linux-kernel - Re: [PATCH] gpiolib: return -ENOENT when no GPIO mapping exists

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Date:	Mon, 9 Dec 2013 14:40:18 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpiolib: return -ENOENT when no GPIO mapping exists

On Fri, Dec 06, 2013 at 11:06:56AM +0900, Alexandre Courbot wrote:
> Some devices drivers make use of optional GPIO parameters. For such
> drivers, it is important to discriminate between the case where no
> GPIO mapping has been defined for the function they are requesting, and
> the case where a mapping exists but an error occured while resolving it
> or when acquiring the GPIO.
> 
> This patch changes the family of gpiod_get() functions such that they
> will return -ENOENT if and only if no GPIO mapping is defined for the
> requested function. Other error codes are used when an actual error
> occured during the GPIO resolution.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
> I think this change should be merged early as not having it may prevent
> some users to switch to gpiod. I stumbled upon this issue while
> considering porting a simple driver (pwm_bl) that has an optional GPIO
> parameter.
> 
> Mika, Andy: if Linus agrees with this change, could you take care of
> having -ENOENT returned as well for the ACPI and SFI GPIOs lookup?

Sure. I have a patch for this already so once this gets merged, I'll send
out the ACPI version.
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