On 1.6.2021 13.44, Linus Walleij wrote:

On Sun, May 30, 2021 at 6:16 PM Mauri Sandberg [off-list ref] wrote:

quoted

Add documentation for a general GPIO multiplexer.

Signed-off-by: Mauri Sandberg <redacted>
Tested-by: Drew Fustini <redacted>
Reviewed-by: Drew Fustini <redacted>

After some thinking I realized these bindings should not
be restricted to just input. There exist electronic constructions
such as open drain that would make it possible to mux also
outputs.

quoted

  .../bindings/gpio/gpio-mux-input.yaml         | 75 +++++++++++++++++++

Rename it just gpio-mux.yaml

quoted

+$id: http://devicetree.org/schemas/gpio/gpio-mux-input.yaml#

Also here

quoted

+title: Generic GPIO input multiplexer

Generic GPIO multiplexer

quoted

+description: |
+  A generic GPIO based input multiplexer

Not just input

quoted

+  This driver uses a mux-controller to drive the multiplexer and has a single
+  output pin for reading the inputs to the mux.

Make this clearer and do not mention "driver".
Here is a suggestion:

This hardware construction multiplexes (cascades) several GPIO
lines from one-to-many using a software controlled multiplexer.
The most common use case is probably reading several inputs
by switching the multiplexer over several input lines, which in
practice works well since input lines has high impedance.

Constructions with multiplexed outputs are also possible using
open drain electronics.

quoted

+  For GPIO consumer documentation see gpio.txt.

No need to mention this I think, not your problem :D

quoted

+  pin-gpios:

I still want this renamed like in my previous mail.

Hope all is clear!

Yours,
Linus Walleij

Hi and thanks the  comments.

Generally I agree with everything you noted above and elsewhere and will 
make changes
accordingly. But there is a small detail that needs to be sorted out. 
The name 'gpio-mux'
has already been taken by 'mux-gpio' driver [2] [3].

Should we look for another name for this driver and it's bindings or 
refactor the mux-gpio's bindings
first? I would be inclined to do the latter as the config symbol for 
mux-gpio is the same way around,
MUX_GPIO.

The bindings for mux-gpio need to be converted to .yaml anyhow and maybe 
the issues with the schema
that Rob pointed out elsewhere would go away too. Otherwise I cannot 
really say what's wrong as the
errors look unrelated to me.

-- Mauri

[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/mux/gpio-mux.txt
[3] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/mux/gpio.c