On Tue, Jul 14, 2020 at 03:13:01PM +0800, Chen-Yu Tsai wrote:
> From: Chen-Yu Tsai <wens@csie.org>
> 
> Some LCD panels do not support 24-bit true color, or 8bits per channel
> RGB. Many low end ones only support up to 6 bits per channel natively.
> 
> Add a device tree property to describe the native bit depth of the
> panel. This is separate from the bus width or format of the connection
> to the display output.
> 
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>
> ---
>  .../devicetree/bindings/display/panel/panel-dpi.yaml          | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> index 0cd74c8dab42..8eb013fb1969 100644
> --- a/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> +++ b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> @@ -26,6 +26,9 @@ properties:
>    height-mm: true
>    label: true
>    panel-timing: true
> +  bits-per-color:
> +    description:
> +      Shall contain an integer describing the number of bits per color.

You should specify its type (u32), range (1-8 I guess?) and default
value (which seems to be 8).

Also, it's not unusual to have a different number of bits per color,
like for 16 bits panels where we usually use RGB565. I guess we could
make that an array?

Maxime