Den 08.07.2022 20.21, skrev Geert Uytterhoeven:
> DRM formats are defined to be little-endian, unless the
> DRM_FORMAT_BIG_ENDIAN flag is set. Hence when converting from one
> format to another, multi-byte pixel values loaded from memory must be
> converted from little-endian to host-endian. Conversely, multi-byte
> pixel values written to memory must be converted from host-endian to
> little-endian. Currently only drm_fb_xrgb8888_to_rgb332_line() includes
> endianness handling.
>
> Fix gud_xrgb8888_to_color() on big-endian platforms by adding the
> missing endianness handling.
>
> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> ---
> Compile-tested only.
>
> Interestingly, drm_fb_xrgb8888_to_rgb332() was introduced for GUD,
> and always had correct endiannes handling...
RGB332 support was added later and by that time I had understood that
the framebuffer was little endian and not host endian as I first assumed
(there's a fixme comment in gud_pipe.c that BE is probably broken but I
haven't got any hw to test on so I haven't tried to fix it).
Thanks for fixing this, pathces 2 and 3 tested on drm/gud and applied to
drm-misc-next.
Noralf.
> ---
> drivers/gpu/drm/gud/gud_pipe.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> index 4873f9799f412e04..d42592f6daab8b2a 100644
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -105,7 +105,8 @@ static size_t gud_xrgb8888_to_color(u8 *dst, const struct drm_format_info *forma
> unsigned int bits_per_pixel = 8 / block_width;
> u8 r, g, b, pix, *block = dst; /* Assign to silence compiler warning */
> unsigned int x, y, width;
> - u32 *pix32;
> + __le32 *sbuf32;
> + u32 pix32;
> size_t len;
>
> /* Start on a byte boundary */
> @@ -114,8 +115,8 @@ static size_t gud_xrgb8888_to_color(u8 *dst, const struct drm_format_info *forma
> len = drm_format_info_min_pitch(format, 0, width) * drm_rect_height(rect);
>
> for (y = rect->y1; y < rect->y2; y++) {
> - pix32 = src + (y * fb->pitches[0]);
> - pix32 += rect->x1;
> + sbuf32 = src + (y * fb->pitches[0]);
> + sbuf32 += rect->x1;
>
> for (x = 0; x < width; x++) {
> unsigned int pixpos = x % block_width; /* within byte from the left */
> @@ -126,9 +127,10 @@ static size_t gud_xrgb8888_to_color(u8 *dst, const struct drm_format_info *forma
> *block = 0;
> }
>
> - r = *pix32 >> 16;
> - g = *pix32 >> 8;
> - b = *pix32++;
> + pix32 = le32_to_cpu(*sbuf32++);
> + r = pix32 >> 16;
> + g = pix32 >> 8;
> + b = pix32;
>
> switch (format->format) {
> case GUD_DRM_FORMAT_XRGB1111:
