linux-kernel - Re: [PATCH v5 07/12] leds: leds-gpio: Add support for GPIO descriptors

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Date:	Thu, 30 Oct 2014 16:34:53 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Aaron Lu <aaron.lu@...el.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v5 07/12] leds: leds-gpio: Add support for GPIO descriptors

On Tue, Oct 28, 2014 at 10:56 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Tuesday, October 28, 2014 04:26:25 PM Linus Walleij wrote:
>> On Fri, Oct 17, 2014 at 2:11 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>>
>> > From: Mika Westerberg <mika.westerberg@...ux.intel.com>
>> >
>> > GPIO descriptors are the preferred way over legacy GPIO numbers
>> > nowadays. Convert the driver to use GPIO descriptors internally but
>> > still allow passing legacy GPIO numbers from platform data to support
>> > existing platforms.
>> >
>> > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
>> > Acked-by: Alexandre Courbot <acourbot@...dia.com>
>> > Acked-by: Bryan Wu <cooloney@...il.com>
>> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> (...)
>>
>> >         if (led_dat->blinking) {
>> > -               led_dat->platform_gpio_blink_set(led_dat->gpio,
>> > -                                                led_dat->new_level,
>> > -                                                NULL, NULL);
>> > +               int gpio = desc_to_gpio(led_dat->gpiod);
>> > +               int level = led_dat->new_level;
>>
>> So this desc_to_gpio() is done only to call the legacy callback below?
>>
>> > +               if (gpiod_is_active_low(led_dat->gpiod))
>> > +                       level = !level;
>>
>> And that leads to making it necessary to have this helper variable
>> to invert the level since that callback does not pass a descriptor
>> (which would inherently know if it's active low)....
>>
>> > +
>> > +               led_dat->platform_gpio_blink_set(gpio, level, NULL, NULL);
>>
>> Is it *really* impossible to change all the users of this callback?
>
> You said it could be done in a followup patch.  Here:
> http://marc.info/?l=linux-acpi&m=141154536921643&w=4
>
> And Mika said he would add that to his TODO list:
> http://marc.info/?l=linux-acpi&m=141155173924101&w=4
>
> I suppose that is still valid.

Yes, I *can* be done as follow up, and I still *prefer* that it
be fixed now.

Otherwise I wouldn't keep commenting on it.

>> > +               led_dat->gpiod = gpio_to_desc(template->gpio);
>> > +               if (IS_ERR(led_dat->gpiod))
>> > +                       return PTR_ERR(led_dat->gpiod);
>> >         }
>>
>> OK so this is the legacy codepath: point it out in a big fat
>> comment that this is the legacy codepath.
>
> That looks like it could be done in a followup patch too.

That's not so much work that it can't be done now.

The follow-up patch I mean.

> Since the series is in my linux-next branch at this point, I really wouldn't
> like to reshuffle commits in it if that can be avoided.

That's OK if we just get the follow-up stuff now (the comment patch
immediately!), not in 18 months.

Yours,
Linus Walleij
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