linux-kernel - Re: [PATCH] gpio: of_get_named_gpio_flags() return -EPROBE

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Date:	Mon, 18 Jun 2012 17:08:17 +0200
From:	Roland Stigge <stigge@...com.de>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	cjb@...top.org, grant.likely@...retlab.ca, rob.herring@...xeda.com,
	rmk+kernel@....linux.org.uk, ulf.hansson@...ricsson.com,
	linus.walleij@...aro.org, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, aletes.xgr@...il.com,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] gpio: of_get_named_gpio_flags() return -EPROBE_DEFER
 if GPIO not yet available

On 06/18/2012 04:50 PM, Stephen Warren wrote:
>> Can you please tell in which way the patch breaks those drivers?
>> However, I can see that those drivers solved the same problem in a
>> different way (deferring of_get_named_gpio(), via the sound init()). So
>> they could be adjusted to take advantage of new -EPROBE_DEFER.
> 
> The drivers I mentioned test the return code of of_get_named_gpio() to
> see if it's -ENODEV, which means that DT property for that GPIO exists
> but the driver for it isn't available yet, so the property can't be
> parsed. In this case, the sound drivers defer their own probe. If
> of_get_named_gpio() is modified to return -EPROBE_DEFER directly, then
> it won't be returning -ENODEV, and hence the sound drivers' check for
> -ENODEV won't fire, and hence the sound drivers will just continue their
> probe assuming that the particular GPIOs are not present on the board
> (since they are all optional, so anything other than an explicit
> deferral error from of_get_named_gpio() is not treated as an error).
> This will break sound on those platforms.

Thanks for the hint! I previously also suspected sth. like this but
didn't find it in v3.5-rc3. In broonie's sound.git for-next, I now
finally found it.

Should be easy to fix (replacing the if (... == -ENODEV) to -EPROBE_DEFER.

Will you provide patches as signalled, of should I? Which branch would
be the correct one to build on top?

Thanks in advance,

Roland
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