Re: [PATCH v3 3/4] dt-bindings: backlight: Add led-backlight binding

[Jean-Jacques Hiblot]

Pavel,

On 10/07/2019 21:13, Pavel Machek wrote:
> On Wed 2019-07-10 14:39:31, Jean-Jacques Hiblot wrote:
> > Add DT binding for led-backlight.
> >
> > Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxx>
> > ---
> >   .../bindings/leds/backlight/led-backlight.txt | 28 +++++++++++++++++++
> >   1 file changed, 28 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> >
> > diff --git a/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> > new file mode 100644
> > index 000000000000..0444eec8efe1
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> > @@ -0,0 +1,28 @@
> > +led-backlight bindings
> > +
> > +This binding is used to describe a basic backlight device made of
> > LEDs.
> Ok.
>
> > +It can also be used to describe a backlight device controlled by the output of
> > +a LED driver.
> ? The LED driver should better be driving some LEDs...

Well. we are dependent of the board design. If a board designer decided 
to control a backlight with a LED-controller, then we have to deal with it.

In practice there are a lot of LED drivers that actually drive the LEDs 
using PWMs and can be used for this purpose.

JJ

> > +Required properties:
> > +  - compatible: "led-backlight"
> > +  - leds: a list of LEDs
> > +
> > +Optional properties:
> > +  - brightness-levels: Array of distinct brightness levels. The levels must be
> > +                       in the range accepted by the underlying LED devices.
> > +                       This is used to translate a backlight brightness level
> > +                       into a LED brightness level. if not provided, the
> > +                       identity mapping is used.
> "If it is not"
> 									Pavel