Re: [PATCH] gpio: add DT bindings for existing consumer flags

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Thu, Sep 24, 2015 at 11:09 PM, H. Nikolaus Schaller
<hns@xxxxxxxxxxxxx> wrote:
> Am 25.09.2015 um 00:09 schrieb Linus Walleij <linus.walleij@xxxxxxxxxx>:

>> @@ -65,6 +69,13 @@ Example of a node using GPIOs:
>> GPIO_ACTIVE_HIGH is 0, so in this example gpio-specifier is "18 0" and encodes
>> GPIO pin number, and GPIO flags as accepted by the "qe_pio_e" gpio-controller.
>>
>> +Optional standard bitfield specifiers for the last cell:
>> +
>> +- Bit 0: 0 means active high, 1 means active low
>> +- Bit 1: 1 means open drain/open collector, see:
>> +           https://en.wikipedia.org/wiki/Open_collector
>> +- Bit 2: 1 means open source/open emitter
(...)
>> #define GPIO_ACTIVE_HIGH 0
>> #define GPIO_ACTIVE_LOW 1
>> +#define GPIO_OPEN_DRAIN 2
>> +#define GPIO_OPEN_SOURCE 4
>
> this would allow to specify open drain and source
> in parallel (6) - which would mean a completely floating
> output… Is this intended?

OK...

> Some hardware may also have open_collector
> or open_emitter - which is logically the same.
>
> So I have tried to find a common term covering all
> these cases. It appears to be “single-ended”
> https://en.wikipedia.org/wiki/Single-ended_triode
> as opposite to “push-pull" outputs (and “tri-state").

This is good.

> So I would suggest:
>
> #define GPIO_PUSH_PULL 0
> #define GPIO_SINGLE_ENDED 2
>
> and the distinction with pull-down (open drain/collector)
> and pull-up (open source/emitter) to be combined with
> ACTIVE_HIGH/LOW:
>
> #define GPIO_OPEN_DRAIN (GPIO_SINGLE_ENDED  | GPIO_ACTIVE_LOW)
> #define GPIO_OPEN_SOURCE (GPIO_SINGLE_ENDED  | GPIO_ACTIVE_HIGH)

Makes perfect sense. I'll try to fix the patch.

Yours,
Linus Walleij
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