[PATCH libdrm 3/3] util: Add SMPTE pattern support for C4 format

[Ilia Mirkin]

On Mon, Mar 7, 2022 at 3:53 PM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> diff --git a/tests/util/pattern.c b/tests/util/pattern.c
> index 953bf95492ee150c..42d75d700700dc3d 100644
> --- a/tests/util/pattern.c
> +++ b/tests/util/pattern.c
> @@ -608,6 +608,46 @@ static void fill_smpte_rgb16fp(const struct util_rgb_info *rgb, void *mem,
>  static unsigned int smpte_middle[7] = { 6, 7, 4, 7, 2, 7, 0 };
>  static unsigned int smpte_bottom[8] = { 8, 9, 10, 7, 11, 7, 12, 7 };
>
> +static void write_pixel_4(uint8_t *mem, unsigned int x, unsigned int pixel)
> +{
> +       if (x & 1)
> +               mem[x / 2] = (mem[x / 2] & 0xf0) | (pixel & 0x0f);
> +       else
> +               mem[x / 2] = (mem[x / 2] & 0x0f) | (pixel << 4);
> +}

The standard layout is MSB? i.e. first pixel goes in the upper bits of
the first byte? It's been ages since I've dealt with C4 (or perhaps I
never even touched it), but this seems a bit surprising.