setting the direction can fail if the GPIO number is invalid, or when
+that particular GPIO can't be used in that mode. It's generally a bad
+idea to rely on boot firmware to have set the direction correctly, since
+it probably wasn't validated to do more than boot Linux. (Similarly,
+that board setup code probably needs to multiplex that pin as a GPIO,
+and configure pullups/pulldowns appropriately.)
+
+
+Spinlock-Safe GPIO access
+-------------------------
+Most GPIO controllers can be accessed with memory read/write instructions.
+Those don't need to sleep, and can safely be done from inside hard
+(nonthreaded) IRQ handlers and similar contexts.
+
+Use the following calls to access such GPIOs,
+for which gpio_cansleep() will always return false (see below):
+
+ /* GPIO INPUT: return zero or nonzero */
+ int gpio_get_value(unsigned gpio);
+
+ /* GPIO OUTPUT */
+ void gpio_set_value(unsigned gpio, int value);
+
+The values are boolean, zero for low, nonzero for high. When reading the
+value of an output pin, the value returned should be what's seen on the
+pin ... that won't always match the specified output value, because of
+issues including open-drain signaling and output latencies.
+
+The get/set calls have no error returns because "invalid GPIO" should have
+been reported earlier from gpio_direction_*(). However, note that not all
+platforms can read the value of output pins; those that can't should always
+return zero. Also, using these calls for GPIOs that can't safely be accessed
+without sleeping (see below) is an error.
+
+Platform-specific implementations are encouraged to optimize the two
+calls to access the GPIO value in cases where the GPIO number (and for
+output, value) are constant. It's normal for them to need only a couple
+of instructions in such cases (reading or writing a hardware register),
+and not to need spinlocks. Such optimized calls can make bitbanging
+applications a lot more efficient (in both space and time) than spending
+dozens of instructions on subroutine calls.
+
+
+GPIO access that may sleep
+--------------------------
+Some GPIO controllers must be accessed using message based busses like I2C
+or SPI. Commands to read or write those GPIO values require waiting to
+get to the head of a queue to transmit a command and get its response.
+This requires sleeping, which can't be done from inside IRQ handlers.
+
+Platforms that support this type of GPIO distinguish them from other GPIOs
+by returning nonzero from this call (which requires a valid GPIO number,
+which should have been previously allocated with gpio_request):
+
+ int gpio_cansleep(unsigned gpio);
+
+To access such GPIOs, a different set of accessors is defined:
+
+ /* GPIO INPUT: return zero or nonzero, might sleep */
+ int gpio_get_value_cansleep(unsigned gpio);
+
+ /* GPIO OUTPUT, might sleep */
+ void gpio_set_value_cansleep(unsigned gpio, int value);
+
+
+Accessing such GPIOs requires a context which may sleep, for example
+a threaded IRQ handler, and those accessors must be used instead of
+spinlock-safe accessors without the cansleep() name suffix.
+
+Other than the fact that these accessors might sleep, and will work
+on GPIOs that can't be accessed from hardIRQ handlers, these calls act
+the same as the spinlock-safe calls.
+
+ ** IN ADDITION ** calls to setup and configure such GPIOs must be made
+from contexts which may sleep, since they may need to access the GPIO
+controller chip too: (These setup calls are usually made from board
+setup or driver probe/teardown code, so this is an easy constraint.)
+
+ gpio_direction_input()
+ gpio_direction_output()
+ gpio_request()
+
+## gpio_request_one()
+## gpio_request_array()
+## gpio_free_array()
+
+ gpio_free()
+ gpio_set_debounce()
+
+
+
+Claiming and Releasing GPIOs
+----------------------------
+To help catch system configuration errors, two calls are defined.
+
+ /* request GPIO, returning 0 or negative errno.
+ * non-null labels may be useful for diagnostics.
+ */
+ int gpio_request(unsigned gpio, const char *label);
+
+ /* release previously-claimed GPIO */
+ void gpio_free(unsigned gpio);
+
+Passing invalid GPIO numbers to gpio_request() will fail, as will requesting
+GPIOs that have already been claimed with that call. The return value of
+gpio_request() must be checked. You should normally issue these calls from
+a task context. However, for spinlock-safe GPIOs it's OK to request GPIOs
+before tasking is enabled, as part of early board setup.
+
+These calls serve two basic purposes. One is marking the signals which
+are actually in use as GPIOs, for better diagnostics; systems may have
+several hundred potential GPIOs, but often only a dozen are used on any
+given board. Another is to catch conflicts, identifying errors when
+(a) two or more drivers wrongly think they have exclusive use of that
+signal, or (b) something wrongly believes it's safe to remove drivers
+needed to manage a signal that's in active use. That is, requesting a
+GPIO can serve as a kind of lock.
+
+Some platforms may also use knowledge about what GPIOs are active for
+power management, such as by powering down unused chip sectors and, more
+easily, gating off unused clocks.
+
+For GPIOs that use pins known to the pinctrl subsystem, that subsystem should
+be informed of their use; a gpiolib driver's .request() operation may call
+pinctrl_request_gpio(), and a gpiolib driver's .free() operation may call
+pinctrl_free_gpio(). The pinctrl subsystem allows a pinctrl_request_gpio()
+to succeed concurrently with a pin or pingroup being "owned" by a device for
+pin multiplexing.
+
+Any programming of pin multiplexing hardware that is needed to route the
+GPIO signal to the appropriate pin should occur within a GPIO driver's
+.direction_input() or .direction_output() operations, and occur after any
+setup of an output GPIO's value. This allows a glitch-free migration from a
+pin's special function to GPIO. This is sometimes required when using a GPIO
+to implement a workaround on signals typically driven by a non-GPIO HW block.
+
+Some platforms allow some or all GPIO signals to be routed to different pins.
+Similarly, other aspects of the GPIO or pin may need to be configured, such as
+pullup/pulldown. Platform software should arrange that any such details are
+configured prior to gpio_request() being called for those GPIOs, e.g. using
+the pinctrl subsystem's mapping table, so that GPIO users need not be aware
+of these details.
+
+Also note that it's your responsibility to have stopped using a GPIO
+before you free it.
+
+Considering in most cases GPIOs are actually configured right after they
+are claimed, three additional calls are defined:
+
+ /* request a single GPIO, with initial configuration specified by
+ * 'flags', identical to gpio_request() wrt other arguments and
+ * return value
+ */
+ int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
+
+ /* request multiple GPIOs in a single call
+ */
+ int gpio_request_array(struct gpio *array, size_t num);
+
+ /* release multiple GPIOs in a single call
+ */
+ void gpio_free_array(struct gpio *array, size_t num);
+
+where 'flags' is currently defined to specify the following properties:
+
+ * GPIOF_DIR_IN - to configure direction as input
+ * GPIOF_DIR_OUT - to configure direction as output
+
+ * GPIOF_INIT_LOW - as output, set initial level to LOW
+ * GPIOF_INIT_HIGH - as output, set initial level to HIGH
+ * GPIOF_OPEN_DRAIN - gpio pin is open drain type.
+ * GPIOF_OPEN_SOURCE - gpio pin is open source type.
+
+ * GPIOF_EXPORT_DIR_FIXED - export gpio to sysfs, keep direction
+ * GPIOF_EXPORT_DIR_CHANGEABLE - also export, allow changing direction
+
+since GPIOF_INIT_* are only valid when configured as output, so group valid
+combinations as:
+
+ * GPIOF_IN - configure as input
+ * GPIOF_OUT_INIT_LOW - configured as output, initial level LOW
+ * GPIOF_OUT_INIT_HIGH - configured as output, initial level HIGH
+
+When setting the flag as GPIOF_OPEN_DRAIN then it will assume that pins is
+open drain type. Such pins will not be driven to 1 in output mode. It is
+require to connect pull-up on such pins. By enabling this flag, gpio lib will
+make the direction to input when it is asked to set value of 1 in output mode
+to make the pin HIGH. The pin is make to LOW by driving value 0 in output mode.
+
+When setting the flag as GPIOF_OPEN_SOURCE then it will assume that pins is
+open source type. Such pins will not be driven to 0 in output mode. It is
+require to connect pull-down on such pin. By enabling this flag, gpio lib will
+make the direction to input when it is asked to set value of 0 in output mode
+to make the pin LOW. The pin is make to HIGH by driving value 1 in output mode.
+
+In the future, these flags can be extended to support more properties.
+
+Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
+introduced to encapsulate all three fields as:
+
+ struct gpio {
+ unsigned gpio;
+ unsigned long flags;
+ const char *label;
+ };
+
+A typical example of usage:
+
+ static struct gpio leds_gpios[] = {
+ { 32, GPIOF_OUT_INIT_HIGH, "Power LED" }, /* default to ON */
+ { 33, GPIOF_OUT_INIT_LOW, "Green LED" }, /* default to OFF */
+ { 34, GPIOF_OUT_INIT_LOW, "Red LED" }, /* default to OFF */
+ { 35, GPIOF_OUT_INIT_LOW, "Blue LED" }, /* default to OFF */
+ { ... },
+ };
+
+ err = gpio_request_one(31, GPIOF_IN, "Reset Button");
+ if (err)
+ ...
+
+ err = gpio_request_array(leds_gpios, ARRAY_SIZE(leds_gpios));
+ if (err)
+ ...
+
+ gpio_free_array(leds_gpios, ARRAY_SIZE(leds_gpios));
+
+
+GPIOs mapped to IRQs
+--------------------
+GPIO numbers are unsigned integers; so are IRQ numbers. These make up
+two logically distinct namespaces (GPIO 0 need not use IRQ 0). You can
+map between them using calls like:
+
+ /* map GPIO numbers to IRQ numbers */
+ int gpio_to_irq(unsigned gpio);
+
+ /* map IRQ numbers to GPIO numbers (avoid using this) */
+ int irq_to_gpio(unsigned irq);
+
+Those return either the corresponding number in the other namespace, or
+else a negative errno code if the mapping can't be done. (For example,
+some GPIOs can't be used as IRQs.) It is an unchecked error to use a GPIO
+number that wasn't set up as an input using gpio_direction_input(), or
+to use an IRQ number that didn't originally come from gpio_to_irq().
+
+These two mapping calls are expected to cost on the order of a single
+addition or subtraction. They're not allowed to sleep.
+
+Non-error values returned from gpio_to_irq() can be passed to request_irq()
+or free_irq(). They will often be stored into IRQ resources for platform
+devices, by the board-specific initialization code. Note that IRQ trigger
+options are part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are
+system wakeup capabilities.
+
+Non-error values returned from irq_to_gpio() would most commonly be used
+with gpio_get_value(), for example to initialize or update driver state
+when the IRQ is edge-triggered. Note that some platforms don't support
+this reverse mapping, so you should avoid using it.
+
+
+Emulating Open Drain Signals
+----------------------------
+Sometimes shared signals need to use "open drain" signaling, where only the
+low signal level is actually driven. (That term applies to CMOS transistors;
+"open collector" is used for TTL.) A pullup resistor causes the high signal
+level. This is sometimes called a "wire-AND"; or more practically, from the
+negative logic (low=true) perspective this is a "wire-OR".
+
+One common example of an open drain signal is a shared active-low IRQ line.
+Also, bidirectional data bus signals sometimes use open drain signals.
+
+Some GPIO controllers directly support open drain outputs; many don't. When
+you need open drain signaling but your hardware doesn't directly support it,
+there's a common idiom you can use to emulate it with any GPIO pin that can
+be used as either an input or an output:
+
+ LOW: gpio_direction_output(gpio, 0) ... this drives the signal
+ and overrides the pullup.
+
+ HIGH: gpio_direction_input(gpio) ... this turns off the output,
+ so the pullup (or some other device) controls the signal.
+
+If you are "driving" the signal high but gpio_get_value(gpio) reports a low
+value (after the appropriate rise time passes), you know some other component
+is driving the shared signal low. That's not necessarily an error. As one
+common example, that's how I2C clocks are stretched: a slave that needs a
+slower clock delays the rising edge of SCK, and the I2C master adjusts its
+signaling rate accordingly.
+
+
+GPIO controllers and the pinctrl subsystem
+------------------------------------------
+
+A GPIO controller on a SOC might be tightly coupled with the pinctrl
+subsystem, in the sense that the pins can be used by other functions
+together with an optional gpio feature. We have already covered the
+case where e.g. a GPIO controller need to reserve a pin or set the
+direction of a pin by calling any of:
+
+pinctrl_request_gpio()
+pinctrl_free_gpio()
+pinctrl_gpio_direction_input()
+pinctrl_gpio_direction_output()
+
+But how does the pin control subsystem cross-correlate the GPIO
+numbers (which are a global business) to a certain pin on a certain
+pin controller?
+
+This is done by registering "ranges" of pins, which are essentially
+cross-reference tables. These are described in
+Documentation/pinctrl.txt
+
+While the pin allocation is totally managed by the pinctrl subsystem,
+gpio (under gpiolib) is still maintained by gpio drivers. It may happen
+that different pin ranges in a SoC is managed by different gpio drivers.
+
+This makes it logical to let gpio drivers announce their pin ranges to
+the pin ctrl subsystem before it will call 'pinctrl_request_gpio' in order
+to request the corresponding pin to be prepared by the pinctrl subsystem
+before any gpio usage.
+
+For this, the gpio controller can register its pin range with pinctrl
+subsystem. There are two ways of doing it currently: with or without DT.
+
+For with DT support refer to Documentation/devicetree/bindings/gpio/gpio.txt.
+
+For non-DT support, user can call gpiochip_add_pin_range() with appropriate
+parameters to register a range of gpio pins with a pinctrl driver. For this
+exact name string of pinctrl device has to be passed as one of the
+argument to this routine.
+
+
+What do these conventions omit?
+===============================
+One of the biggest things these conventions omit is pin multiplexing, since
+this is highly chip-specific and nonportable. One platform might not need
+explicit multiplexing; another might have just two options for use of any
+given pin; another might have eight options per pin; another might be able
+to route a given GPIO to any one of several pins. (Yes, those examples all
+come from systems that run Linux today.)
+
+Related to multiplexing is configuration and enabling of the pullups or
+pulldowns integrated on some platforms. Not all platforms support them,
+or support them in the same way; and any given board might use external
+pullups (or pulldowns) so that the on-chip ones should not be used.
+(When a circuit needs 5 kOhm, on-chip 100 kOhm resistors won't do.)
+Likewise drive strength (2 mA vs 20 mA) and voltage (1.8V vs 3.3V) is a
+platform-specific issue, as are models like (not) having a one-to-one
+correspondence between configurable pins and GPIOs.
+
+There are other system-specific mechanisms that are not specified here,
+like the aforementioned options for input de-glitching and wire-OR output.
+Hardware may support reading or writing GPIOs in gangs, but that's usually
+configuration dependent: for GPIOs sharing the same bank. (GPIOs are
+commonly grouped in banks of 16 or 32, with a given SOC having several such
+banks.) Some systems can trigger IRQs from output GPIOs, or read values
+from pins not managed as GPIOs. Code relying on such mechanisms will
+necessarily be nonportable.
+
+Dynamic definition of GPIOs is not currently standard; for example, as
+a side effect of configuring an add-on board with some GPIO expanders.
+
+
+GPIO implementor's framework (OPTIONAL)
+=======================================
+As noted earlier, there is an optional implementation framework making it
+easier for platforms to support different kinds of GPIO controller using
+the same programming interface. This framework is called "gpiolib".
+
+As a debugging aid, if debugfs is available a /sys/kernel/debug/gpio file
+will be found there. That will list all the controllers registered through
+this framework, and the state of the GPIOs currently in use.
+
+
+Controller Drivers: gpio_chip
+-----------------------------
+In this framework each GPIO controller is packaged as a "struct gpio_chip"
+with information common to each controller of that type:
+
+ - methods to establish GPIO direction
+ - methods used to access GPIO values
+ - flag saying whether calls to its methods may sleep
+ - optional debugfs dump method (showing extra state like pullup config)
+ - label for diagnostics
+
+There is also per-instance data, which may come from device.platform_data:
+the number of its first GPIO, and how many GPIOs it exposes.
+
+The code implementing a gpio_chip should support multiple instances of the
+controller, possibly using the driver model. That code will configure each
+gpio_chip and issue gpiochip_add(). Removing a GPIO controller should be
+rare; use gpiochip_remove() when it is unavoidable.
+
+Most often a gpio_chip is part of an instance-specific structure with state
+not exposed by the GPIO interfaces, such as addressing, power management,
+and more. Chips such as codecs will have complex non-GPIO state.
+
+Any debugfs dump method should normally ignore signals which haven't been
+requested as GPIOs. They can use gpiochip_is_requested(), which returns
+either NULL or the label associated with that GPIO when it was requested.
+
+
+Platform Support
+----------------
+To support this framework, a platform's Kconfig will "select" either
+ARCH_REQUIRE_GPIOLIB or ARCH_WANT_OPTIONAL_GPIOLIB
+and arrange that its <asm/gpio.h> includes <asm-generic/gpio.h> and defines
+three functions: gpio_get_value(), gpio_set_value(), and gpio_cansleep().
+
+It may also provide a custom value for ARCH_NR_GPIOS, so that it better
+reflects the number of GPIOs in actual use on that platform, without
+wasting static table space. (It should count both built-in/SoC GPIOs and
+also ones on GPIO expanders.
+
+ARCH_REQUIRE_GPIOLIB means that the gpiolib code will always get compiled
+into the kernel on that architecture.
+
+ARCH_WANT_OPTIONAL_GPIOLIB means the gpiolib code defaults to off and the user
+can enable it and build it into the kernel optionally.
+
+If neither of these options are selected, the platform does not support
+GPIOs through GPIO-lib and the code cannot be enabled by the user.
+
+Trivial implementations of those functions can directly use framework
+code, which always dispatches through the gpio_chip:
+
+ #define gpio_get_value __gpio_get_value
+ #define gpio_set_value __gpio_set_value
+ #define gpio_cansleep __gpio_cansleep
+
+Fancier implementations could instead define those as inline functions with
+logic optimizing access to specific SOC-based GPIOs. For example, if the
+referenced GPIO is the constant "12", getting or setting its value could
+cost as little as two or three instructions, never sleeping. When such an
+optimization is not possible those calls must delegate to the framework
+code, costing at least a few dozen instructions. For bitbanged I/O, such
+instruction savings can be significant.
+
+For SOCs, platform-specific code defines and registers gpio_chip instances
+for each bank of on-chip GPIOs. Those GPIOs should be numbered/labeled to
+match chip vendor documentation, and directly match board schematics. They
+may well start at zero and go up to a platform-specific limit. Such GPIOs
+are normally integrated into platform initialization to make them always be
+available, from arch_initcall() or earlier; they can often serve as IRQs.
+
+
+Board Support
+-------------
+For external GPIO controllers -- such as I2C or SPI expanders, ASICs, multi
+function devices, FPGAs or CPLDs -- most often board-specific code handles
+registering controller devices and ensures that their drivers know what GPIO
+numbers to use with gpiochip_add(). Their numbers often start right after
+platform-specific GPIOs.
+
+For example, board setup code could create structures identifying the range
+of GPIOs that chip will expose, and passes them to each GPIO expander chip
+using platform_data. Then the chip driver's probe() routine could pass that
+data to gpiochip_add().
+
+Initialization order can be important. For example, when a device relies on
+an I2C-based GPIO, its probe() routine should only be called after that GPIO
+becomes available. That may mean the device should not be registered until
+calls for that GPIO can work. One way to address such dependencies is for
+such gpio_chip controllers to provide setup() and teardown() callbacks to
+board specific code; those board specific callbacks would register devices
+once all the necessary resources are available, and remove them later when
+the GPIO controller device becomes unavailable.
+
+
+Sysfs Interface for Userspace (OPTIONAL)
+========================================
+Platforms which use the "gpiolib" implementors framework may choose to
+configure a sysfs user interface to GPIOs. This is different from the
+debugfs interface, since it provides control over GPIO direction and
+value instead of just showing a gpio state summary. Plus, it could be
+present on production systems without debugging support.
+
+Given appropriate hardware documentation for the system, userspace could
+know for example that GPIO #23 controls the write protect line used to
+protect boot loader segments in flash memory. System upgrade procedures
+may need to temporarily remove that protection, first importing a GPIO,
+then changing its output state, then updating the code before re-enabling
+the write protection. In normal use, GPIO #23 would never be touched,
+and the kernel would have no need to know about it.
+
+Again depending on appropriate hardware documentation, on some systems
+userspace GPIO can be used to determine system configuration data that
+standard kernels won't know about. And for some tasks, simple userspace
+GPIO drivers could be all that the system really needs.
+
+Note that standard kernel drivers exist for common "LEDs and Buttons"
+GPIO tasks: "leds-gpio" and "gpio_keys", respectively. Use those
+instead of talking directly to the GPIOs; they integrate with kernel
+frameworks better than your userspace code could.
+
+
+Paths in Sysfs
+--------------
+There are three kinds of entry in /sys/class/gpio:
+
+ - Control interfaces used to get userspace control over GPIOs;
+
+ - GPIOs themselves; and
+
+ - GPIO controllers ("gpio_chip" instances).
+
+That's in addition to standard files including the "device" symlink.
+
+The control interfaces are write-only:
+
+ /sys/class/gpio/
+
+ "export" ... Userspace may ask the kernel to export control of
+ a GPIO to userspace by writing its number to this file.
+
+ Example: "echo 19 > export" will create a "gpio19" node
+ for GPIO #19, if that's not requested by kernel code.
+
+ "unexport" ... Reverses the effect of exporting to userspace.
+
+ Example: "echo 19 > unexport" will remove a "gpio19"
+ node exported using the "export" file.
+
+GPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42)
+and have the following read/write attributes:
+
+ /sys/class/gpio/gpioN/
+
+ "direction" ... reads as either "in" or "out". This value may
+ normally be written. Writing as "out" defaults to
+ initializing the value as low. To ensure glitch free
+ operation, values "low" and "high" may be written to
+ configure the GPIO as an output with that initial value.
+
+ Note that this attribute *will not exist* if the kernel
+ doesn't support changing the direction of a GPIO, or
+ it was exported by kernel code that didn't explicitly
+ allow userspace to reconfigure this GPIO's direction.
+
+ "value" ... reads as either 0 (low) or 1 (high). If the GPIO
+ is configured as an output, this value may be written;
+ any nonzero value is treated as high.
+
+ If the pin can be configured as interrupt-generating interrupt
+ and if it has been configured to generate interrupts (see the
+ description of "edge"), you can poll(2) on that file and
+ poll(2) will return whenever the interrupt was triggered. If
+ you use poll(2), set the events POLLPRI and POLLERR. If you
+ use select(2), set the file descriptor in exceptfds. After
+ poll(2) returns, either lseek(2) to the beginning of the sysfs
+ file and read the new value or close the file and re-open it
+ to read the value.
+
+ "edge" ... reads as either "none", "rising", "falling", or
+ "both". Write these strings to select the signal edge(s)
+ that will make poll(2) on the "value" file return.
+
+ This file exists only if the pin can be configured as an
+ interrupt generating input pin.
+
+ "active_low" ... reads as either 0 (false) or 1 (true). Write
+ any nonzero value to invert the value attribute both
+ for reading and writing. Existing and subsequent
+ poll(2) support configuration via the edge attribute
+ for "rising" and "falling" edges will follow this
+ setting.
+
+GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
+controller implementing GPIOs starting at #42) and have the following
+read-only attributes:
+
+ /sys/class/gpio/gpiochipN/
+
+ "base" ... same as N, the first GPIO managed by this chip
+
+ "label" ... provided for diagnostics (not always unique)
+
+ "ngpio" ... how many GPIOs this manges (N to N + ngpio - 1)
+
+Board documentation should in most cases cover what GPIOs are used for
+what purposes. However, those numbers are not always stable; GPIOs on
+a daughtercard might be different depending on the base board being used,
+or other cards in the stack. In such cases, you may need to use the
+gpiochip nodes (possibly in conjunction with schematics) to determine
+the correct GPIO number to use for a given signal.
+
+
+Exporting from Kernel code
+--------------------------
+Kernel code can explicitly manage exports of GPIOs which have already been
+requested using gpio_request():
+
+ /* export the GPIO to userspace */
+ int gpio_export(unsigned gpio, bool direction_may_change);
+
+ /* reverse gpio_export() */
+ void gpio_unexport();
+
+ /* create a sysfs link to an exported GPIO node */
+ int gpio_export_link(struct device *dev, const char *name,
+ unsigned gpio)
+
+ /* change the polarity of a GPIO node in sysfs */
+ int gpio_sysfs_set_active_low(unsigned gpio, int value);
+
+After a kernel driver requests a GPIO, it may only be made available in
+the sysfs interface by gpio_export(). The driver can control whether the
+signal direction may change. This helps drivers prevent userspace code
+from accidentally clobbering important system state.
+
+This explicit exporting can help with debugging (by making some kinds
+of experiments easier), or can provide an always-there interface that's
+suitable for documenting as part of a board support package.
+
+After the GPIO has been exported, gpio_export_link() allows creating
+symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
+use this to provide the interface under their own device in sysfs with
+a descriptive name.
+
+Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity
+differences between boards from user space. This only affects the
+sysfs interface. Polarity change can be done both before and after
+gpio_export(), and previously enabled poll(2) support for either
+rising or falling edge will be reconfigured to follow this setting.
diff --git a/Documentation/gpio/gpio.txt b/Documentation/gpio/gpio.txt
new file mode 100644
index 0000000..7ee850b
--- /dev/null
+++ b/Documentation/gpio/gpio.txt
@@ -0,0 +1,119 @@
+GPIO Interfaces
+===============
+
+The documents in this directory give detailed instructions on how to access
+GPIOs in drivers, and how to write a driver for a device that provides GPIOs
+itself.
+
+Due to the history of GPIO interfaces in the kernel, there are two different
+ways to obtain and use GPIOs:
+
+ - The descriptor-based interface is the preferred way to manipulate GPIOs,
+and is described by all the files in this directory excepted gpio-legacy.txt.
+ - The legacy integer-based interface which is considered deprecated (but still
+usable for compatibility reasons) is documented in gpio-legacy.txt.
+
+The remainder of this document applies to the new descriptor-based interface.
+gpio-legacy.txt contains the same information applied to the legacy
+integer-based interface.
+
+
+What is a GPIO?
+===============
+
+A "General Purpose Input/Output" (GPIO) is a flexible software-controlled
+digital signal. They are provided from many kinds of chip, and are familiar
+to Linux developers working with embedded and custom hardware. Each GPIO
+represents a bit connected to a particular pin, or "ball" on Ball Grid Array
+(BGA) packages. Board schematics show which external hardware connects to
+which GPIOs. Drivers can be written generically, so that board setup code
+passes such pin configuration data to drivers.
+
+System-on-Chip (SOC) processors heavily rely on GPIOs. In some cases, every
+non-dedicated pin can be configured as a GPIO; and most chips have at least
+several dozen of them. Programmable logic devices (like FPGAs) can easily
+provide GPIOs; multifunction chips like power managers, and audio codecs
+often have a few such pins to help with pin scarcity on SOCs; and there are
+also "GPIO Expander" chips that connect using the I2C or SPI serial buses.
+Most PC southbridges have a few dozen GPIO-capable pins (with only the BIOS
+firmware knowing how they're used).
+
+The exact capabilities of GPIOs vary between systems. Common options:
+
+ - Output values are writable (high=1, low=0). Some chips also have
+ options about how that value is driven, so that for example only one
+ value might be driven, supporting "wire-OR" and similar schemes for the
+ other value (notably, "open drain" signaling).
+
+ - Input values are likewise readable (1, 0). Some chips support readback
+ of pins configured as "output", which is very useful in such "wire-OR"
+ cases (to support bidirectional signaling). GPIO controllers may have
+ input de-glitch/debounce logic, sometimes with software controls.
+
+ - Inputs can often be used as IRQ signals, often edge triggered but
+ sometimes level triggered. Such IRQs may be configurable as system
+ wakeup events, to wake the system from a low power state.
+
+ - Usually a GPIO will be configurable as either input or output, as needed
+ by different product boards; single direction ones exist too.
+
+ - Most GPIOs can be accessed while holding spinlocks, but those accessed
+ through a serial bus normally can't. Some systems support both types.
+
+On a given board each GPIO is used for one specific purpose like monitoring
+MMC/SD card insertion/removal, detecting card write-protect status, driving
+a LED, configuring a transceiver, bit-banging a serial bus, poking a hardware
+watchdog, sensing a switch, and so on.
+
+
+Common GPIO Properties
+======================
+
+These properties are met through all the other documents of the GPIO interface
+and it is useful to understand them, especially if you need to define GPIO
+mappings.
+
+Active-High and Active-Low
+--------------------------
+It is natural to assume that a GPIO is "active" when its output signal is 1
+("high"), and inactive when it is 0 ("low"). However in practice the signal of a
+GPIO may be inverted before is reaches its destination, or a device could decide
+to have different conventions about what "active" means. Such decisions should
+be transparent to device drivers, therefore it is possible to define a GPIO as
+being either active-high ("1" means "active", the default) or active-low ("0"
+means "active") so that drivers only need to worry about the logical signal and
+not about what happens at the line level.
+
+Open Drain and Open Source
+--------------------------
+Sometimes shared signals need to use "open drain" (where only the low signal
+level is actually driven), or "open source" (where only the high signal level is
+driven) signaling. That term applies to CMOS transistors; "open collector" is
+used for TTL. A pullup or pulldown resistor causes the high or low signal level.
+This is sometimes called a "wire-AND"; or more practically, from the negative
+logic (low=true) perspective this is a "wire-OR".
+
+One common example of an open drain signal is a shared active-low IRQ line.
+Also, bidirectional data bus signals sometimes use open drain signals.
+
+Some GPIO controllers directly support open drain and open source outputs; many
+don't. When you need open drain signaling but your hardware doesn't directly
+support it, there's a common idiom you can use to emulate it with any GPIO pin
+that can be used as either an input or an output:
+
+ LOW: gpiod_direction_output(gpio, 0) ... this drives the signal and overrides
+ the pullup.
+
+ HIGH: gpiod_direction_input(gpio) ... this turns off the output, so the pullup
+ (or some other device) controls the signal.
+
+The same logic can be applied to emulate open source signaling, by driving the
+high signal and configuring the GPIO as input for low. This open drain/open
+source emulation can be handled transparently by the GPIO framework.
+
+If you are "driving" the signal high but gpiod_get_value(gpio) reports a low
+value (after the appropriate rise time passes), you know some other component is
+driving the shared signal low. That's not necessarily an error. As one common
+example, that's how I2C clocks are stretched: a slave that needs a slower clock
+delays the rising edge of SCK, and the I2C master adjusts its signaling rate
+accordingly.
diff --git a/Documentation/gpio/sysfs.txt b/Documentation/gpio/sysfs.txt
new file mode 100644
index 0000000..d8d18a7
--- /dev/null
+++ b/Documentation/gpio/sysfs.txt
@@ -0,0 +1,155 @@
+GPIO Sysfs Interface for Userspace
+==================================
+
+Platforms which use the "gpiolib" implementors framework may choose to
+configure a sysfs user interface to GPIOs. This is different from the
+debugfs interface, since it provides control over GPIO direction and
+value instead of just showing a gpio state summary. Plus, it could be
+present on production systems without debugging support.
+
+Given appropriate hardware documentation for the system, userspace could
+know for example that GPIO #23 controls the write protect line used to
+protect boot loader segments in flash memory. System upgrade procedures
+may need to temporarily remove that protection, first importing a GPIO,
+then changing its output state, then updating the code before re-enabling
+the write protection. In normal use, GPIO #23 would never be touched,
+and the kernel would have no need to know about it.
+
+Again depending on appropriate hardware documentation, on some systems
+userspace GPIO can be used to determine system configuration data that
+standard kernels won't know about. And for some tasks, simple userspace
+GPIO drivers could be all that the system really needs.
+
+Note that standard kernel drivers exist for common "LEDs and Buttons"
+GPIO tasks: "leds-gpio" and "gpio_keys", respectively. Use those
+instead of talking directly to the GPIOs; they integrate with kernel
+frameworks better than your userspace code could.
+
+
+Paths in Sysfs
+--------------
+There are three kinds of entry in /sys/class/gpio:
+
+ - Control interfaces used to get userspace control over GPIOs;
+
+ - GPIOs themselves; and
+
+ - GPIO controllers ("gpio_chip" instances).
+
+That's in addition to standard files including the "device" symlink.
+
+The control interfaces are write-only:
+
+ /sys/class/gpio/
+
+ "export" ... Userspace may ask the kernel to export control of
+ a GPIO to userspace by writing its number to this file.
+
+ Example: "echo 19 > export" will create a "gpio19" node
+ for GPIO #19, if that's not requested by kernel code.
+
+ "unexport" ... Reverses the effect of exporting to userspace.
+
+ Example: "echo 19 > unexport" will remove a "gpio19"
+ node exported using the "export" file.
+
+GPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42)
+and have the following read/write attributes:
+
+ /sys/class/gpio/gpioN/
+
+ "direction" ... reads as either "in" or "out". This value may
+ normally be written. Writing as "out" defaults to
+ initializing the value as low. To ensure glitch free
+ operation, values "low" and "high" may be written to
+ configure the GPIO as an output with that initial value.
+
+ Note that this attribute *will not exist* if the kernel
+ doesn't support changing the direction of a GPIO, or
+ it was exported by kernel code that didn't explicitly
+ allow userspace to reconfigure this GPIO's direction.
+
+ "value" ... reads as either 0 (low) or 1 (high). If the GPIO
+ is configured as an output, this value may be written;
+ any nonzero value is treated as high.
+
+ If the pin can be configured as interrupt-generating interrupt
+ and if it has been configured to generate interrupts (see the
+ description of "edge"), you can poll(2) on that file and
+ poll(2) will return whenever the interrupt was triggered. If
+ you use poll(2), set the events POLLPRI and POLLERR. If you
+ use select(2), set the file descriptor in exceptfds. After
+ poll(2) returns, either lseek(2) to the beginning of the sysfs
+ file and read the new value or close the file and re-open it
+ to read the value.
+
+ "edge" ... reads as either "none", "rising", "falling", or
+ "both". Write these strings to select the signal edge(s)
+ that will make poll(2) on the "value" file return.
+
+ This file exists only if the pin can be configured as an
+ interrupt generating input pin.
+
+ "active_low" ... reads as either 0 (false) or 1 (true). Write
+ any nonzero value to invert the value attribute both
+ for reading and writing. Existing and subsequent
+ poll(2) support configuration via the edge attribute
+ for "rising" and "falling" edges will follow this
+ setting.
+
+GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
+controller implementing GPIOs starting at #42) and have the following
+read-only attributes:
+
+ /sys/class/gpio/gpiochipN/
+
+ "base" ... same as N, the first GPIO managed by this chip
+
+ "label" ... provided for diagnostics (not always unique)
+
+ "ngpio" ... how many GPIOs this manges (N to N + ngpio - 1)
+
+Board documentation should in most cases cover what GPIOs are used for
+what purposes. However, those numbers are not always stable; GPIOs on
+a daughtercard might be different depending on the base board being used,
+or other cards in the stack. In such cases, you may need to use the
+gpiochip nodes (possibly in conjunction with schematics) to determine
+the correct GPIO number to use for a given signal.
+
+
+Exporting from Kernel code
+--------------------------
+Kernel code can explicitly manage exports of GPIOs which have already been
+requested using gpio_request():
+
+ /* export the GPIO to userspace */
+ int gpiod_export(struct gpio_desc *desc, bool direction_may_change);
+
+ /* reverse gpio_export() */
+ void gpiod_unexport(struct gpio_desc *desc);
+
+ /* create a sysfs link to an exported GPIO node */
+ int gpiod_export_link(struct device *dev, const char *name,
+ struct gpio_desc *desc);
+
+ /* change the polarity of a GPIO node in sysfs */
+ int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value);
+
+After a kernel driver requests a GPIO, it may only be made available in
+the sysfs interface by gpiod_export(). The driver can control whether the
+signal direction may change. This helps drivers prevent userspace code
+from accidentally clobbering important system state.
+
+This explicit exporting can help with debugging (by making some kinds
+of experiments easier), or can provide an always-there interface that's
+suitable for documenting as part of a board support package.
+
+After the GPIO has been exported, gpiod_export_link() allows creating
+symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
+use this to provide the interface under their own device in sysfs with
+a descriptive name.
+
+Drivers can use gpiod_sysfs_set_active_low() to hide GPIO line polarity
+differences between boards from user space. Polarity change can be done both
+before and after gpiod_export(), and previously enabled poll(2) support for
+either rising or falling edge will be reconfigured to follow this setting.
--
1.8.4.2
--
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Please read the FAQ at http://www.tux.org/lkml/
==============================================================================
TOPIC: gpiolib: fix find_chip_by_name()
http://groups.google.com/group/linux.kernel/t/e5465eaabcc515a0?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:50 am
From: Alexandre Courbot
find_chip_by_name() was incorrectly implemented by using
gpio_lookup_list instead of gpiod_chips to iterate through all the
registered GPIO controllers. This patch reimplements it by using
gpiochip_find() with a custom search function, which simplifies the code
on top of fixing the mistake.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
drivers/gpio/gpiolib.c | 29 ++++++++++++-----------------
1 file changed, 12 insertions(+), 17 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9f3326b..63bbf5b 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1307,6 +1307,18 @@ struct gpio_chip *gpiochip_find(void *data,
}
EXPORT_SYMBOL_GPL(gpiochip_find);
+static int gpiochip_match_name(struct gpio_chip *chip, void *data)
+{
+ const char *name = data;
+
+ return !strcmp(chip->label, name);
+}
+
+static struct gpio_chip *find_chip_by_name(const char *name)
+{
+ return gpiochip_find((void *)name, gpiochip_match_name);
+}
+
#ifdef CONFIG_PINCTRL
/**
@@ -2212,23 +2224,6 @@ void gpiod_add_table(struct gpiod_lookup *table, size_t size)
mutex_unlock(&gpio_lookup_lock);
}
-/*
- * Caller must have a acquired gpio_lookup_lock
- */
-static struct gpio_chip *find_chip_by_name(const char *name)
-{
- struct gpio_chip *chip = NULL;
-
- list_for_each_entry(chip, &gpio_lookup_list, list) {
- if (chip->label == NULL)
- continue;
- if (!strcmp(chip->label, name))
- break;
- }
-
- return chip;
-}
-
#ifdef CONFIG_OF
static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
unsigned int idx, unsigned long *flags)
--
1.8.4.2
--
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Please read the FAQ at http://www.tux.org/lkml/
==============================================================================
TOPIC: gpiolib: use dedicated flags for GPIO properties
http://groups.google.com/group/linux.kernel/t/076bd57cb3ab2c53?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 16 2013 4:50 am
From: Alexandre Courbot
GPIO mapping properties were defined using the GPIOF_* flags, which are
declared in linux/gpio.h. This file is not included when using the
GPIO descriptor interface.
This patch declares the flags that can be used as GPIO mappings
properties in linux/gpio/driver.h, and uses them in gpiolib, so that no
deprecated declarations are used by the GPIO descriptor interface.
This patch also allows GPIO_OPEN_DRAIN and GPIO_OPEN_SOURCE to be
specified as GPIO mapping properties.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
--
The new GPIO interface documentation already uses these new declarations.
It would be nice to have this merged in a 3.13-rc since it is necessary
to properly declare GPIO mappings as platform data.
---
drivers/gpio/gpiolib.c | 22 +++++++++++++++-------
include/linux/gpio/driver.h | 11 +++++++++--
2 files changed, 24 insertions(+), 9 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 63bbf5b..be5dbc2 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -13,6 +13,7 @@
#include <linux/acpi_gpio.h>
#include <linux/idr.h>
#include <linux/slab.h>
+#include <linux/gpio/driver.h>
#define CREATE_TRACE_POINTS
#include <trace/events/gpio.h>
@@ -2226,7 +2227,8 @@ void gpiod_add_table(struct gpiod_lookup *table, size_t size)
#ifdef CONFIG_OF
static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
- unsigned int idx, unsigned long *flags)
+ unsigned int idx,
+ enum gpio_lookup_flags *flags)
{
char prop_name[32]; /* 32 is max size of property name */
enum of_gpio_flags of_flags;
@@ -2244,7 +2246,7 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
return desc;
if (of_flags & OF_GPIO_ACTIVE_LOW)
- *flags |= GPIOF_ACTIVE_LOW;
+ *flags |= GPIO_ACTIVE_LOW;
return desc;
}
@@ -2257,7 +2259,8 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
posted by twitter @ 11:53 AM
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