drm: add atomic properties

Once a driver is using atomic helpers for modeset, the next step is to
switch over to atomic properties.  To do this, make sure that any
modeset objects have their ->atomic_{get,set}_property() vfuncs suitably
populated if they have custom properties (you did already remember to
plug in atomic-helper func for the legacy ->set_property() vfuncs,
right?), and then set DRIVER_ATOMIC bit in driver_features flag.

A new cap is introduced, DRM_CLIENT_CAP_ATOMIC, for the purposes of
shielding legacy userspace from atomic properties.  Mostly for the
benefit of legacy DDX drivers that do silly things like getting/setting
each property at startup (since some of the new atomic properties will
be able to trigger modeset).

Signed-off-by: Rob Clark <robdclark@gmail.com>
[danvet: Squash in fixup patch to check for DRM_MODE_PROP_ATOMIC
instaed of the CAP define when filtering properties. Reported by
Tvrtko Uruslin, acked by Rob.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 9c4e149..ce3c681 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -521,6 +521,51 @@
 EXPORT_SYMBOL(drm_atomic_connector_get_property);
 
 /**
+ * drm_atomic_get_property - helper to read atomic property
+ * @obj: drm mode object whose property to read
+ * @property: the property to read
+ * @val: the read value, returned by reference
+ *
+ * RETURNS:
+ * Zero on success, error code on failure
+ */
+int drm_atomic_get_property(struct drm_mode_object *obj,
+		struct drm_property *property, uint64_t *val)
+{
+	struct drm_device *dev = property->dev;
+	int ret;
+
+	switch (obj->type) {
+	case DRM_MODE_OBJECT_CONNECTOR: {
+		struct drm_connector *connector = obj_to_connector(obj);
+		WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
+		ret = drm_atomic_connector_get_property(connector,
+				connector->state, property, val);
+		break;
+	}
+	case DRM_MODE_OBJECT_CRTC: {
+		struct drm_crtc *crtc = obj_to_crtc(obj);
+		WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
+		ret = drm_atomic_crtc_get_property(crtc,
+				crtc->state, property, val);
+		break;
+	}
+	case DRM_MODE_OBJECT_PLANE: {
+		struct drm_plane *plane = obj_to_plane(obj);
+		WARN_ON(!drm_modeset_is_locked(&plane->mutex));
+		ret = drm_atomic_plane_get_property(plane,
+				plane->state, property, val);
+		break;
+	}
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+/**
  * drm_atomic_set_crtc_for_plane - set crtc for plane
  * @plane_state: the plane whose incoming state to update
  * @crtc: crtc to use for the plane