[PATCH RFC libdrm 2/2] util: Fix 32 bpp patterns on big-endian

[Pekka Paalanen]

On Mon,  7 Mar 2022 21:53:42 +0100
Geert Uytterhoeven <geert at linux-m68k.org> wrote:

> DRM formats are defined to be little-endian, unless the
> DRM_FORMAT_BIG_ENDIAN flag is set.  Hence writes of multi-byte pixel
> values need to take endianness into account.
> 
> Introduce a cpu_to_le32() helper to convert 32-bit values from
> CPU-endian to little-endian, and use them in the various pattern fill
> functions for 32-bit formats.

Hi Geert,

FWIW, this explanation matches my understanding, so it sounds correct
to me. That's all I can say. I guess that means

Acked-by: Pekka Paalanen <pekka.paalanen at collabora.com>

?


Thanks,
pq

> 
> Signed-off-by: Geert Uytterhoeven <geert at linux-m68k.org>
> ---
> Works now with Linux' drm_fb_xrgb8888_to_rgb332_line(), which uses
> le32_to_cpu() to read pixel values from memory.
> 
> ---
>  tests/util/pattern.c | 30 +++++++++++++++++++++---------
>  1 file changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/tests/util/pattern.c b/tests/util/pattern.c
> index 42d75d700700dc3d..48677ea6d25b2676 100644
> --- a/tests/util/pattern.c
> +++ b/tests/util/pattern.c
> @@ -61,6 +61,18 @@ struct color_yuv {
>  	  .u = MAKE_YUV_601_U(r, g, b), \
>  	  .v = MAKE_YUV_601_V(r, g, b) }
>  
> +#if defined(__BIG_ENDIAN__) || defined(__sparc__) || defined(__mc68000__) || defined(__MIPSEB__)
> +static inline uint32_t cpu_to_le32(uint32_t x)
> +{
> +	return ((x & 0x000000ffU) << 24) |
> +	       ((x & 0x0000ff00U) <<  8) |
> +	       ((x & 0x00ff0000U) >>  8) |
> +	       ((x & 0xff000000U) >> 24);
> +}
> +#else
> +#define cpu_to_le32(x)	(x)
> +#endif

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