linux-kernel - Re: [PATCH 3/5] gpio: make gpiochip_get

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Message-ID: <CAAVeFuJAudOY-s3x38sv13SNo8zfofLWKOKBhKQPYAm1fAj4kw@mail.gmail.com>
Date:	Wed, 23 Jul 2014 12:10:31 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	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>
Subject: Re: [PATCH 3/5] gpio: make gpiochip_get_desc() gpiolib-private

On Wed, Jul 23, 2014 at 5:17 AM, Guenter Roeck <linux@...ck-us.net> wrote:
> On Tue, Jul 22, 2014 at 04:17:41PM +0900, Alexandre Courbot wrote:
>> As GPIO descriptors are not going to remain unique anymore, having this
>> function public is not safe. Restrain its use to gpiolib since we have
>> no user outside of it.
>>
> If I implement a gpio chip driver built as module, and I want to use
> gpiochip_request_own_desc(), how am I supposed to get desc ?
>
> I understand that there is still gpio_to_desc(), but I would have thought
> that
>         desc = gpiochip_get_desc(chip, pin);
> would be better than
>         desc = gpio_to_desc(chip->base + pin);
>
> Not that it makes much of a difference for me, just asking.

Actually I was thinking of changing the prototype of
gpiochip_request_own_desc(), and your comment definitely strenghtens
that idea. gpiochip functions should not work with descriptors,
especially since we are going to switch to a multiple-consumer scheme
where there won't be any canonical descriptor anymore. Thus, how about
turning gpiochip_request_own_desc() into this:

struct gpio_desc *
gpiochip_request_own_desc(struct gpio_chip *chip, u16 hwnum, const char *label);

which would basically do both the gpiochip_get_desc() and former
gpiochip_request_own_desc() in one call. I think it should satisfy
everybody and removes the need to have gpiochip_get_desc() (a not very
useful function by itself) exposed out of gpiolib.

I will send a patch taking care of this if you agree that makes sense.
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