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Re: [PATCH][MIPS][3/7] AR7: gpio char device

To: david-b@pacbell.net
Subject: Re: [PATCH][MIPS][3/7] AR7: gpio char device
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Mon, 24 Sep 2007 00:47:01 +0900 (JST)
Cc: technoboy85@gmail.com, nico@openwrt.org, linux-mips@linux-mips.org, akpm@linux-foundation.org
In-reply-to: <20070922185916.BC8122371A7@adsl-69-226-248-13.dsl.pltn13.pacbell.net>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200709201800.53887.technoboy85@gmail.com> <20070923.014201.75184195.anemo@mba.ocn.ne.jp> <20070922185916.BC8122371A7@adsl-69-226-248-13.dsl.pltn13.pacbell.net>
Sender: linux-mips-bounce@linux-mips.org
On Sat, 22 Sep 2007 11:59:16 -0700, David Brownell <david-b@pacbell.net> 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!

---
Atsushi Nemoto

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