Hi Conor,

...

On Fri, Oct 20, 2023 at 03:54:33PM +0200, Flavio Suligoi wrote:

quoted

The two properties:

- max-brightness
- default brightness

are not really required, so they can be removed from the "required"
section.

Why are they not required? You need to provide an explanation.

The "max-brightness" is not more used now in the driver (I used it in the first version
of the driver).
The "default-brightness", if omitted in the DT, is managed by the device driver,
using a default value. This depends on the dimming mode used:

- for the "analog mode", via I2C commands, this value is fixed by hardware (=31)
- while in case of pwm mode the default used is the last value of the 
  brightness-levels array.

Also the brightness-levels array is not required; if it is omitted, the driver uses 
a default array of 0..255 and the "default-brightness" is the last one, which is "255".

quoted

Other changes:

- improve the backlight working mode description, in the "description"
  section

quoted

- update the example, removing the "max-brightness" and introducing the
  "brightess-levels" property

Why is this more useful?

I introduced the "brightness-levels" instead of "max-brightness" for homogeneity,
since the "analog mode" dimming has a brightness-levels array fixed by hardware (0..31).
In this way also the "pwm" mode can use the same concepts of array of levels.

Cheers,
Conor.

Thanks for your help.
Flavio.

quoted

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
---
 .../bindings/leds/backlight/mps,mp3309c.yaml           | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git

a/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml
b/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml

quoted

index 4191e33626f5..527a37368ed7 100644
---

a/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml

quoted

+++

b/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml

quoted

@@ -14,8 +14,8 @@ description: |
   programmable switching frequency to optimize efficiency.
   It supports two different dimming modes:

-  - analog mode, via I2C commands (default)
-  - PWM controlled mode.
+  - analog mode, via I2C commands, as default mode (32 dimming levels)
+  - PWM controlled mode (optional)

   The datasheet is available at:
   https://www.monolithicpower.com/en/mp3309c.html

@@ -50,8 +50,6 @@ properties:
 required:
   - compatible
   - reg
-  - max-brightness
-  - default-brightness

 unevaluatedProperties: false

@@ -66,8 +64,8 @@ examples:
             compatible = "mps,mp3309c";
             reg = <0x17>;
             pwms = <&pwm1 0 3333333 0>; /* 300 Hz --> (1/f) * 1*10^9 */
-            max-brightness = <100>;
-            default-brightness = <80>;
+            brightness-levels = <0 4 8 16 32 64 128 255>;
+            default-brightness = <6>;
             mps,overvoltage-protection-microvolt = <24000000>;
         };
     };
--

2.34.1