Re: [PATCH] gpio: add gpio_of_helper

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Wed, Oct 22, 2014 at 11:58 AM, Pantelis Antoniou
<panto@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> On Oct 22, 2014, at 12:41 PM, Alexandre Courbot <gnurou@xxxxxxxxx> wrote:

>> Pinmux configuration sounds like a job for pinmux more than GPIO, and
>> exporting potentially many GPIOs to user-space sounds like a work for
>> a proper driver.
>
> I’m afraid that’s not the case. A great many users (...)

How many are many? How long is a piece of string? "Many" may
refer to every system on the market or me and my friends.
That claim has to be more specific.

> do not require anything
> more than setting a pinmux

Which can be done (from device tree if need be) using pin control
hogs.

> and the GPIO configuration (input/output).

And we have GPIO hogs for that in the pipe.

> They can then do low speed I/O using the sysfs interface, without having to
> use any complex APIs (shell works just fine).

So what is added is export capability, which could be done by supplanting
the GPIO hogging mechanism with some linux,export thing.

> Think of stuff like controlling a sprinkler valve, or something like a mechanical
> door detection open state.

OK it's in the department of automatic control, which is arguably the
only technical area where userspace GPIO handling actually makes
sense.

Yours,
Linus Walleij
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