On Wed, Feb 28, 2024 at 10:12:28AM +0000, Simon Ser wrote: > On Tuesday, February 27th, 2024 at 20:35, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > > > Add a new immutable plane property by which a plane can advertise > > a handful of recommended plane sizes. This would be mostly exposed > > by cursor planes as a slightly more capable replacement for > > the DRM_CAP_CURSOR_WIDTH/HEIGHT caps, which can only declare > > a one size fits all limit for the whole device. > > > > Currently eg. amdgpu/i915/nouveau just advertize the max cursor > > size via the cursor size caps. But always using the max sized > > cursor can waste a surprising amount of power, so a better > > stragey is desirable. > > Typo: strategy > > > Most other drivers don't specify any cursor size at all, in > > which case the ioctl code just claims that 64x64 is a great > > choice. Whether that is actually true is debatable. > > > > A poll of various compositor developers informs us that > > blindly probing with setcursor/atomic ioctl to determine > > suitable cursor sizes is not acceptable, thus the > > introduction of the new property to supplant the cursor > > size caps. The compositor will now be free to select a > > more optimal cursor size from the short list of options. > > > > Note that the reported sizes (either via the property or the > > caps) make no claims about things such as plane scaling. So > > these things should only really be consulted for simple > > "cursor like" use cases. > > > > Userspace consumer in the form of mutter seems ready: > > https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3165 > > Do we need an IGT as well to merge this new uAPI? At least for i915 the current igts already cover a superset of what the property reports. But I guess we could add another test that explicitly tests the sizes reported by the hint as well, if not already covered by other tests. > > > v2: Try to add some docs > > v3: Specify that value 0 is reserved for future use (basic idea from Jonas) > > Drop the note about typical hardware (Pekka) > > v4: Update the docs to indicate the list is "in order of preference" > > Add a a link to the mutter MR > > > > Cc: Simon Ser <contact@xxxxxxxxxxx> > > Cc: Jonas Ådahl <jadahl@xxxxxxxxxx> > > Cc: Daniel Stone <daniel@xxxxxxxxxxxxx> > > Cc: Sameer Lattannavar <sameer.lattannavar@xxxxxxxxx> > > Cc: Sebastian Wick <sebastian.wick@xxxxxxxxxx> > > Acked-by: Harry Wentland <harry.wentland@xxxxxxx> > > Acked-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx> > > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > --- > > drivers/gpu/drm/drm_mode_config.c | 7 +++++ > > drivers/gpu/drm/drm_plane.c | 52 +++++++++++++++++++++++++++++++ > > include/drm/drm_mode_config.h | 5 +++ > > include/drm/drm_plane.h | 4 +++ > > include/uapi/drm/drm_mode.h | 11 +++++++ > > 5 files changed, 79 insertions(+) > > > > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c > > index 48fd2d67f352..568972258222 100644 > > --- a/drivers/gpu/drm/drm_mode_config.c > > +++ b/drivers/gpu/drm/drm_mode_config.c > > @@ -372,6 +372,13 @@ static int drm_mode_create_standard_properties(struct drm_device *dev) > > return -ENOMEM; > > dev->mode_config.modifiers_property = prop; > > > > + prop = drm_property_create(dev, > > + DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_BLOB, > > + "SIZE_HINTS", 0); > > + if (!prop) > > + return -ENOMEM; > > + dev->mode_config.size_hints_property = prop; > > + > > return 0; > > } > > > > diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c > > index 672c655c7a8e..4135ce16e608 100644 > > --- a/drivers/gpu/drm/drm_plane.c > > +++ b/drivers/gpu/drm/drm_plane.c > > @@ -140,6 +140,25 @@ > > * DRM_FORMAT_MOD_LINEAR. Before linux kernel release v5.1 there have been > > * various bugs in this area with inconsistencies between the capability > > * flag and per-plane properties. > > + * > > + * SIZE_HINTS: > > + * Blob property which contains the set of recommended plane size > > + * which can used for simple "cursor like" use cases (eg. no scaling). > > + * Using these hints frees userspace from extensive probing of > > + * supported plane sizes through atomic/setcursor ioctls. > > + * > > + * The blob contains an array of struct drm_plane_size_hint, in > > + * order of preference. For optimal usage userspace should pick > > + * the first size that satisfies its own requirements. > > + * > > + * Drivers should only attach this property to planes that > > + * support a very limited set of sizes. > > + * > > + * Note that property value 0 (ie. no blob) is reserved for potential > > + * future use. Current userspace is expected to ignore the property > > + * if the value is 0, and fall back to some other means (eg. > > + * &DRM_CAP_CURSOR_WIDTH and &DRM_CAP_CURSOR_HEIGHT) to determine > > + * the appropriate plane size to use. > > */ > > > > static unsigned int drm_num_planes(struct drm_device *dev) > > @@ -1729,3 +1748,36 @@ int drm_plane_create_scaling_filter_property(struct drm_plane *plane, > > return 0; > > } > > EXPORT_SYMBOL(drm_plane_create_scaling_filter_property); > > + > > +/** > > + * drm_plane_add_size_hint_property - create a size hint property > > + * > > + * @plane: drm plane > > + * @hints: size hints > > + * @num_hints: number of size hints > > + * > > + * Create a size hints property for the plane. > > + * > > + * RETURNS: > > + * Zero for success or -errno > > + */ > > +int drm_plane_add_size_hints_property(struct drm_plane *plane, > > + const struct drm_plane_size_hint *hints, > > + int num_hints) > > +{ > > Can we add a plane type check here, to make sure this is only attached to > cursor planes? If there is a use-case for other plane types, I'd prefer to > discuss about it first before expanding the property's scope. Sure. I don't have a specific usecase for other plane types right now. But I could imagine some hardware having multiple fixed/limited size planes. Not sure if there are assumptions in userspace regarding the number of cursor planes per-crtc, so not sure all such planes can be declared as cursors. > > With that: > Reviewed-by: Simon Ser <contact@xxxxxxxxxxx> > > > + struct drm_device *dev = plane->dev; > > + struct drm_mode_config *config = &dev->mode_config; > > + struct drm_property_blob *blob; > > + > > + blob = drm_property_create_blob(dev, > > + array_size(sizeof(hints[0]), num_hints), > > + hints); > > + if (IS_ERR(blob)) > > + return PTR_ERR(blob); > > + > > + drm_object_attach_property(&plane->base, config->size_hints_property, > > + blob->base.id); > > + > > + return 0; > > +} > > +EXPORT_SYMBOL(drm_plane_add_size_hints_property); -- Ville Syrjälä Intel
