From: Mike Frysinger <email@example.com>
To: Li Yi <firstname.lastname@example.org>
Cc: Andrew Morton <email@example.com>,
Subject: Re: [PATCH 1/2] spi: new SPI bus lock/unlock functions
Date: Mon, 21 Sep 2009 09:36:25 -0400 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On Mon, Sep 21, 2009 at 02:33, Li Yi wrote:
> On Fri, 2009-09-18 at 14:29 -0700, Andrew Morton wrote:
>> On Thu, 17 Sep 2009 18:03:16 -0400
>> Mike Frysinger <email@example.com> wrote:
>> > From: Yi Li <firstname.lastname@example.org>
>> > For some MMC cards over SPI bus, it needs to lock the SPI bus for its own
>> > use. The SPI transfer must not be interrupted by other SPI devices that
>> > share the SPI bus with SPI MMC card.
>> > This patch introduces 2 APIs for SPI bus locking operation.
>> > Signed-off-by: Yi Li <email@example.com>
>> > Signed-off-by: Bryan Wu <firstname.lastname@example.org>
>> > Signed-off-by: Mike Frysinger <email@example.com>
>> > ---
>> > Andrew: we've posted these in the past with no response. could you pick
>> > them up please ?
>> > drivers/spi/spi.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++
>> > include/linux/spi/spi.h | 7 ++++++
>> > 2 files changed, 55 insertions(+), 0 deletions(-)
>> > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
>> > index 70845cc..b82b8ad 100644
>> > --- a/drivers/spi/spi.c
>> > +++ b/drivers/spi/spi.c
>> > @@ -653,6 +653,54 @@ static void spi_complete(void *arg)
>> > }
>> > /**
>> > + * spi_lock_bus - lock SPI bus for exclusive access
>> > + * @spi: device which want to lock the bus
>> > + * Context: any
>> > + *
>> > + * Once the caller owns exclusive access to the SPI bus,
>> > + * only messages for this device will be transferred.
>> > + * Messages for other devices are queued but not transferred until
>> > + * the bus owner unlock the bus.
>> > + *
>> > + * The caller may call spi_lock_bus() before spi_sync() or spi_async().
>> > + * So this call may be used in irq and other contexts which can't sleep,
>> > + * as well as from task contexts which can sleep.
>> Hence spi_lock_bus() basically has to use a spinning lock?
>> So code which has called spi_lock_bus() cannot sleep until it calls
>> That's worth mentioning in the description.
> Code called spi_lock_bus() _can_ sleep. This is mentioned in the
should add might_sleep() to the common spi_lock_bus() function then.
next prev parent reply other threads:[~2009-09-21 13:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-17 22:03 [PATCH 1/2] spi: new SPI bus lock/unlock functions Mike Frysinger
2009-09-17 22:03 ` [PATCH 2/2] mmc_spi: lock the SPI bus when accessing the card Mike Frysinger
2009-09-18 0:29 ` [spi-devel-general] [PATCH 2/2] mmc_spi: lock the SPI bus whenaccessing " H Hartley Sweeten
2009-09-18 0:52 ` [PATCH 2/2 v2] mmc_spi: lock the SPI bus when accessing " Mike Frysinger
2009-09-18 21:30 ` Andrew Morton
2009-09-17 22:45 ` [spi-devel-general] [PATCH 1/2] spi: new SPI bus lock/unlockfunctions H Hartley Sweeten
2009-09-17 22:53 ` Mike Frysinger
2009-09-18 23:00 ` H Hartley Sweeten
2009-09-19 19:11 ` Mike Frysinger
2009-09-21 8:08 ` Li Yi
2009-09-18 21:29 ` [PATCH 1/2] spi: new SPI bus lock/unlock functions Andrew Morton
2009-09-21 6:33 ` Li Yi
2009-09-21 13:36 ` Mike Frysinger [this message]
2009-09-22 14:15 ` Mike Frysinger
2009-12-16 22:49 ` [spi-devel-general] [PATCH 1/2] spi: new SPI bus lock/unlockfunctions H Hartley Sweeten
2009-12-16 23:00 ` Mike Frysinger
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).