* Linus Walleij [off-list ref] [210528 09:08]:

On Thu, May 27, 2021 at 10:33 PM Dario Binacchi [off-list ref] wrote:

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Il 27/05/2021 21:57 Vladimir Zapolskiy [off-list ref] ha scritto:

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Unfortunately you continue to cling to the broken interface, while I see no
comments from you about asked to consider pin groups and pin group functions.

Could you kindly explain to me, with some practical examples, what kind of interface
would you implement ?

I am not fully understanding this discussion.

I get the feeling that this is caused by the early architectural decisions with
pinctrl-single to put all configuration of pin groups and functions per pin into
the device tree.

Tony specifically wanted this because what he gets from TI are some raw
ASIC data dumps from the designers, that he could make a script to process
into device tree rather than into .h files, and get this out of the kernel.
(As I remember it, Tony correct me if I'm wrong.)

Yeah the idea was to avoid stuffing even more SoC specific data into the
kernel and rather use devicetree data only for the booted SoC.
 

This makes it hard to align some concepts of the pin control subsystem such
as functions and groups because pinctrl-single assume a 1-to-1 mapping
between one pin and one group, which in turn has a 1-to-many mapping
to functions.

Is the patch trying to debugfs around this somehow?

If this hack is only needed for pinctrl-single.c then it should be placed in
that driver, so Tony can review it and maintain it as applicable in that
driver's context only, not in the pinctrl core as it appears the general
applicability for other drivers is not there.

Would this really be useful for other drivers than pinctrl-single.c?

I'd rather go with a generic interface. I think it should work if we only
allow enabling and disabling of unclaimed pingroups from sysfs. And then
we can also allow creating new pingroups for unclaimed pins if needed.

Regards,

Tony