Unverified Commit cb6de83f authored by Louis Chauvet's avatar Louis Chauvet
Browse files

drm/vkms: Avoid computing blending limits inside pre_mul_alpha_blend 



The pre_mul_alpha_blend is dedicated to blending, so to avoid mixing
different concepts (coordinate calculation and color management), extract
the x_limit and x_dst computation outside of this helper.
It also increases the maintainability by grouping the computation related
to coordinates in the same place: the loop in `blend`.

Reviewed-by: default avatarPekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: default avatarJosé Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241118-yuv-v14-6-2dbc2f1e222c@bootlin.com


Signed-off-by: default avatarLouis Chauvet <louis.chauvet@bootlin.com>
parent d6dc39e4

drivers/gpu/drm/vkms/vkms_composer.c

+19 −21
Original line number Diff line number Diff line
@@ -24,34 +24,30 @@ static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha) 


/**

 * pre_mul_alpha_blend - alpha blending equation

 * @frame_info: Source framebuffer's metadata

 * @stage_buffer: The line with the pixels from src_plane

 * @output_buffer: A line buffer that receives all the blends output

 * @x_start: The start offset

 * @pixel_count: The number of pixels to blend

 *

 * Using the information from the `frame_info`, this blends only the

 * necessary pixels from the `stage_buffer` to the `output_buffer`

 * using premultiplied blend formula.

 * The pixels [0;@pixel_count) in stage_buffer are blended at [@x_start;@x_start+@pixel_count) in

 * output_buffer.

 *

 * The current DRM assumption is that pixel color values have been already

 * pre-multiplied with the alpha channel values. See more

 * drm_plane_create_blend_mode_property(). Also, this formula assumes a

 * completely opaque background.

 */

static void pre_mul_alpha_blend(struct vkms_frame_info *frame_info,

				struct line_buffer *stage_buffer,

				struct line_buffer *output_buffer)

static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,

				struct line_buffer *output_buffer, int x_start, int pixel_count)

{

	int x_dst = frame_info->dst.x1;

	struct pixel_argb_u16 *out = output_buffer->pixels + x_dst;

	struct pixel_argb_u16 *in = stage_buffer->pixels;

	int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst),

			    stage_buffer->n_pixels);



	for (int x = 0; x < x_limit; x++) {

		out[x].a = (u16)0xffff;

		out[x].r = pre_mul_blend_channel(in[x].r, out[x].r, in[x].a);

		out[x].g = pre_mul_blend_channel(in[x].g, out[x].g, in[x].a);

		out[x].b = pre_mul_blend_channel(in[x].b, out[x].b, in[x].a);

	struct pixel_argb_u16 *out = &output_buffer->pixels[x_start];

	const struct pixel_argb_u16 *in = stage_buffer->pixels;



	for (int i = 0; i < pixel_count; i++) {

		out[i].a = (u16)0xffff;

		out[i].r = pre_mul_blend_channel(in[i].r, out[i].r, in[i].a);

		out[i].g = pre_mul_blend_channel(in[i].g, out[i].g, in[i].a);

		out[i].b = pre_mul_blend_channel(in[i].b, out[i].b, in[i].a);

	}

}
@@ -183,7 +179,7 @@ static void blend(struct vkms_writeback_job *wb, 
{

	struct vkms_plane_state **plane = crtc_state->active_planes;

	u32 n_active_planes = crtc_state->num_active_planes;

	int y_pos;

	int y_pos, x_dst, pixel_count;



	const struct pixel_argb_u16 background_color = { .a = 0xffff };
@@ -201,14 +197,16 @@ static void blend(struct vkms_writeback_job *wb, 


		/* The active planes are composed associatively in z-order. */

		for (size_t i = 0; i < n_active_planes; i++) {

			x_dst = plane[i]->frame_info->dst.x1;

			pixel_count = min_t(int, drm_rect_width(&plane[i]->frame_info->dst),

					    (int)stage_buffer->n_pixels);

			y_pos = get_y_pos(plane[i]->frame_info, y);



			if (!check_limit(plane[i]->frame_info, y_pos))

				continue;



			vkms_compose_row(stage_buffer, plane[i], y_pos);

			pre_mul_alpha_blend(plane[i]->frame_info, stage_buffer,

					    output_buffer);

			pre_mul_alpha_blend(stage_buffer, output_buffer, x_dst, pixel_count);

		}



		apply_lut(crtc_state, output_buffer);