On Tue, 09 Apr 2024 15:25:26 +0200
Louis Chauvet <louis.chauvet@xxxxxxxxxxx> wrote:
> 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`.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/vkms/vkms_composer.c | 40 +++++++++++++++++-------------------
> 1 file changed, 19 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> index da0651a94c9b..45b111c74884 100644
> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> @@ -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);
>
Reviewed-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
Thanks,
pq
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