lkml.org 
[lkml]   [2011]   [Aug]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRE: [PATCH 1/3] irq: If an IRQ is a GPIO, request and configure it
Mark Brown wrote at Thursday, August 04, 2011 11:35 PM:
> On Thu, Aug 04, 2011 at 08:53:34PM -0700, Stephen Warren wrote:
>
> > Well, things break. This is essentially the problem I was describing in
> > the PATCH 0 email, just with a slightly different motivation.
>
> There's a bunch of existing code using that idiom.

Certainly.

> > I suppose that an alternative here would be to simply ignore any errors
> > from gpio_request. This might have the benefit of removing the need for
> > the other two patches I posted in the series. However, it seems a little
> > dirty; one benefit of the IRQ code calling gpio_request and honoring
> > errors would be to detect when some completely unrelated code had a bug
> > and had called gpio_request on the GPIO before. Such detection would be
> > non-existent if we don't error out on gpio_request. Perhaps some mechanism
> > is needed to indicate that the driver has explicitly already called
> > gpio_request for a legitimate shared purpose, and only then ignore
> > errors?
>
> But it's not a bug to use a GPIO as an IRQ source, otherwise we wouldn't
> have gpio_to_irq() in the first place.

True, but I think there are two cases:

1) Some code legitimately uses a pin as both a GPIO and IRQ, and is fully
cognizant of the fact, just like in your example -> no bug.

2) Two pieces of unrelated code somehow accidentally get a GPIO and IRQ
number that map to the same resource, e.g. due to incorrect board files or
Device Tree content. This is probably a bug, but ends up looking exactly
the same as far as the IRQ code's gpio_request call failing in the patch I
posted.

> Feels like we need a backchannel
> between gpiolib and the IRQ code to do this. Or perhaps the drivers
> that implement this should be taking care of setting up the GPIO mode?

--
nvpublic



\
 
 \ /
  Last update: 2011-08-05 17:33    [W:0.052 / U:0.080 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site