linux-kernel - Re: [PATCH 2/2] dt-bindings: backlight: document new property default-brightness-level

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Message-ID: <CAH3L5QpPPhCZb5nzfAnunL1qP4Vw_xk_1ovNXaFixa8-aQ3QMw@mail.gmail.com>
Date:   Mon, 29 May 2023 10:03:06 +0300
From:   Alexandru Ardelean <alex@...uggie.ro>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fbdev@...r.kernel.org, lee@...nel.org, jingoohan1@...il.com,
        pavel@....cz, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        deller@....de, Yannick Fertre <yannick.fertre@...s.st.com>,
        Philippe CORNU <philippe.cornu@...s.st.com>
Subject: Re: [PATCH 2/2] dt-bindings: backlight: document new property default-brightness-level

On Fri, May 26, 2023 at 1:20 PM Daniel Thompson
<daniel.thompson@...aro.org> wrote:
>
> On Fri, May 19, 2023 at 11:05:20PM +0300, Alexandru Ardelean wrote:
> > From: Yannick Fertre <yannick.fertre@...s.st.com>
> >
> > Add documentation for new default-brightness-level property.
> >
> > Reviewed-by: Philippe CORNU <philippe.cornu@...s.st.com>
> > Signed-off-by: Yannick Fertre <yannick.fertre@...s.st.com>
> > Signed-off-by: Alexandru Ardelean <alex@...uggie.ro>
> > ---
> >
> > Link to original patch:
> >   https://github.com/STMicroelectronics/linux/commit/c4067d7bd883c6fa14ffd49892c4ce663cdafe98
> >
> >  .../bindings/leds/backlight/gpio-backlight.yaml          | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/leds/backlight/gpio-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/gpio-backlight.yaml
> > index 584030b6b0b9..b96c08cff0f0 100644
> > --- a/Documentation/devicetree/bindings/leds/backlight/gpio-backlight.yaml
> > +++ b/Documentation/devicetree/bindings/leds/backlight/gpio-backlight.yaml
> > @@ -23,6 +23,15 @@ properties:
> >      description: enable the backlight at boot.
> >      type: boolean
> >
> > +  default-brightness-level:
> > +    description:
> > +      The default brightness level (index into the array defined by the
> > +      "brightness-levels" property).
>
> gpio-backlight does not have a brightness-levels array property!
>
> I think it is also necessary to improve the docs of both properties to
> distinguish between the meaning of default-on and
> default-brightness-level. The result of setting default-on and
> default-brightness level to zero is that the GPIO will be off (this is
> correct behaviour but hard to figure out from the current text).
>
> default-on is a control that can "enable" the backlight at boot when it
> is not linked to a display in the DT (e.g. it is mostly for legacy
> cases). When the backlight is linked to a display then the backlight
> enable state will be automatically linked to the display enable state
> instead.
>
> default-brightness-level is useful for handling displays that
> are still readable with the backlight off (e-ink, reflective/
> transflexive LCD, etc), otherwise is should be absent or set to 1.

ack
will do in V2

thanks

>
>
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +dependencies:
> > +  default-brightness-level: [ "brightness-levels" ]
>
> As above, depending on brightness-levels doesn't make any sense here.
>
>
> Daniel.