Re: [PATCH 2/2] dt-bindings: display: simple-framebuffer: Document mono format

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 04.11.26 um 03:34 schrieb Sebastian Raase:
> This is a 1 bit-per-pixel monochrome format, with 8 pixels/byte.
>
> Signed-off-by: Sebastian Raase <linux@sraa.de>
> ---
>   .../devicetree/bindings/display/simple-framebuffer.yaml         | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/simple-framebuffer.yaml b/Documentation/devicetree/bindings/display/simple-framebuffer.yaml
> index 45ffdebc9d86..c627ec088434 100644
> --- a/Documentation/devicetree/bindings/display/simple-framebuffer.yaml
> +++ b/Documentation/devicetree/bindings/display/simple-framebuffer.yaml
> @@ -94,6 +94,7 @@ properties:
>     format:
>       description: >
>         Format of the framebuffer:
> +        * `mono` - 1-bit packed pixels, 8 pixels/byte

I don't object the change, but I really object the naming.

Mono is not a good name because it doesn't describe the format's pixel 
layout. For example, RGB with only 2 colors is also mono in some sense.

The common names used in the Linux kernel for this type of color format 
are C1 and R1. More generally speaking,

  - Cn describes an n-bit format with a palette. The pixel bits index 
into the palette.  Pixels are packed.
  - Rn describes an n-bit format with a single color channel. The 
channel has linear color gradient. Pixels are packed.

In your case, you'd define 'r1'. While at it, we can also define r2, r4, 
and r8.  The terminal supports up to 16 colors, so implementing r4 might 
be of interest to some simple hardware.

Best regards
Thomas


>           * `a1r5g5b5` - 16-bit pixels, d[15]=a, d[14:10]=r, d[9:5]=g, d[4:0]=b
>           * `a2r10g10b10` - 32-bit pixels, d[31:30]=a, d[29:20]=r, d[19:10]=g, d[9:0]=b
>           * `a8b8g8r8` - 32-bit pixels, d[31:24]=a, d[23:16]=b, d[15:8]=g, d[7:0]=r
> @@ -106,6 +107,7 @@ properties:
>           * `x8r8g8b8` - 32-bit pixels, d[23:16]=r, d[15:8]=g, d[7:0]=b
>           * `x8b8g8r8` - 32-bit pixels, d[23:16]=b, d[15:8]=g, d[7:0]=r
>       enum:
> +      - mono
>         - a1r5g5b5
>         - a2r10g10b10
>         - a8b8g8r8

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)