Re: [PATCH] Documentation: gpio: guidelines for bindings

From: Alexandre Courbot
Date: Tue Oct 28 2014 - 05:19:00 EST


On Tue, Oct 28, 2014 at 6:08 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Tuesday 28 October 2014 13:20:34 Alexandre Courbot wrote:
>> +GPIO properties should be named "[<name>-]gpios", with <name> being the con_id
>> +argument that is passed to gpiod_get(). While a NULL con_id is accepted by the
>> +GPIO API for compatibility reasons (resolving to the "gpios" property), it is
>> +not allowed for new bindings.
>> +
>> +GPIO properties can contain one or more GPIO phandles, but only in exceptional
>> +cases should they contain more than one. If your device uses several GPIOs with
>> +distinct functions, reference each of them under its own property, giving it a
>> +meaningful name. The only case where an array of GPIOs is accepted is when
>> +several GPIOs serve the same function (e.g. a parallel data line). In that case
>> +individual GPIOs can be retrieved using gpiod_get_index().
>> +
>> +The exact meaning of each gpios property must be documented in the device tree
>> binding for each device.
>
> The binding should be written in an OS neutral way, so it would be better to avoid
> direct references to Linux APIs in the part that specifies the allowed properties.
>
> Could you reword this so the Linux interfaces are described in an "implementation
> notes" section that is separate from the main part?

You're right - will fix this and resubmit. Thanks!
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