Hi Alexander,
On Wed, May 31, 2023 at 8:19 AM Alexander Stein
<alexander.stein@xxxxxxxxxxxxxxx> wrote:
> Am Dienstag, 30. Mai 2023, 17:19:45 CEST schrieb Uwe Kleine-König:
> > For active low lines the semantic of output-low and output-high is hard
> > to grasp because there is a double negation involved and so output-low
> > is actually a request to drive the line high (aka inactive).
> >
> > So introduce output-inactive and output-active with the same semantic as
> > output-low and output-high respectively have today, but with a more
> > sensible name.
> >
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> > ---
> > Documentation/devicetree/bindings/gpio/gpio.txt | 16 +++++++++++-----
> > 1 file changed, 11 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt
> > b/Documentation/devicetree/bindings/gpio/gpio.txt index
> > d82c32217fff..2f037bbd3ffa 100644
> > --- a/Documentation/devicetree/bindings/gpio/gpio.txt
> > +++ b/Documentation/devicetree/bindings/gpio/gpio.txt
> > @@ -209,15 +209,21 @@ Required properties:
> > - gpios: Store the GPIO information (id, flags, ...) for each GPIO to
> > affect. Shall contain an integer multiple of the number of
> cells
> > specified in its parent node (GPIO controller node).
> > +
> > Only one of the following properties scanned in the order shown below.
> > This means that when multiple properties are present they will be searched
> > in the order presented below and the first match is taken as the intended
> > configuration.
> > -- input: A property specifying to set the GPIO direction as input.
> > -- output-low A property specifying to set the GPIO direction as output
> > with - the value low.
> > -- output-high A property specifying to set the GPIO direction as output
> > with - the value high.
> > +- input: A property specifying to set the GPIO direction as
> > input. +- output-inactive: A property specifying to set the GPIO
> > direction as output + with the inactive value
> (depending on the
> > line's polarity, + which is active-high by default)
> > +- output-active: A property specifying to set the GPIO direction as
> > output + with the active value.
>
> I know this is essentially just renaming currently existing properties.
> But these mutual exclusive (boolean) properties make it impossible to change
> them in DT overlay. Any ideas how to support changing the output level onGPIO
> hogs in DT overlay?
That's a good point. And despite it not working, people do try to
stick e.g. /delete-node/ in .dtso files...
I assume you can sort of remove the existing hog subnode by adding
status = "disabled" in the DT overlay, and adding a new subnode to
configure the new output level?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
