linux-kernel - Re: [PATCH] gpio: add flags argument to gpiod

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Message-ID: <CAAVeFuJm6EOseDow9Mr27FaqucdARaQvXTb3FxA13kqnRw3a3w@mail.gmail.com>
Date:	Mon, 4 Aug 2014 14:04:12 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	Mark Brown <broonie@...nel.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: add flags argument to gpiod_get*() functions

On Thu, Jul 31, 2014 at 12:43 PM, Alexandre Courbot <gnurou@...il.com> wrote:
> On Mon, Jul 28, 2014 at 7:30 PM, Linus Walleij <linus.walleij@...aro.org> wrote:
>> On Fri, Jul 25, 2014 at 4:38 PM, Alexandre Courbot <acourbot@...dia.com> wrote:
>>
>>> The huge majority of GPIOs have their direction and initial value set
>>> right after being obtained by one of the gpiod_get() functions. The
>>> integer GPIO API had gpio_request_one() that took a convenience flags
>>> parameter allowing to specify an direction and value applied to the
>>> returned GPIO. This feature greatly simplifies client code and ensures
>>> errors are always handled properly.
>>>
>>> A similar feature has been requested for the gpiod API. Since setting
>>> the direction of a GPIO is so often the very next action done after
>>> obtaining its descriptor, we prefer to extend the existing functions
>>> instead of introducing new functions that would raise the
>>> number of gpiod getters to 16 (!).
>>>
>>> The drawback of this approach is that all gpiod clients need to be
>>> updated. To limit the pain, temporary macros are introduced that allow
>>> gpiod_get*() to be called with or without the extra flags argument. They
>>> will be removed once all consumer code has been updated.
>>>
>>> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
>>> ---
>>> This dude can be applied harmlessly to the GPIO tree - then I will go
>>> after every gpiod user to update the calls to gpiod_get*() before
>>> removing the macros in consumer.h.
>>
>> OK I trust you. Patch applied with Broonie's review tag.
>
> Thanks! Unfortunately it is still not in -next due to a build error...
>
>> Just so we don't forget how we should move forward: Alex what do
>> you think about adding a drivers/gpio/TODO.TXT file outlining the
>> overall plan of the gpiod refactoring and clean-up work?
>
> I have such a file locally - I'm not sure if checking it into the
> kernel tree is relevant though. Sounds more like the task of a wiki
> page.

FWIW I have posted a small list of stuff I intent to do shortly:
https://gist.github.com/Gnurou/a62915acbfe0d0d4a671
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