Re: [RFC v2 GPIO lines [was: GPIO User I/O]

[Rodolfo Giometti <giometti@xxxxxxxxxxxx>]

On 19/07/2020 20:35, Andy Shevchenko wrote:
> On Thu, Jul 16, 2020 at 6:17 PM Rodolfo Giometti <giometti@xxxxxxxxxxxx> wrote:
>> On 16/07/2020 15:38, Linus Walleij wrote:
> 
> ...
> 
>> I see but this interface is not designed for such complex usage nor to compete
>> with the current character interface! It is designed to allow boards
>> manufactures to "describe" some I/O lines that are not used by any driver in the
>> device tree,
> 
> Why are they not in firmware tables? Platform is a set of hardware
> that makes it so.
> If something is not in DT, then there is no possible way to know what
> is that line?
> 
> Or in other words how does the OS know that the certain line is
> connected to a relay?

I'm sorry but I'm not sure to understand you.

I think that within the DT the board developer should describe his/her hardware
in the most detailed manner for drivers and, as last step, for the userspace.
The OS should only knows such IO lines whose are driver related while other ones
(such as a relay or a generic digital input such as a lock/unlock signal) should
be described for the userspace.

At the moment the only way to "describe" a digital output/input not related to
any driver is by using the led or uinput interface that are not designed for
such purposes! My suggestion is to give a proper/dedicated description of such
IO lines.

Ciao,

Rodolfo

-- 
GNU/Linux Solutions                  e-mail: giometti@xxxxxxxxxxxx
Linux Device Driver                          giometti@xxxxxxxx
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti