On Wed, 19 Aug 2020 17:53:36 -0300 Melissa Wen melissa.srw@gmail.com wrote:
The current VKMS blend function ignores alpha channel and just overwrites vaddr_src with vaddr_dst. This XRGB approach triggers a warning when running the kms_cursor_crc/cursor-alpha-transparent test case. In IGT tests, cairo_format_argb32 uses premultiplied alpha (according to documentation), so this patch considers premultiplied alpha colors to compose vaddr_src with vaddr_dst.
This change removes the following cursor-alpha-transparent warning: Suspicious CRC: All values are 0.
Cc: Daniel Vetter daniel@ffwll.ch Cc: Rodrigo Siqueira rodrigosiqueiramelo@gmail.com Cc: Haneen Mohammed hamohammed.sa@gmail.com
Signed-off-by: Melissa Wen melissa.srw@gmail.com
drivers/gpu/drm/vkms/vkms_composer.c | 43 +++++++++++++++++++++------- 1 file changed, 33 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c index 4f3b07a32b60..6aac962d3e2e 100644 --- a/drivers/gpu/drm/vkms/vkms_composer.c +++ b/drivers/gpu/drm/vkms/vkms_composer.c @@ -32,8 +32,6 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) src_offset = composer->offset + (i * composer->pitch) + (j * composer->cpp);
/* XRGB format ignores Alpha channel */bitmap_clear(vaddr_out + src_offset, 24, 8); crc = crc32_le(crc, vaddr_out + src_offset, sizeof(u32));@@ -42,6 +40,32 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) return crc; }
+u8 blend_channel(u8 c_src, u8 c_dst, u8 a_src) +{
- u32 pre_blend;
- u8 new_color;
- /* Premultiplied alpha blending - IGT + cairo context */
- pre_blend = (c_src * 255 + c_dst * (255 - a_src));
- /* Faster div by 255 */
- new_color = ((pre_blend + ((pre_blend + 257) >> 8)) >> 8);
- return new_color;
+}
+void alpha_blending(u8 *argb_src, u8 *argb_dst) +{
- u8 a_src;
- a_src = argb_src[3];
Hi,
DRM pixel formats are often defined as "bits in a 32-bit word", but here you are accessing it as an array of bytes. To me that looks suspicious wrt. big-endian architectures.
Unfortunately I have again forgot how DRM pixel formats should be interpreted on a big-endian machine, if I ever even understood it, so I can't say if this is right or not.
Thanks, pq
- argb_dst[0] = blend_channel(argb_src[0], argb_dst[0], a_src);
- argb_dst[1] = blend_channel(argb_src[1], argb_dst[1], a_src);
- argb_dst[2] = blend_channel(argb_src[2], argb_dst[2], a_src);
- /* Opaque primary */
- argb_dst[3] = 0xFF;
+}
/**
- blend - blend value at vaddr_src with value at vaddr_dst
- @vaddr_dst: destination address
@@ -50,12 +74,9 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer)
- @src_composer: source framebuffer's metadata
- Blend value at vaddr_src with value at vaddr_dst.
- Currently, this function write value of vaddr_src on value
- at vaddr_dst using buffer's metadata to locate the new values
- from vaddr_src and their destination at vaddr_dst.
- TODO: Use the alpha value to blend vaddr_src with vaddr_dst
instead of overwriting it.
- Currently, this function considers premultiplied alpha for blending, as used
- by Cairo. It uses buffer's metadata to locate the new composite values at
*/
- vaddr_dst.
static void blend(void *vaddr_dst, void *vaddr_src, struct vkms_composer *dest_composer, @@ -63,6 +84,7 @@ static void blend(void *vaddr_dst, void *vaddr_src, { int i, j, j_dst, i_dst; int offset_src, offset_dst;
u8 *p_dst, *p_src;
int x_src = src_composer->src.x1 >> 16; int y_src = src_composer->src.y1 >> 16;
@@ -84,8 +106,9 @@ static void blend(void *vaddr_dst, void *vaddr_src, + (i * src_composer->pitch) + (j * src_composer->cpp);
memcpy(vaddr_dst + offset_dst,vaddr_src + offset_src, sizeof(u32));
p_src = (u8 *)(vaddr_src + offset_src);p_dst = (u8 *)(vaddr_dst + offset_dst);alpha_blending(p_src, p_dst);