[media] v4l2-ctrls: add a filter function to v4l2_ctrl_add_handler

With a filter function you can control more precisely which controls
are added. This is useful in particular for radio device nodes for
combined TV/Radio cards where you want to show just the radio-specific
controls and not controls like brightness.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index 6890f5e11ad0..801adb466bd2 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -384,14 +384,28 @@ struct v4l2_ctrl *v4l2_ctrl_add_ctrl(struct v4l2_ctrl_handler *hdl,
   * @hdl:       The control handler.
   * @add:       The control handler whose controls you want to add to
   *             the @hdl control handler.
+  * @filter:    This function will filter which controls should be added.
   *
-  * Does nothing if either of the two is a NULL pointer.
+  * Does nothing if either of the two handlers is a NULL pointer.
+  * If @filter is NULL, then all controls are added. Otherwise only those
+  * controls for which @filter returns true will be added.
   * In case of an error @hdl->error will be set to the error code (if it
   * wasn't set already).
   */
 int v4l2_ctrl_add_handler(struct v4l2_ctrl_handler *hdl,
-                          struct v4l2_ctrl_handler *add);
+                          struct v4l2_ctrl_handler *add,
+                          bool (*filter)(const struct v4l2_ctrl *ctrl));
 
+/** v4l2_ctrl_radio_filter() - Standard filter for radio controls.
+  * @ctrl:      The control that is filtered.
+  *
+  * This will return true for any controls that are valid for radio device
+  * nodes. Those are all of the V4L2_CID_AUDIO_* user controls and all FM
+  * transmitter class controls.
+  *
+  * This function is to be used with v4l2_ctrl_add_handler().
+  */
+bool v4l2_ctrl_radio_filter(const struct v4l2_ctrl *ctrl);
 
 /** v4l2_ctrl_cluster() - Mark all controls in the cluster as belonging to that cluster.
   * @ncontrols: The number of controls in this cluster.