From: Mike Ditto <mditto@consentry•com>
To: linuxppc-dev@ozlabs•org, linux-i2c@vger•kernel.org,
Timur Tabi <timur@freescale•com>
Subject: Re: Calling wait_event_interruptible_timeout() in I2C wait functions
Date: Wed, 04 Feb 2009 12:00:52 -0800 [thread overview]
Message-ID: <4989F3F4.7070207@consentry.com> (raw)
In-Reply-To: <49889CFA.7070308@freescale.com>
Timur Tabi wrote:
> However, it appears that this is not common behavior for I2C driver. In
> fact, only these six drivers ever call wait_event_interruptible_timeout():
>
> i2c-cpm.c
I don't know about the others, but in i2c-cpm.c the use of interruptible
wait seems incorrect. Maybe it could be made correct, but as is, it
does not correctly clean up the hardware state or return a useful
value when interrupted by a signal. It's not clear what to do, anyway -
it's hard to know which messages of the interrupted transaction have
actually taken effect in the hardware. I think it's better to use
uninterruptible wait here and just live with the delayed signal
handling (one second delay in the unlikely worst case for i2c-cpm).
In general, I think it's best to consider I2C I/O to be uninterruptible,
like disk I/O. The only reason to make it interruptible is to make
sure you don't end up with an unkillable process due to an I/O error,
and that is adequately handled by a timeout (and re-initialization of
the I2C interface in that case).
-=] Mike [=-
next prev parent reply other threads:[~2009-02-04 20:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-03 19:37 Calling wait_event_interruptible_timeout() in I2C wait functions Timur Tabi
2009-02-04 20:00 ` Mike Ditto [this message]
2009-02-05 11:51 ` Mark Brown
2009-02-05 15:18 ` Timur Tabi
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