Re: Userspace and Device-Tree

[Alexandre Courbot <gnurou-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

>> Similarly, I'd like to be able to signal the export of a GPIO to userspace
>> (/sys/class/gpio/gpioWXY) without a customized board file.  Since we're
>> using DT to specify the hardware in a system, it would be a convenient place
>> to specify exporting GPIOs to userspace.
>
> I believe that the GPIO subsystem maintainers (Linus Walleij and
> Alexandre Courbot) were trying to make GPIO control from userspace more
> consistent (independent of DT) for a while. However I am not all that
> familiar with the GPIO subsystem and may have misunderstood some of the
> work that's going on there.

If I properly understood what Chris wants, he may want to have a look
at the following works:

- GPIO hogging mechanism to configure a GPIO using the device tree -
not sure if you can also export at that time?
- Markus' ongoing work on GPIO naming:
http://www.spinics.net/lists/linux-gpio/msg07844.html
- Device tree overlays, to separate the configuration of GPIOs for
user-space use (which is arguably specific to one's use case) from the
rest of the board's definition

With these 3 works I think Chris' needs would be fulfilled, at least
as far as GPIOs are concerned.
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