[PATCH v9 05/11] drm/fourcc: Add DRM_FORMAT_X403

[Simon Ser]

On Wednesday, March 25th, 2026 at 15:02, Tomi Valkeinen <tomi.valkeinen at ideasonboard.com> wrote:

> +/*
> + * 3 plane non-subsampled (444) YCbCr
> + * 10 bpc, 30 bits per sample image data in a single contiguous buffer.
> + * index 0: Y plane,  [31:0] x:Y2:Y1:Y0    [2:10:10:10] little endian
> + * index 1: Cb plane, [31:0] x:Cb2:Cb1:Cb0 [2:10:10:10] little endian
> + * index 2: Cr plane, [31:0] x:Cr2:Cr1:Cr0 [2:10:10:10] little endian
> + */
> +#define DRM_FORMAT_X403		fourcc_code('X', '4', '0', '3')

So, this one is different from the Q family, because Q has padding in
LSB rather than MSB. Speaking of, maybe we should add "LSB aligned" to
the doc comment to make that clear?

Re-reading the sibling thread about DRM_FORMAT_XV20, sounds like the
first digit matches my expectations for sub-sampling. How did you pick
the last two digits? I think I would've expected "30" here rather than
"03", since the last two planes are Cb Cr rather than Cr Cb.

Has the first "X" letter been picked arbitrarily? It's already used to
denote padding in other formats so I wonder if we should pick that
instead of, say, "T".

Simon