On Mi, 2016-07-06 at 14:34 +0200, Linus Walleij wrote:

On Wed, Jul 6, 2016 at 12:27 PM, Johan Hovold [off-list ref] wrote:

quoted

What's wrong with naming the pins in DT and use that for lookups?

That works. It relies on the developers using sane naming conventions
though. (This problem is prevalent everywhere I guess, a human problem,
not a technical one.) I made this patch:
http://marc.info/?l=linux-arm-kernel&m=146672328215354&w=2

There is a standard document for these boards (96board) specifying
the names of the GPIO lines to be "GPIO-A" thru "GPIO-L".

So a user can iterate across the gpiochips (as is done in lsgpio)
and pick the lines with the right names.

This discussion caused me remember a concern regarding the chardev
interface: Is it still be possible to give specific users/groups access
to individual GPIOs? This is currently possible in the sysfs interface
with chown/chmod. I don't see how per-GPIO permissions would translate
to a per-gpiochip device.

Am I overlooking some better way to give non-root users granular access
to GPIOs? Or is that intentionally out of scope for the chardev
interface?

Yours,
Jan
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