From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
"Claus H . Stovgaard" <cst@phaseone.com>
Subject: Re: [PATCH] gpio: don't WARN() on NULL descs if gpiolib is disabled
Date: Tue, 9 Jul 2019 16:20:24 +0200 [thread overview]
Message-ID: <CAMRc=MfB9R70QDqtjG5a5Roq1roeL78Ss5noytrY-7P=tY1OHA@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdb5xKHZja0mkd-wZJ+YHZpGJaDrkA0dv60MNYKXFcPK4w@mail.gmail.com>
wt., 9 lip 2019 o 15:30 Linus Walleij <linus.walleij@linaro.org> napisał(a):
>
> Hi Bartosz,
>
> On Mon, Jul 8, 2019 at 10:25 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > If gpiolib is disabled, we use the inline stubs from gpio/consumer.h
> > instead of regular definitions of GPIO API. The stubs for 'optional'
> > variants of gpiod_get routines return NULL in this case as if the
> > relevant GPIO wasn't found. This is correct so far.
> >
> > Calling other (non-gpio_get) stubs from this header triggers a warning
> > because the GPIO descriptor couldn't have been requested. The warning
> > however is unconditional (WARN_ON(1)) and is emitted even if the passed
> > descriptor pointer is NULL.
> >
> > We don't want to force the users of 'optional' gpio_get to check the
> > returned pointer before calling e.g. gpiod_set_value() so let's only
> > WARN on non-NULL descriptors.
> >
> > Reported-by: Claus H. Stovgaard <cst@phaseone.com>
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> I remember I had this discussion in the past, and I made a large
> refactoring to make it possible for drivers that need gpiod_*
> calls to simply do:
>
> select GPIOLIB
>
> in Kconfig.
>
> This should solve also this problem I think.
>
> However I do realize that there may be situations where people
> simply want to make GPIO support entirely optional without
> having to e.g. create custom stubs and encapsulate things
> inside if IS_ENABLED(CONFIG_GPIOLIB).
>
In this case the board doesn't provide any GPIO controller at all so
there's simply no need to select GPIOLIB - it would only add bloat.
> I was thinking something like this in the stubs:
>
> gpiod_get[_index]() {
> return POISON;
> }
>
> gpiod_get[_index]_optional() {
> return NULL;
> }
This is already being done.
>
> This way all gpiod_get() and optional calls are properly
> handled and the semantic that only _optional calls
> can return NULL is preserved. (Your patch would
> violate this.)
>
Maybe I'm missing something, but I don't quite see how my patch
violates this behavior. :(
> Then other stubs can do:
>
> gpiod_set_value() {
> WARN_ON(desc);
> }
>
> As in your patch, and all will be smooth provided the
> _optional calls have been used to obtain the desc.
>
> Yours,
> Linus Walleij
Bart
next prev parent reply other threads:[~2019-07-09 14:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 8:23 [PATCH] gpio: don't WARN() on NULL descs if gpiolib is disabled Bartosz Golaszewski
2019-07-08 10:18 ` Claus H. Stovgaard
2019-07-09 13:30 ` Linus Walleij
2019-07-09 14:20 ` Bartosz Golaszewski [this message]
2019-07-16 21:46 ` Linus Walleij
2019-07-20 18:03 ` Bartosz Golaszewski
2019-07-20 19:44 ` Linus Walleij
2019-07-22 6:14 ` Bartosz Golaszewski
2019-07-10 13:09 ` Enrico Weigelt, metux IT consult
2019-07-10 20:02 ` Claus H. Stovgaard
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