On Thursday, November 16th, 2023 at 13:06, Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > > + * Note that there are two types of damage handling: frame damage and buffer > > + * damage. The type of damage handling implemented depends on a driver's upload > > + * target. Drivers implementing a per-plane or per-CRTC upload target need to > > + * handle frame damage while drivers implementing a per-buffer upload target > > + * need to handle buffer damage. > > + * > > + * The existing damage helpers only support the frame damage type, there is no > > + * buffer age support or similar damage accumulation algorithm implemented yet. > > + * > > + * Only drivers handling frame damage can use the mentiored damage helpers to Typo: mentioned > > + * iterate over the damaged regions. Drivers that handle buffer damage, need to > > + * set &struct drm_plane_state.ignore_damage_clips as an indication to > > + * drm_atomic_helper_damage_iter_init() that the damage clips should be ignored. > > + * In that case, the returned damage rectangle is the &drm_plane_state.src since > > + * a full plane update should happen. > > + * > > + * For more information about the two type of damage, see: > > + * https://registry.khronos.org/EGL/extensions/KHR/EGL_KHR_swap_buffers_with_damage.txt > > + * https://emersion.fr/blog/2019/intro-to-damage-tracking/ > > One thought you might want to consider. > > These URLs are helpful. The only issue I have is that frame damage and > buffer damage are user-space concepts. The kernel bug is that damage > handling expects the backing storage/upload buffer not to change for a > given plane. If the upload buffer changes between page flips, the new > upload buffer has to be updated as a whole. Hence no damage handling then. Why would these concepts be specific to user-space? The kernel could better handle buffer damage instead of forcing full damage, by doing something similar to what user-space does. Anyways: Reviewed-by: Simon Ser <contact@xxxxxxxxxxx>
