Re: [PATCH v5 01/10] pinctrl: generic: Add bi-directional and output-enable

[Linus Walleij <linus.walleij@linaro.org>]

On Thu, Apr 27, 2017 at 4:56 PM, Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Thu, Apr 27, 2017 at 11:19 AM, Jacopo Mondi
> <jacopo+renesas@jmondi.org> wrote:
>> Add bi-directional and output-enable pin configuration properties.
>>
>> bi-directional allows to specify when a pin shall operate in input and
>> output mode at the same time. This is particularly useful in platforms
>> where input and output buffers have to be manually enabled.
>>
>> output-enable is just syntactic sugar to specify that a pin shall
>> operate in output mode, ignoring the provided argument.
>> This pairs with input-enable pin configuration option.
>
> For me it looks like you are trying to alias open-drain + bias or
> alike. Don't actually see the benefit of it.

Andy is bringing up a valid point. And I remember asking about
this before.

What does "bi-directional" really mean, electrically speaking?

Does is just mean open drain and/or open source actually?
(See Documentation/gpio/driver.txt for an explanation of
how open drain/source works.)

When you set an output without setting a value, what happens
electrically?

Isn't this bias-high-impedance / High-Z?

Hopefully you can find the answer from Renesas hardware dept.

You can certainly call it whatever the datasheet calls it
in your driver #defines but for the DT bindings we would
ideally have the physical world things.

Yours,
Linus Walleij