linux-kernel - Re: [PATCH] gpiolib: never report open-drain/source lines as 'input' to user-space

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Date:   Tue, 6 Aug 2019 16:23:57 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: never report open-drain/source lines as 'input'
 to user-space

On Tue, Aug 6, 2019 at 1:41 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:

> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>
> If the driver doesn't support open-drain/source config options, we
> emulate this behavior when setting the direction by calling
> gpiod_direction_input() if the default value is 0 (open-source) or
> 1 (open-drain), thus not actively driving the line in those cases.
>
> This however clears the FLAG_IS_OUT bit for the GPIO line descriptor
> and makes the LINEINFO ioctl() incorrectly report this line's mode as
> 'input' to user-space.
>
> This commit modifies the ioctl() to always set the GPIOLINE_FLAG_IS_OUT
> bit in the lineinfo structure's flags field. Since it's impossible to
> use the input mode and open-drain/source options at the same time, we
> can be sure the reported information will be correct.
>
> Fixes: 521a2ad6f862 ("gpio: add userspace ABI for GPIO line information")
> Cc: stable <stable@...r.kernel.org>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>

Patch applied for fixes!
Good catch.

Yours,
Linus Walleij