linux-kernel - Re: [PATCH] gpiolib: fix oops on reading sysfs exported GPIOs

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Message-ID: <20081016163523.GA27938@oksana.dev.rtsoft.ru>
Date:	Thu, 16 Oct 2008 20:35:23 +0400
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	David Brownell <david-b@...bell.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpiolib: fix oops on reading sysfs exported GPIOs

On Thu, Oct 16, 2008 at 08:43:08AM -0700, David Brownell wrote:
[...]
> > GPIO users should always issue the gpio_direction_input() call and
> > check its return value prior to trying gpio_get_value().
> 
> Not true; the API explicitly allows GPIOs to be treated
> as bidirectional, even when they're configured as outputs.
> That's because most GPIOs *are* bidirectional.

I just recalling somebody was speaking about not wasting cycles with
the checks in the gpio_{set,get}_value(). And the solution was that
before using the gpio_{set,get} one should always try to issue the
"direction" calls to ensure that gpio controller is capable of that
direction... That way gpio_{set,get}_value() don't have to check
anything.

Though I can't find the discussion now, maybe it was a dream... :-)


Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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