linux-kernel - Re: [PATCH RESEND] gpio: Add support for GPIOF_ACTIVE_LOW to gpio_request

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Message-ID: <CACRpkdbn+nNJ4L71ZkLzNWWvmAq=bTYTBg1AJWe7TAtGq+3pKw@mail.gmail.com>
Date:	Wed, 23 Jul 2014 17:32:42 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH RESEND] gpio: Add support for GPIOF_ACTIVE_LOW to
 gpio_request_one functions

On Mon, Jul 21, 2014 at 8:12 PM, Guenter Roeck <linux@...ck-us.net> wrote:

> The gpio include file and the gpio documentation declare and document
> GPIOF_ACTIVE_LOW as one of the flags to be passed to gpio_request_one
> and related functions. However, the flag is not evaluated or used.
>
> This can cause problems in at least two areas: First, the same API can
> be used to auto-export pins to user space. The missing support for
> GPIOF_ACTIVE_LOW results in unexpected behavior for such auto-exported
> pins. Second, the requested gpio pin can be convered for use by
> gpiod functions with gpio_to_desc(). While gpio API functions do not
> support GPIOF_ACTIVE_LOW, gpiod functions do, which again results in
> unexpected behavior.
>
> Check the flag in gpio_request_one and set the gpio internal flag
> FLAG_ACTIVE_LOW if it is set to address those problems.
>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> Reviewed-by: Alexandre Courbot <acourbot@...dia.com>

Patch applied after manually rebasing so it hits gpiolib-legacy.c.

Yours,
Linus Walleij
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