Lyude Paul wrote a very good intro to vblank here: https://lore.kernel.org/dri-devel/faf63d8a9ed23c16af69762f59d0dca6b2bf085f.camel@xxxxxxxxxx/T/#mce6480be738160e9d07c5d023e88fd78d7a06d27 Add this to the intro chapter in drm_vblank.c so others can benefit from it too. Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx> Co-developed-by: Lyude Paul <lyude@xxxxxxxxxx> Cc: Lyude Paul <lyude@xxxxxxxxxx> Cc: Daniel Vetter <daniel@xxxxxxxx> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> Cc: Maxime Ripard <mripard@xxxxxxxxxx> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> Cc: David Airlie <airlied@xxxxxxxx> --- drivers/gpu/drm/drm_vblank.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index bcf346b3e486..95cac22d59d1 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -41,6 +41,21 @@ /** * DOC: vblank handling * + * From the perspective of a computer, every time a computer monitor displays + * a new frame it's done by "scanning out" the display image from top to + * bottom, one row of pixels at a time. which row of pixels we're on is + * referred to as the scanline. + * Additionally, there's usually a couple of extra scanlines which we + * scan out, but aren't actually displayed on the screen (these sometimes + * get used by HDMI audio and friends, but that's another story). + * The period where we're on these scanlines is referred to as the vblank. + * + * On a lot of display hardware, programming needs to take effect during the + * vertical blanking period so that settings like gamma, what frame we're + * scanning out, etc. can be safely changed without showing visual tearing + * on the screen. In some unforgiving hardware, some of this programming has + * to both start and end in the same vblank - vertical blanking. + * * Vertical blanking plays a major role in graphics rendering. To achieve * tear-free display, users must synchronize page flips and/or rendering to * vertical blanking. The DRM API offers ioctls to perform page flips -- 2.20.1 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
