Re: [PATCH v3 3/9] drm/vkms: write/update the documentation for pixel conversion and pixel write functions

[Louis Chauvet]

Le 26/02/24 - 10:07, Arthur Grillo a écrit :
> 
> 
> 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 Update of outdated comments for pixel_write functions.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.

Is it better with this:

	/*
	 * 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
	 * buffer.
	 */
 
> Also, I think it's good to give more context, like:
> "The planes are composed line-by-line, instead of pixel-by-pixel"

And after PATCHv3 5/9:

	/*
	 * The planes are composed line-by-line to avoid heavy memory usage. It is a necessary
	 * complexity to avoid poor blending performance.
	 *
	 * The function pixel_read_line callback is used to read a line, using an efficient 
	 * algorithm for a specific format, into the staging buffer.
	 */

Kind regards,
Louis Chauvet

> Best Regards,
> ~Arthur Grillo

[...]

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