diff options
| -rw-r--r-- | Documentation/gpu/drm-kms.rst | 6 | ||||
| -rw-r--r-- | drivers/gpu/drm/drm_plane.c | 58 |
2 files changed, 63 insertions, 1 deletions
diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst index 270d320407c7..4a112b8cc7fb 100644 --- a/Documentation/gpu/drm-kms.rst +++ b/Documentation/gpu/drm-kms.rst @@ -579,6 +579,12 @@ Variable Refresh Properties .. kernel-doc:: drivers/gpu/drm/drm_connector.c :doc: Variable refresh properties +Cursor Hotspot Properties +--------------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_plane.c + :doc: hotspot properties + Existing KMS Properties ----------------------- diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index 1dc00ad4c33c..f3f2eae83cca 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -231,13 +231,69 @@ static int create_in_format_blob(struct drm_device *dev, struct drm_plane *plane } /** + * DOC: hotspot properties + * + * HOTSPOT_X: property to set mouse hotspot x offset. + * HOTSPOT_Y: property to set mouse hotspot y offset. + * + * When the plane is being used as a cursor image to display a mouse pointer, + * the "hotspot" is the offset within the cursor image where mouse events + * are expected to go. + * + * Positive values move the hotspot from the top-left corner of the cursor + * plane towards the right and bottom. + * + * Most display drivers do not need this information because the + * hotspot is not actually connected to anything visible on screen. + * However, this is necessary for display drivers like the para-virtualized + * drivers (eg qxl, vbox, virtio, vmwgfx), that are attached to a user console + * with a mouse pointer. Since these consoles are often being remoted over a + * network, they would otherwise have to wait to display the pointer movement to + * the user until a full network round-trip has occurred. New mouse events have + * to be sent from the user's console, over the network to the virtual input + * devices, forwarded to the desktop for processing, and then the cursor plane's + * position can be updated and sent back to the user's console over the network. + * Instead, with the hotspot information, the console can anticipate the new + * location, and draw the mouse cursor there before the confirmation comes in. + * To do that correctly, the user's console must be able predict how the + * desktop will process mouse events, which normally requires the desktop's + * mouse topology information, ie where each CRTC sits in the mouse coordinate + * space. This is typically sent to the para-virtualized drivers using some + * driver-specific method, and the driver then forwards it to the console by + * way of the virtual display device or hypervisor. + * + * The assumption is generally made that there is only one cursor plane being + * used this way at a time, and that the desktop is feeding all mouse devices + * into the same global pointer. Para-virtualized drivers that require this + * should only be exposing a single cursor plane, or find some other way + * to coordinate with a userspace desktop that supports multiple pointers. + * If the hotspot properties are set, the cursor plane is therefore assumed to be + * used only for displaying a mouse cursor image, and the position of the combined + * cursor plane + offset can therefore be used for coordinating with input from a + * mouse device. + * + * The cursor will then be drawn either at the location of the plane in the CRTC + * console, or as a free-floating cursor plane on the user's console + * corresponding to their desktop mouse position. + * + * DRM clients which would like to work correctly on drivers which expose + * hotspot properties should advertise DRM_CLIENT_CAP_CURSOR_PLANE_HOTSPOT. + * Setting this property on drivers which do not special case + * cursor planes will return EOPNOTSUPP, which can be used by userspace to + * gauge requirements of the hardware/drivers they're running on. Advertising + * DRM_CLIENT_CAP_CURSOR_PLANE_HOTSPOT implies that the userspace client will be + * correctly setting the hotspot properties. + */ + +/** * drm_plane_create_hotspot_properties - creates the mouse hotspot * properties and attaches them to the given cursor plane * * @plane: drm cursor plane * * This function enables the mouse hotspot property on a given - * cursor plane. + * cursor plane. Look at the documentation for hotspot properties + * to get a better understanding for what they're used for. * * RETURNS: * Zero for success or -errno |