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

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Date:	Mon, 27 Apr 2015 10:16:29 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Alexandre Courbot <gnurou@...il.com>
Cc:	Johan Hovold <johan@...nel.org>,
	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 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.

> Otherwise, I agree and good riddance!

Thanks,
Johan
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