drm: add atomic_get_property

Since we won't be using the obj->properties->values[] array to shadow
property values for atomic drivers, we are going to need a vfunc for
getting prop values.  Add that along w/ mandatory wrapper fxns.

v2: more comments and copypasta comment typo fix

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
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 6f729d1..9c4e149 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -243,6 +243,32 @@
 EXPORT_SYMBOL(drm_atomic_crtc_set_property);
 
 /**
+ * drm_atomic_crtc_get_property - get property on CRTC
+ * @crtc: the drm CRTC to get a property on
+ * @state: the state object with the property value to read
+ * @property: the property to get
+ * @val: the property value (returned by reference)
+ *
+ * Use this instead of calling crtc->atomic_get_property directly.
+ * This function handles generic/core properties and calls out to
+ * driver's ->atomic_get_property() for driver properties.  To ensure
+ * consistent behavior you must call this function rather than the
+ * driver hook directly.
+ *
+ * RETURNS:
+ * Zero on success, error code on failure
+ */
+int drm_atomic_crtc_get_property(struct drm_crtc *crtc,
+		const struct drm_crtc_state *state,
+		struct drm_property *property, uint64_t *val)
+{
+	if (crtc->funcs->atomic_get_property)
+		return crtc->funcs->atomic_get_property(crtc, state, property, val);
+	return -EINVAL;
+}
+EXPORT_SYMBOL(drm_atomic_crtc_get_property);
+
+/**
  * drm_atomic_get_plane_state - get plane state
  * @state: global atomic state object
  * @plane: plane to get state object for
@@ -324,6 +350,32 @@
 EXPORT_SYMBOL(drm_atomic_plane_set_property);
 
 /**
+ * drm_atomic_plane_get_property - get property on plane
+ * @plane: the drm plane to get a property on
+ * @state: the state object with the property value to read
+ * @property: the property to get
+ * @val: the property value (returned by reference)
+ *
+ * Use this instead of calling plane->atomic_get_property directly.
+ * This function handles generic/core properties and calls out to
+ * driver's ->atomic_get_property() for driver properties.  To ensure
+ * consistent behavior you must call this function rather than the
+ * driver hook directly.
+ *
+ * RETURNS:
+ * Zero on success, error code on failure
+ */
+int drm_atomic_plane_get_property(struct drm_plane *plane,
+		const struct drm_plane_state *state,
+		struct drm_property *property, uint64_t *val)
+{
+	if (plane->funcs->atomic_get_property)
+		return plane->funcs->atomic_get_property(plane, state, property, val);
+	return -EINVAL;
+}
+EXPORT_SYMBOL(drm_atomic_plane_get_property);
+
+/**
  * drm_atomic_get_connector_state - get connector state
  * @state: global atomic state object
  * @connector: connector to get state object for
@@ -433,6 +485,42 @@
 EXPORT_SYMBOL(drm_atomic_connector_set_property);
 
 /**
+ * drm_atomic_connector_get_property - get property on connector
+ * @connector: the drm connector to get a property on
+ * @state: the state object with the property value to read
+ * @property: the property to get
+ * @val: the property value (returned by reference)
+ *
+ * Use this instead of calling connector->atomic_get_property directly.
+ * This function handles generic/core properties and calls out to
+ * driver's ->atomic_get_property() for driver properties.  To ensure
+ * consistent behavior you must call this function rather than the
+ * driver hook directly.
+ *
+ * RETURNS:
+ * Zero on success, error code on failure
+ */
+int drm_atomic_connector_get_property(struct drm_connector *connector,
+		const struct drm_connector_state *state,
+		struct drm_property *property, uint64_t *val)
+{
+	struct drm_device *dev = connector->dev;
+	struct drm_mode_config *config = &dev->mode_config;
+
+	if (property == config->dpms_property) {
+		*val = connector->dpms;
+	} else if (connector->funcs->atomic_get_property) {
+		return connector->funcs->atomic_get_property(connector,
+				state, property, val);
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_connector_get_property);
+
+/**
  * 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