Re: [PATCH v8 03/17] drm/vkms: write/update the documentation for pixel conversion and pixel write functions

[Louis Chauvet]

Le 13/07/24 - 11:35, Maíra Canal a écrit :
> On 5/16/24 10:04, 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 Update of outdated comments for pixel_write functions.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>
> > Acked-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/vkms/vkms_composer.c |  7 ++++
> >   drivers/gpu/drm/vkms/vkms_drv.h      | 15 ++++++++-
> >   drivers/gpu/drm/vkms/vkms_formats.c  | 62 ++++++++++++++++++++++++++++++------
> >   3 files changed, 74 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> > index c6d9b4a65809..da0651a94c9b 100644
> > --- a/drivers/gpu/drm/vkms/vkms_composer.c
> > +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> > @@ -189,6 +189,13 @@ 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 to avoid heavy memory usage. It is a necessary
> > +	 * complexity to avoid poor blending performance.
> > +	 *
> > +	 * The function vkms_compose_row is used to read a line, pixel-by-pixel, into the staging
> 
> Nit: I know it's not kerneldoc, but I'd be glad if you use
> vkms_compose_row()
> 
> > +	 * buffer.
> > +	 */
> >   	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..212f4ab6a71f 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
> 
> s/structure/Structure
> 
> > + *
> > + * @fb: backing drm framebuffer
> > + * @src: source rectangle of this frame in the source framebuffer, stored in 16.16 fixed-point form
> > + * @dst: destination rectangle in the crtc buffer, stored in whole pixel units
> > + * @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;
> > @@ -49,9 +60,11 @@ struct vkms_writeback_job {
> >   };
> >   
> >   /**
> > - * vkms_plane_state - Driver specific plane state
> > + * struct 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
> 
> s/vkms_plane_state/struct vkms_plane_state
> 
> > + * ensure that this pointer is valid
> 
> Note: "If the @argument description has multiple lines, the continuation
> of the description should start at the same column as the previous
> line:" [1]
> 
> [1] https://docs.kernel.org/doc-guide/kernel-doc.html#function-parameters
> 
> >    */
> >   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 d597c48452ac..f157c43da4d6 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.c
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> > @@ -9,6 +9,18 @@
> >   
> >   #include "vkms_formats.h"
> >   
> > +/**
> > + * pixel_offset() - Get the offset of 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 ensure that the framebuffer associated with this request uses a pixel format
> > + * where block_h == block_w == 1.
> > + * If this requirement is not fulfilled, the resulting offset can point to an other pixel or
> > + * outside of the buffer.
> > + */
> >   static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y)
> >   {
> >   	struct drm_framebuffer *fb = frame_info->fb;
> > @@ -16,18 +28,22 @@ static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int
> >   	return fb->offsets[0] + (y * fb->pitches[0]) + (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.
> >    * This function assumes the channels are packed together, i.e. a color channel
> >    * comes immediately after another in the memory. And therefore, this function
> >    * doesn't work for YUV with chroma subsampling (e.g. YUV420 and NV21).
> > + *
> > + * The caller must ensure that the framebuffer associated with this request uses a pixel format
> > + * where block_h == block_w == 1, otherwise the returned pointer can be outside the buffer.
> >    */
> >   static void *packed_pixels_addr(const struct vkms_frame_info *frame_info,
> >   				int x, int y)
> > @@ -52,6 +68,13 @@ 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.
> 
> I believe it is @out_pixel.

Thanks for the review!

Yes it @out_pixel, I will fix those nits for the next iteration.

Thanks,
Louis Chauvet
 
> The content seems great to me, only those minor nits.
> 
> Best Regards,
> - Maíra
> 

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-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com