Re: [PATCH 0/2] gpio: Allow userspace export from DT

[Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>]

On Mon, May 04, 2015 at 10:49:25AM +0200, Johan Hovold wrote:
> Firmware should describe pin directionality and function, and undefined
> pins should never be allowed to be accessed from userspace.

No, that's totally wrong if you consider one of the most common use
cases out there...

Think about something like a Raspberry Pi, where you have a header with
GPIOs on it, which can be used for multiple different purposes (and are
even multiplexed with some on-SoC functions.)

"Firmware" can't know about all possible configurations of those IO pins.

That's why Raspberry Pi uses a userspace helper and programs stuff up
appropriately for the users application.

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