[PATCH] drivers: create a pin control subsystem v8

[Mike Frysinger]

On Tue, Oct 4, 2011 at 16:35, Grant Likely wrote:
> On Sat, Oct 01, 2011 at 12:39:21PM +0200, Linus Walleij wrote:
>> 2011/9/30 Grant Likely:
>> > I'm not convinced that the sysfs approach is
>> > actually the right interface here (I'm certainly not a fan of the gpio
>> > sysfs i/f), and I'd rather not be putting in unneeded stuff until the
>> > userspace i/f is hammered out.
>>
>> Actually, thinking about it I cannot see what would be wrong
>> with /dev/gpio0 & friends in the first place.
>>
>> Using sysfs as swiss army knife for custom I/O does not
>> seem like it would be long-term viable so thanks for this
>> observation, and I think we need /dev/gpio* put on some
>> mental roadmap somewhere.
>
> Agreed.  I don't want to be in the situation we are now with GPIO,
> where every time I look at the sysfs interface I shudder.

the problem with that is it doesn't scale.  if i have a device with
over 150 GPIOs on the SoC itself (obviously GPIO expanders can make
that much bigger), i don't want to see 150+ device nodes in /dev/.
that's a pretty big waste.  sysfs only allocates/frees resources when
userspace actually wants to utilize a GPIO.
-mike