Re: [PATCH 0/6] GPIO character device skeleton

[Markus Pargmann <mpa@pengutronix.de>]

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On Sunday 01 November 2015 11:41:44 Mark Brown wrote:
> On Fri, Oct 30, 2015 at 08:47:14PM +0100, Linus Walleij wrote:
> > On Fri, Oct 30, 2015 at 2:55 AM, Alexandre Courbot <gnurou@gmail.com> wrote:
> 
> > > * For all the justified hate that sysfs got, it had the advantage of
> > > being directly accessible using only the shell. If we replace it with
> > > a character device interface, I think we will need a "libgpio" (that
> > > provides easy access to C programs) and "gpio-tools" (simple
> > > command-line tools that provide functionality similar to the sysfs
> > > interface). Are we ready to start and maintain these? Granted, it
> > > should not be too much work, but it's still an extra.
> 
> > I think the raw ioctl()s will be simple enough and intend to use
> > the tools/gpio/* as proper examples. If we need
> > tools/gpio/swiss-army-knife.c we will add it too.
> 
> > ALSA and fbdev and MESA and libusb spawned huge userspace
> > libs, but I hope this ioctl() ABI will be simple enough that apps
> > can use it directly without a lib. But what do I know.
> 
> That only works for very C like languages, for other languages (things
> like scripting languages in particular) you're going to need a library
> for the language to bind to in order to be usable.

I think we need real gpio userspace tools for such a chardev interface and not
only a library. On the one hand there are all the kernel/userspace developers
that just want to test stuff. On the other hand there are really a lot of
people that are using small embedded devices (e.g. beaglebone, raspberry pi,
...) for really simple applications like using GPIOs to control something. I am
sure many of them are just using some really simple bash code to reach their
goals.

Best Regards,

Markus

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