| Message ID | 20250414085652.43904-1-contact@emersion.fr (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] drm/doc: document front-buffer rendering | expand |
On Mon, 14 Apr 2025 08:56:56 +0000 Simon Ser <contact@emersion.fr> wrote: > Explain how to perform front-buffer rendering. > > v2: apply Pekka's rewrite > > Signed-off-by: Simon Ser <contact@emersion.fr> > Cc: Pekka Paalanen <pekka.paalanen@collabora.com> > Cc: Simona Vetter <simona.vetter@ffwll.ch> > --- > drivers/gpu/drm/drm_blend.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c > index 6e74de833466..4e83f372ea51 100644 > --- a/drivers/gpu/drm/drm_blend.c > +++ b/drivers/gpu/drm/drm_blend.c > @@ -75,6 +75,12 @@ > * the currently visible vertical area of the &drm_crtc. > * FB_ID: > * Mode object ID of the &drm_framebuffer this plane should scan out. > + * > + * When a KMS client is perfoming front-buffer rendering, it should set > + * FB_ID to the same front-buffer FB on each atomic commit. This implies > + * to the driver that it needs to re-read the same FB again. Otherwise > + * drivers which do not employ continuously repeated scanout cycles might > + * not update the screen. > * CRTC_ID: > * Mode object ID of the &drm_crtc this plane should be connected to. > * Looking good, but given the new wording is 100% mine, not sure I can give reviewed-by? Co-authored-by maybe? Thanks, pq
On Mon, Apr 14, 2025 at 08:56:56AM +0000, Simon Ser wrote: > Explain how to perform front-buffer rendering. > > v2: apply Pekka's rewrite > > Signed-off-by: Simon Ser <contact@emersion.fr> > Cc: Pekka Paalanen <pekka.paalanen@collabora.com> > Cc: Simona Vetter <simona.vetter@ffwll.ch> > --- > drivers/gpu/drm/drm_blend.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c > index 6e74de833466..4e83f372ea51 100644 > --- a/drivers/gpu/drm/drm_blend.c > +++ b/drivers/gpu/drm/drm_blend.c > @@ -75,6 +75,12 @@ > * the currently visible vertical area of the &drm_crtc. > * FB_ID: > * Mode object ID of the &drm_framebuffer this plane should scan out. > + * > + * When a KMS client is perfoming front-buffer rendering, it should set > + * FB_ID to the same front-buffer FB on each atomic commit. This implies > + * to the driver that it needs to re-read the same FB again. Otherwise > + * drivers which do not employ continuously repeated scanout cycles might > + * not update the screen. Should probably add a caveat that this needs to be a sync commit/flip. The way the async flip was specified for atomic explicitly requires the driver to ignore the plane when the fb doesn't change. Also use dirtyfb instead if you don't want to get throttled to the vrefresh rate. Tthough I think with some drivers you might get throttled even with dirtyfb... > * CRTC_ID: > * Mode object ID of the &drm_crtc this plane should be connected to. > * > -- > 2.49.0 >
On Mon, Apr 14, 2025 at 04:28:55PM +0300, Ville Syrjälä wrote: > On Mon, Apr 14, 2025 at 08:56:56AM +0000, Simon Ser wrote: > > Explain how to perform front-buffer rendering. > > > > v2: apply Pekka's rewrite > > > > Signed-off-by: Simon Ser <contact@emersion.fr> > > Cc: Pekka Paalanen <pekka.paalanen@collabora.com> > > Cc: Simona Vetter <simona.vetter@ffwll.ch> > > --- > > drivers/gpu/drm/drm_blend.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c > > index 6e74de833466..4e83f372ea51 100644 > > --- a/drivers/gpu/drm/drm_blend.c > > +++ b/drivers/gpu/drm/drm_blend.c > > @@ -75,6 +75,12 @@ > > * the currently visible vertical area of the &drm_crtc. > > * FB_ID: > > * Mode object ID of the &drm_framebuffer this plane should scan out. > > + * > > + * When a KMS client is perfoming front-buffer rendering, it should set > > + * FB_ID to the same front-buffer FB on each atomic commit. This implies > > + * to the driver that it needs to re-read the same FB again. Otherwise > > + * drivers which do not employ continuously repeated scanout cycles might > > + * not update the screen. > > Should probably add a caveat that this needs to be a sync commit/flip. > The way the async flip was specified for atomic explicitly requires the > driver to ignore the plane when the fb doesn't change. > > Also use dirtyfb instead if you don't want to get throttled to the > vrefresh rate. Tthough I think with some drivers you might get > throttled even with dirtyfb... Half the userspace wants throttling, the other half wants it gone so glxgears looks better. I don't think you want to recommend the dirtyfb ioctl for that reason at all, because it's just a ymmv ioctl in what exactly you get in terms of blocking. It's funny. -Sima > > > * CRTC_ID: > > * Mode object ID of the &drm_crtc this plane should be connected to. > > * > > -- > > 2.49.0 > > > > -- > Ville Syrjälä > Intel
On Monday, April 14th, 2025 at 13:06, Pekka Paalanen <pekka.paalanen@collabora.com> wrote: > Looking good, but given the new wording is 100% mine, not sure I can > give reviewed-by? > > Co-authored-by maybe? Since it's 100% yours, probably you should be the commit author? Would you mind giving a S-o-b as well? But I wonder, would I be able to drop a R-b tag, meaning I agree with your new wording?
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c index 6e74de833466..4e83f372ea51 100644 --- a/drivers/gpu/drm/drm_blend.c +++ b/drivers/gpu/drm/drm_blend.c @@ -75,6 +75,12 @@ * the currently visible vertical area of the &drm_crtc. * FB_ID: * Mode object ID of the &drm_framebuffer this plane should scan out. + * + * When a KMS client is perfoming front-buffer rendering, it should set + * FB_ID to the same front-buffer FB on each atomic commit. This implies + * to the driver that it needs to re-read the same FB again. Otherwise + * drivers which do not employ continuously repeated scanout cycles might + * not update the screen. * CRTC_ID: * Mode object ID of the &drm_crtc this plane should be connected to. *
Explain how to perform front-buffer rendering. v2: apply Pekka's rewrite Signed-off-by: Simon Ser <contact@emersion.fr> Cc: Pekka Paalanen <pekka.paalanen@collabora.com> Cc: Simona Vetter <simona.vetter@ffwll.ch> --- drivers/gpu/drm/drm_blend.c | 6 ++++++ 1 file changed, 6 insertions(+)