linux.kernel - 26 new messages in 5 topics - digest

linux.kernel
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Today's topics:

* USB mass storage and ARM cache coherency - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/68938cdf1fa061a9?hl=en
* tty: Fix up char drivers request_room usage - 8 messages, 1 author
http://groups.google.com/group/linux.kernel/t/08c1b2b68bc4f84b?hl=en
* kobject: Constify struct kset_uevent_ops - 15 messages, 1 author
http://groups.google.com/group/linux.kernel/t/63818dfc875730b2?hl=en
* [PATCH -next] scsi: RAID_ATTRS depends on SCSI - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/71c7bcb275f3e323?hl=en
* pktcdvd: improve BKL and compat_ioctl.c usage - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/34267fa09ddc834e?hl=en

==============================================================================
TOPIC: USB mass storage and ARM cache coherency
http://groups.google.com/group/linux.kernel/t/68938cdf1fa061a9?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, Mar 2 2010 3:40 pm
From: Benjamin Herrenschmidt

On Tue, 2010-03-02 at 17:05 +0000, Catalin Marinas wrote:

> The viable solutions so far:
>
> 1. Implement a PIO mapping API similar to the DMA API which takes
> care of the D-cache flushing. This means that PIO drivers would
> need to be modified to use an API like pio_kmap()/pio_kunmap()
> before writing to a page cache page.
> 2. Invert the meaning of PG_arch_1 to denote a clean page. This
> means that by default newly allocated page cache pages are
> considered dirty and even if there isn't a call to
> flush_dcache_page(), update_mmu_cache() would flush the D-cache.
> This is the PowerPC approach.

I don't see the point of a "PIO" API. I would thus vote for 2 :-) Note
that flushing the D-cache isn't enough, you also need to invalidate the
I-cache as we discussed earlier, though you mostly get away if you don't
by luck.

There's also a question as to whether clearing PG_arch_1 is
flush_dcache_page() is really necessary or not.

> Option 2 above looks pretty appealing to me since it can be done in the
> ARM code exclusively. I've done some tests and it indeed solves the
> cache coherency with a rootfs on a USB stick. As Russell suggested, it
> can be optimised to mark a page as clean when the DMA API is involved to
> avoid duplicate flushing.

That wouldn't solve the need for invalidating the I-cache... Unless we
use another bit.

> It was also suggested to add a PG_arch_2 flag which would keep track of
> the I-cache status as well.
>
> I can post a proposal to modify the cachetlb.txt document to reflect the
> issues we currently have on ARM.

Cheers,
Ben.

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==============================================================================
TOPIC: tty: Fix up char drivers request_room usage
http://groups.google.com/group/linux.kernel/t/08c1b2b68bc4f84b?hl=en
==============================================================================

== 1 of 8 ==
Date: Tues, Mar 2 2010 3:40 pm
From: Greg Kroah-Hartman

From: Alan Cox <alan@linux.intel.com>

We can't change them all but quite a few misuse it.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/char/nozomi.c | 2 --
drivers/char/serial167.c | 3 +--
drivers/char/specialix.c | 2 --
drivers/serial/icom.c | 1 -
drivers/serial/ioc3_serial.c | 3 +--
5 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/char/nozomi.c b/drivers/char/nozomi.c
index 584910f..a3f32a1 100644
--- a/drivers/char/nozomi.c
+++ b/drivers/char/nozomi.c
@@ -853,8 +853,6 @@ static int receive_data(enum port_type index, struct nozomi *dc)
goto put;
}

- tty_buffer_request_room(tty, size);
-
while (size > 0) {
read_mem32((u32 *) buf, addr + offset, RECEIVE_BUF_MAX);

diff --git a/drivers/char/serial167.c b/drivers/char/serial167.c
index 452370a..986aa60 100644
--- a/drivers/char/serial167.c
+++ b/drivers/char/serial167.c
@@ -658,8 +658,7 @@ static irqreturn_t cd2401_rx_interrupt(int irq, void *dev_id)
info->mon.char_max = char_count;
info->mon.char_last = char_count;