Re: [PATCH v2] GPIO: Add gpio_lookup

[Jonathan Corbet <corbet@lwn.net>]

On Mon, 12 Oct 2009 17:11:44 +1100
Ben Nizette <bn@niasdigital.com> wrote:

> Back to this patch though, the gpio names have to come from the platform
> code via some platform_data for the gpio chip [1], the driver then looks
> up that pre-defined name to find the gpio number.  Why not just pass the
> gpio number straight to the end device driver through platform_data and
> bypass the middle-man?

That's true in a situation where you've one One Platform to Bind Them
All, yes.  But if you have (say) GPIOs provided by a PCI-connected
peripheral which are needed in (say) a camera driver, there is no one
platform which can manage all those GPIO numbers.  In particular, I've
done a driver for viafb-based GPIOs; these devices can show up in any
of a number of x86-based systems.  I honestly don't know why it would
make sense to try to hardware numbers to these GPIOs when using names
and dynamic numbering is so much more flexible - and we are already
tracking the names.

Perhaps it would make sense to implement a proper namespace layer for
GPIOs rather than continuing to grow something which evidently sneaked
in through the back door.  Until that's done, though, I think this
patch is useful.  But it it's really unwanted I'll find some other way.

Thanks,

jon