linux-kernel - Re: [PATCH 08/23] gpio: remove gpiod_sysfs_set_active

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Date:	Mon, 27 Apr 2015 17:34:38 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Johan Hovold <johan@...nel.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jonathan Corbet <corbet@....net>,
	Harry Wei <harryxiyou@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	linux-kernel@...kernel.org, linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 08/23] gpio: remove gpiod_sysfs_set_active_low

On Mon, Apr 27, 2015 at 5:16 PM, Johan Hovold <johan@...nel.org> wrote:
> On Mon, Apr 27, 2015 at 12:54:15PM +0900, Alexandre Courbot wrote:
>> On Wed, Apr 22, 2015 at 12:42 AM, Johan Hovold <johan@...nel.org> wrote:
>> > Remove gpiod_sysfs_set_active_low (and gpio_sysfs_set_active_low) which
>> > allowed code to change the polarity of a gpio line even after it had
>> > been exported through sysfs.
>> >
>> > Drivers should not care, and generally does not know, about gpio-line
>> > polarity which is a hardware feature that needs to be described by
>> > firmware.
>> >
>> > It is currently possible to define gpio-line polarity in device-tree and
>> > acpi firmware or using platform data. Userspace can also change the
>> > polarity through sysfs.
>> >
>> > Note that drivers using the legacy gpio interface could still use
>> > GPIOF_ACTIVE_LOW to change the polarity before exporting the gpio.
>> >
>> > There are no in-kernel users of this interface.
>> >
>> > Cc: Jonathan Corbet <corbet@....net>
>> > Cc: Harry Wei <harryxiyou@...il.com>
>> > Cc: Arnd Bergmann <arnd@...db.de>
>> > Cc: linux-doc@...r.kernel.org
>> > Cc: linux-kernel@...kernel.org
>> > Cc: linux-arch@...r.kernel.org
>> > Signed-off-by: Johan Hovold <johan@...nel.org>
>> > ---
>
>> > diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
>> > index 31434c5a90ef..8a95a954f514 100644
>> > --- a/drivers/gpio/gpiolib-sysfs.c
>> > +++ b/drivers/gpio/gpiolib-sysfs.c
>> > @@ -293,8 +293,8 @@ static int sysfs_set_active_low(struct gpio_desc *desc, struct device *dev,
>> >                 clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
>> >
>> >         /* reconfigure poll(2) support if enabled on one edge only */
>> > -       if (dev != NULL && (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
>> > -                               !!test_bit(FLAG_TRIG_FALL, &desc->flags))) {
>> > +       if (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
>> > +                               !!test_bit(FLAG_TRIG_FALL, &desc->flags)) {
>>
>> This change seems to be unrelated to this patch...
>
> This helper is now only called from the attribute operation and dev
> will never be NULL.
>
> On the other hand, it was never called with a NULL argument before this
> patch either (the test has always been bogus). Let me know if you prefer
> this bit to be a separate patch.

Nope, after reading your explanation I understand why you want to have
this here. Thanks for clarifying!
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