On Mon, 7 Mar 2022 21:53:42 +0100 Geert Uytterhoeven geert@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@collabora.com
?
Thanks, pq
Signed-off-by: Geert Uytterhoeven geert@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