Re: Right amount of info in the DT

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Tue, May 9, 2017 at 12:49 PM, Yves Lefloch
<YvesMarie_Lefloch@xxxxxxxxxxxxxxxx> wrote:

> I was wondering what's the recommended approach to
> mutualize code:
> 1. Having a driver under drivers/gpio and another on drivers/pinctrl
>    which depends on the first one.
> 2. Having both drivers in the same file under drivers/pinctrl.
> 3. Having only one pinctrl driver.

All approaches exist. I have no strong opinion, but when possible
try to make separation of concerns.

> For now I've taken approach 3, but isn't it strange to have pins
> dedicated to GPIO like this first group I mentioned controlled
> for a pinctrl driver?
> What is your opinion on this?

Just make sure your driver also provides a gpio_chip and
write good looking code.

>> But I was not meaning you should collect them all under a
>> "pins" node like this, but inside each peripheral.
>
> OK, I will do that. Although not all alternate functions currently
> have a driver, nor a node in the device tree. I guess the best way
> to handle that is to declare the pins as GPIO only and not to worry
> about the alternate function; which brings me back to the question
> above. Do they need a separate GPIO driver?

Implement everything you have a data sheet for even if you
do not use it right now. It is good to have.

Have you read the section "GPIO mode pitfalls" in the documentation?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/pinctrl.txt

It is very important that you know for sure whether it is actual
GPIO or just named that way by some hardware engineer.

Yours,
Linus Walleij
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