[PATCH v3 8/8] drm: Introduce DRM_CLIENT_CAP_VIRTUALIZED_CURSOR_PLANE

[Zack Rusin]

From: Zack Rusin <zackr at 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_VIRTUALIZED_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 at vmware.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: dri-devel at lists.freedesktop.org
---
 drivers/gpu/drm/drm_ioctl.c |  9 +++++++++
 include/uapi/drm/drm.h      | 26 ++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 8e9afe7af19c..6fd17ff14656 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -361,6 +361,15 @@ 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_VIRTUALIZED_CURSOR_PLANE:
+		if (!drm_core_check_feature(dev, DRIVER_CURSOR_HOTSPOT))
+			return -EOPNOTSUPP;
+		if (!file_priv->atomic)
+			return -EINVAL;
+		if (req->value > 1)
+			return -EINVAL;
+		file_priv->supports_virtualized_cursor_plane = req->value;
+		break;
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index a87bbbbca2d4..057ef2a16d31 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -836,6 +836,32 @@ struct drm_get_cap {
  */
 #define DRM_CLIENT_CAP_WRITEBACK_CONNECTORS	5
 
+/**
+ * DRM_CLIENT_CAP_VIRTUALIZED_CURSOR_PLANE
+ *
+ * Drivers for para-virtualized hardware (e.g. vmwgfx, qxl, virtio and
+ * virtualbox) have additional restrictions for cursor planes (thus
+ * making cursor planes on those drivers not truly universal,) e.g.
+ * they need cursor planes to act like one would expect from a mouse
+ * cursor and have correctly set hotspot properties.
+ * If this client cap is not set the DRM core will hide cursor plane on
+ * those virtualized drivers because not setting it implies that the
+ * client is not capable of dealing with those extra restictions.
+ * Clients which do set cursor hotspot and treat the cursor plane
+ * like a mouse cursor should set this property.
+ * The client must enable &DRM_CLIENT_CAP_ATOMIC first.
+ *
+ * Setting this property on drivers which do not special case
+ * cursor planes (i.e. non-virtualized drivers) will return
+ * EOPNOTSUPP, which can be used by userspace to gauge
+ * requirements of the hardware/drivers they're running on.
+ *
+ * This capability is always supported for atomic-capable virtualized
+ * drivers starting from kernel version 6.5.
+ */
+#define DRM_CLIENT_CAP_VIRTUALIZED_CURSOR_PLANE	6
+
+
 /* DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
 struct drm_set_client_cap {
 	__u64 capability;
-- 
2.39.2