On Sat, 22 Sep 2007 11:59:16 -0700, David Brownell <firstname.lastname@example.org> wrote:
> > I think there were some discussions about userspace API for GPIO on
> > LKML, but cannot remember the detail.
> > David, give us a comment please?
> It's not yet platform-neutral even given those issues; see below.
> And it's insufficient by itself, which is the main technical point
> I'd raise: without even udev/mdev hooks, it needs manual setup.
> I don't think anyone has yet *proposed* a platform-neutral userspace
> interface to GPIOs yet. They all seem to include at least platform
> specific pinmux setup ... which is probably inevitable, but that
> would seem to need abstracting into platform-specific hooks.
> There have been a few folk expressing interest in a userspace GPIO
> interface, and a few system-specific examples. The most flexible ones
> that come to mind are on Gumstix PXA2xx boards. One enables GPIO
> IRQs through a gpio-events module; and a /proc/gpio/GPIOnn interface
> monitors all the pins and their configurations (which may mean they
> aren't used for GPIOs at all). On some AVR32 boards, Atmel had a
> (less capable) configfs interface, mostly used for LED access.
Thank you pointing out those issues. It seems things are much
complicated than I was thinking of...
> More detailed comments are embedded below.
And these comments help us understanding how to use and implement the
GPIO API. Thanks!