[PATCH v2 8/8] drm: Introduce DRM_CLIENT_CAP_SUPPORTS_VIRTUAL_CURSOR_PLANE

[Zack Rusin <zack@kde.org>]

From: Zack Rusin <zackr@vmware.com>

Virtualized drivers place additional restrictions on the cursor plane
which breaks the contract of universal planes. To allow atomic
modesettings with virtualized drivers the clients need to advertise
that they're capable of dealing with those extra restrictions.

To do that introduce DRM_CLIENT_CAP_SUPPORTS_VIRTUAL_CURSOR_PLANE which
lets DRM know that the client is aware of and capable of dealing with
the extra restrictions on the virtual cursor plane.

Setting this option to true makes DRM expose the cursor plane on
virtualized drivers. The userspace is expected to set the hotspots
and handle mouse events on that plane.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/drm_ioctl.c |  9 +++++++++
 include/uapi/drm/drm.h      | 17 +++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 8faad23dc1d8..f10590b061d7 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -362,6 +362,15 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 			return -EINVAL;
 		file_priv->writeback_connectors = req->value;
 		break;
+	case DRM_CLIENT_CAP_SUPPORTS_VIRTUAL_CURSOR_PLANE:
+		if (!drm_core_check_feature(dev, DRIVER_VIRTUAL))
+			return -EOPNOTSUPP;
+		if (!file_priv->atomic)
+			return -EINVAL;
+		if (req->value > 1)
+			return -EINVAL;
+		file_priv->supports_virtual_cursor_plane = req->value;
+		break;
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 642808520d92..f24a1941abca 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -836,6 +836,23 @@ struct drm_get_cap {
  */
 #define DRM_CLIENT_CAP_WRITEBACK_CONNECTORS	5
 
+/**
+ * DRM_CLIENT_CAP_SUPPORTS_VIRTUAL_CURSOR_PLANE
+ *
+ * If set to 1, the DRM core will expose cursor plane to be used for
+ * virtualized mouse cursor, without virtualized drivers will not expose
+ * the cursor plane in atomic contexts. Cursor planes in virtualized
+ * drivers come with some additional restrictions and are not truly
+ * universal, e.g. they need to act like one would expect from a mouse
+ * cursor and have correctly set hotspot properties.
+ * The client must enable &DRM_CLIENT_CAP_ATOMIC first.
+ *
+ * This capability is always supported for atomic-capable virtualized drivers
+ * starting from kernel version 5.21.
+ */
+#define DRM_CLIENT_CAP_SUPPORTS_VIRTUAL_CURSOR_PLANE	6
+
+
 /* DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
 struct drm_set_client_cap {
 	__u64 capability;
-- 
2.34.1