drm: Add a SET_CLIENT_CAP ioctl

This ioctl can be used to turn some knobs in a DRM driver. The client
can ask the DRM core for an alternate view of the reality: it can be
useful to be able to instruct the core that the DRM client can handle
new functionnality that would otherwise break current ABI.

v2: Rename to ioctl from SET_CAP to SET_CLIENT_CAP (Chris Wilson)
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_drv.c

@@ -69,6 +69,7 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 	DRM_IOCTL_DEF(DRM_IOCTL_GET_CLIENT, drm_getclient, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_GET_STATS, drm_getstats, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_GET_CAP, drm_getcap, DRM_UNLOCKED|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF(DRM_IOCTL_SET_CLIENT_CAP, drm_setclientcap, 0),
 	DRM_IOCTL_DEF(DRM_IOCTL_SET_VERSION, drm_setversion, DRM_MASTER),
 
 	DRM_IOCTL_DEF(DRM_IOCTL_SET_UNIQUE, drm_setunique, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY),

drivers/gpu/drm/drm_ioctl.c

@@ -302,6 +302,15 @@ int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 	return 0;
 }
 
+/**
+ * Set device/driver capabilities
+ */
+int
+drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
+{
+	return -EINVAL;
+}
+
 /**
  * Setversion ioctl.
  *

include/drm/drmP.h

@@ -1303,6 +1303,8 @@ extern int drm_getstats(struct drm_device *dev, void *data,
 			struct drm_file *file_priv);
 extern int drm_getcap(struct drm_device *dev, void *data,
 		      struct drm_file *file_priv);
+extern int drm_setclientcap(struct drm_device *dev, void *data,
+			    struct drm_file *file_priv);
 extern int drm_setversion(struct drm_device *dev, void *data,
 			  struct drm_file *file_priv);
 extern int drm_noop(struct drm_device *dev, void *data,

include/uapi/drm/drm.h

@@ -627,6 +627,12 @@ struct drm_get_cap {
 	__u64 value;
 };
 
+/** DRM_IOCTL_SET_CLIENT_CAP ioctl argument type */
+struct drm_set_client_cap {
+	__u64 capability;
+	__u64 value;
+};
+
 #define DRM_CLOEXEC O_CLOEXEC
 struct drm_prime_handle {
 	__u32 handle;
@@ -659,6 +665,7 @@ struct drm_prime_handle {
 #define DRM_IOCTL_GEM_FLINK		DRM_IOWR(0x0a, struct drm_gem_flink)
 #define DRM_IOCTL_GEM_OPEN		DRM_IOWR(0x0b, struct drm_gem_open)
 #define DRM_IOCTL_GET_CAP		DRM_IOWR(0x0c, struct drm_get_cap)
+#define DRM_IOCTL_SET_CLIENT_CAP	DRM_IOW( 0x0d, struct drm_set_client_cap)
 
 #define DRM_IOCTL_SET_UNIQUE		DRM_IOW( 0x10, struct drm_unique)
 #define DRM_IOCTL_AUTH_MAGIC		DRM_IOW( 0x11, struct drm_auth)