Re: gpio_is_valid()

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Mon, Mar 29, 2021 at 4:31 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>
> On Mon, Mar 29, 2021 at 12:50 PM Andy Shevchenko
> <andy.shevchenko@xxxxxxxxx> wrote:
>
> > Anybody to shed a light why we have two stubs of gpio_is_valid() and
> > one actual declaration?
> > % git grep -n -w gpio_is_valid -- include/
> > include/asm-generic/gpio.h:44:static inline bool gpio_is_valid(int number)
> > include/asm-generic/gpio.h:143:static inline bool gpio_is_valid(int number)
> > include/linux/gpio.h:109:static inline bool gpio_is_valid(int number)
>
> Remnants from "generic GPIO" where some custom platform would have
> a custom implementation (and semantic!) while using the same
> API.
>
> include/linux/gpio.h:109 - this is just a stub !CONFIG_GPIOLIB
>
> include/asm-generic/gpio.h:44 - this one is used if CONFIG_GPIOLIB
>
> This is for all "normal" GPIO providers and consumers, end of
> story.
>
> include/asm-generic/gpio.h:143 - this one is used of !CONFIG_GPIOLIB
> but only <asm/gpio.h> is included, meaning the system has a
> private implementation of the symbols, not those from GPIOLIB.

Aha, thanks for elaboration!

> It makes sense if you realize there are GPIO drivers that only include
> <asm/gpio.h> and does not include <linux/gpio.h>. But I wonder if
> there still are? (Unfortunately I think so, used to be some weird archs
> and some minor ARM systems.)

The files so far that include asm/gpio.h

Documentation/translations/zh_CN/gpio.txt
drivers/gpio/Kconfig
include/asm-generic/gpio.h
include/linux/gpio.h

> Generic GPIO was probably not a very good idea, I think at the time
> it was a compromise for making custom implementations migrate
> to the generic implementation over time.
>
> I think it is actually gone now! We can probably delete:
> arch/arm/include/asm/gpio.h
> include/asm-generic/gpio.h
>
> And just move the remaining stubs into <linux/gpio.h>.
>
> Interested in the job or should I take a stab at it? :D

I think it's you who understands the area better.
I missed (I hope *fortunately*) the legacy GPIO APIs.

-- 
With Best Regards,
Andy Shevchenko