On Mon, Dec 15, 2014 at 10:57 PM, Arnd Bergmann [off-list ref] wrote:

On Monday 15 December 2014 13:35:47 Ray Jui wrote:

quoted

Like I said previously, dynamic GPIO allocation works fine in the
kernel, as long as all of our GPIO clients in the kernel use gpiod based
API, which is what we will enforce going forward. The only problem is
with some of our customers who use GPIO through sysfs and expect fixed
global GPIO numbers. Thinking about this more, it's probably not that
difficult to add a script for those customers to convert/map the GPIO
numbers based on readings parsed from sysfs, so I guess that's fine.

I think we discussed the user space interface a number of times
in the past, but I forgot the outcome. Either there is already
a way to name gpio lines uniquely in sysfs, or there should be
one.

There is one. The struct gpio_chip contains a .names field with
strings giving names to the GPIOs on the chip.

This field does not have standardized DT bindings or anything
but should be used.

Overall the sysfs interface is an abomination for relying on
the notoriously unstable GPIO numberspace and other things.
It was merged when the subsystem lacked a maintainer.

Yours,
Linus Walleij