On 26/02/24 05:46, Louis Chauvet wrote:
> Add some documentation on pixel conversion functions.
> Update of outdated comments for pixel_write functions.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/vkms/vkms_composer.c | 4 +++
> drivers/gpu/drm/vkms/vkms_drv.h | 13 ++++++++
> drivers/gpu/drm/vkms/vkms_formats.c | 58 ++++++++++++++++++++++++++++++------
> 3 files changed, 66 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> index c6d9b4a65809..5b341222d239 100644
> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> @@ -189,6 +189,10 @@ static void blend(struct vkms_writeback_job *wb,
>
> size_t crtc_y_limit = crtc_state->base.crtc->mode.vdisplay;
>
> + /*
> + * The planes are composed line-by-line. It is a necessary complexity to avoid poor
> + * blending performance.
At this moment in the series, you have not yet reintroduced the
line-by-line algorithm yet. Maybe it's better to add this comment when
you do.
Also, I think it's good to give more context, like:
"The planes are composed line-by-line, instead of pixel-by-pixel"
Best Regards,
~Arthur Grillo
> + */
> for (size_t y = 0; y < crtc_y_limit; y++) {
> fill_background(&background_color, output_buffer);
>
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index b4b357447292..18086423a3a7 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -25,6 +25,17 @@
>
> #define VKMS_LUT_SIZE 256
>
> +/**
> + * struct vkms_frame_info - structure to store the state of a frame
> + *
> + * @fb: backing drm framebuffer
> + * @src: source rectangle of this frame in the source framebuffer
> + * @dst: destination rectangle in the crtc buffer
> + * @map: see drm_shadow_plane_state@data
> + * @rotation: rotation applied to the source.
> + *
> + * @src and @dst should have the same size modulo the rotation.
> + */
> struct vkms_frame_info {
> struct drm_framebuffer *fb;
> struct drm_rect src, dst;
> @@ -52,6 +63,8 @@ struct vkms_writeback_job {
> * vkms_plane_state - Driver specific plane state
> * @base: base plane state
> * @frame_info: data required for composing computation
> + * @pixel_read: function to read a pixel in this plane. The creator of a vkms_plane_state must
> + * ensure that this pointer is valid
> */
> struct vkms_plane_state {
> struct drm_shadow_plane_state base;
> diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
> index 172830a3936a..cb7a49b7c8e7 100644
> --- a/drivers/gpu/drm/vkms/vkms_formats.c
> +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> @@ -9,6 +9,17 @@
>
> #include "vkms_formats.h"
>
> +/**
> + * packed_pixels_offset() - Get the offset of the block containing the pixel at coordinates x/y
> + * in the first plane
> + *
> + * @frame_info: Buffer metadata
> + * @x: The x coordinate of the wanted pixel in the buffer
> + * @y: The y coordinate of the wanted pixel in the buffer
> + *
> + * The caller must be aware that this offset is not always a pointer to a pixel. If individual
> + * pixel values are needed, they have to be extracted from the resulting block.
> + */
> static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y)
> {
> struct drm_framebuffer *fb = frame_info->fb;
> @@ -17,12 +28,13 @@ static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int
> + (x * fb->format->cpp[0]);
> }
>
> -/*
> - * packed_pixels_addr - Get the pointer to pixel of a given pair of coordinates
> +/**
> + * packed_pixels_addr() - Get the pointer to the block containing the pixel at the given
> + * coordinates
> *
> * @frame_info: Buffer metadata
> - * @x: The x(width) coordinate of the 2D buffer
> - * @y: The y(Heigth) coordinate of the 2D buffer
> + * @x: The x(width) coordinate inside the plane
> + * @y: The y(height) coordinate inside the plane
> *
> * Takes the information stored in the frame_info, a pair of coordinates, and
> * returns the address of the first color channel.
> @@ -53,6 +65,13 @@ static int get_x_position(const struct vkms_frame_info *frame_info, int limit, i
> return x;
> }
>
> +/*
> + * The following functions take pixel data from the buffer and convert them to the format
> + * ARGB16161616 in out_pixel.
> + *
> + * They are used in the `vkms_compose_row` function to handle multiple formats.
> + */
> +
> static void ARGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
> {
> /*
> @@ -145,12 +164,11 @@ void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state
> }
>
> /*
> - * The following functions take an line of argb_u16 pixels from the
> - * src_buffer, convert them to a specific format, and store them in the
> - * destination.
> + * The following functions take one argb_u16 pixel and convert it to a specific format. The
> + * result is stored in @dst_pixels.
> *
> - * They are used in the `compose_active_planes` to convert and store a line
> - * from the src_buffer to the writeback buffer.
> + * They are used in the `vkms_writeback_row` to convert and store a pixel from the src_buffer to
> + * the writeback buffer.
> */
> static void argb_u16_to_ARGB8888(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> {
> @@ -216,6 +234,14 @@ static void argb_u16_to_RGB565(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> *pixels = cpu_to_le16(r << 11 | g << 5 | b);
> }
>
> +/**
> + * Generic loop for all supported writeback format. It is executed just after the blending to
> + * write a line in the writeback buffer.
> + *
> + * @wb: Job where to insert the final image
> + * @src_buffer: Line to write
> + * @y: Row to write in the writeback buffer
> + */
> void vkms_writeback_row(struct vkms_writeback_job *wb,
> const struct line_buffer *src_buffer, int y)
> {
> @@ -229,6 +255,13 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
> wb->pixel_write(dst_pixels, &in_pixels[x]);
> }
>
> +/**
> + * Retrieve the correct read_pixel function for a specific format.
> + * The returned pointer is NULL for unsupported pixel formats. The caller must ensure that the
> + * pointer is valid before using it in a vkms_plane_state.
> + *
> + * @format: 4cc of the format
> + */
> void *get_pixel_conversion_function(u32 format)
> {
> switch (format) {
> @@ -247,6 +280,13 @@ void *get_pixel_conversion_function(u32 format)
> }
> }
>
> +/**
> + * Retrieve the correct write_pixel function for a specific format.
> + * The returned pointer is NULL for unsupported pixel formats. The caller must ensure that the
> + * pointer is valid before using it in a vkms_writeback_job.
> + *
> + * @format: 4cc of the format
> + */
> void *get_pixel_write_function(u32 format)
> {
> switch (format) {
>
