[PATCH RFC 4/7] [GPIO] Let drivers link if they support GPIO API as an addition

[Anton Vorontsov]

On Fri, Feb 22, 2008 at 03:42:03PM -0800, David Brownell wrote:
> On Monday 10 December 2007, Anton Vorontsov wrote:
> > On Mon, Dec 10, 2007 at 02:55:24PM -0800, David Brownell wrote:
> 
> > > The point of CONFIG_GENERIC_GPIO is to be *the* conditional used to
> > > tell whether that programming interface is available ... starting
> > > from "#include <asm/gpio.h>", and including all gpio_*() calls.
> > > 
> > > So my first reaction is to not like this patch.  It changes semantics
> > > in an incompatible way.  And AFAICT, needlessly so.
> > 
> > Why incompatible? gpio-aware drivers will get -ENOSYS on gpio_request,
> > thus they will not do anything wrong. GPIO-only drivers could still
> > depend on GENERIC_GPIO, and their behaviour will not change.
> 
> If you still want this, I think a better approach would be:
> 
>   http://marc.info/?l=linux-kernel&m=120295461410848&w=2
> 
> That is, #include <linux/gpio.h> and have *that* do the relevant
> switch, based on GENERIC_GPIO.  No semantic changes at all, if
> one discounts the implicit switch to <linux/gpio.h> (important
> for platforms that don't *have* any <asm/gpio.h> header), which
> won't affect any existing code.
> 
> So your NAND code could use that, and work equally well on
> SOC variants that have generic GPIOs and those that don't.
> 
> Comments?

I like it. :-) Thanks.

p.s. would be great to see this in 2.6.25, so we can start use
this include for the new code.

-- 
Anton Vorontsov
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