Re: [PATCH] gpio: add gpio_of_helper

["Jiří Prchal" <jiri.prchal@aksignal.cz>]

Hi all,

Dne 28.10.2014 v 18:28 Pantelis Antoniou napsal(a):
> Hi Linus,
>
>> On Oct 28, 2014, at 19:09 , Linus Walleij <linus.walleij@linaro.org> wrote:
>>
>> On Wed, Oct 22, 2014 at 11:58 AM, Pantelis Antoniou
>> <panto@antoniou-consulting.com> wrote:
>>>> On Oct 22, 2014, at 12:41 PM, Alexandre Courbot <gnurou@gmail.com> 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.
>>
>
> On every embedded product board that I have worked on for a customer,
> invariably user-space GPIO was required for some odd pieces of hardware.
>
> I guess that’s in the dozen range for me, and Jiri that originally posted
> seems to be doing something similar too.
Yes.
>
>>> 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.
>>
>
> The original proposal was on January, and there’s a RFC posted just a few days back.
> I will take a look.
>
>>> 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.
>>
>
> Yes, that would be nice.
That would be nice for me too, I'll try it later, now I have more urgent work.
>
>>> 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.
>>
>
> Err, let’s just say that I completely disagree, but whatever.
>
> If the new GPIO hogging methods make it in mainline along with the export
> mechanism it’d be fine by me.
>
>> Yours,
>> Linus Walleij
>
> Regards
>
> — Pantelis

Yours
Jiri
>
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