[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>

2 files changed, 25 insertions, 2 deletions

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index f40003550b60..631cdc0e0bda 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -1687,7 +1687,8 @@ EXPORT_SYMBOL(v4l2_ctrl_add_ctrl);
 
 /* Add the controls from another handler to our own. */
 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))
 {
         struct v4l2_ctrl_ref *ref;
         int ret = 0;
@@ -1707,6 +1708,9 @@ int v4l2_ctrl_add_handler(struct v4l2_ctrl_handler *hdl,
                 /* And control classes */
                 if (ctrl->type == V4L2_CTRL_TYPE_CTRL_CLASS)
                         continue;
+                /* Filter any unwanted controls */
+                if (filter && !filter(ctrl))
+                        continue;
                 ret = handler_new_ref(hdl, ctrl);
                 if (ret)
                         break;
@@ -1716,6 +1720,25 @@ int v4l2_ctrl_add_handler(struct v4l2_ctrl_handler *hdl,
 }
 EXPORT_SYMBOL(v4l2_ctrl_add_handler);
 
+bool v4l2_ctrl_radio_filter(const struct v4l2_ctrl *ctrl)
+{
+        if (V4L2_CTRL_ID2CLASS(ctrl->id) == V4L2_CTRL_CLASS_FM_TX)
+                return true;
+        switch (ctrl->id) {
+        case V4L2_CID_AUDIO_MUTE:
+        case V4L2_CID_AUDIO_VOLUME:
+        case V4L2_CID_AUDIO_BALANCE:
+        case V4L2_CID_AUDIO_BASS:
+        case V4L2_CID_AUDIO_TREBLE:
+        case V4L2_CID_AUDIO_LOUDNESS:
+                return true;
+        default:
+                break;
+        }
+        return false;
+}
+EXPORT_SYMBOL(v4l2_ctrl_radio_filter);
+
 /* Cluster controls */
 void v4l2_ctrl_cluster(unsigned ncontrols, struct v4l2_ctrl **controls)
 {
diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
index 1f203b85a637..513969fa695d 100644
--- a/drivers/media/v4l2-core/v4l2-device.c
+++ b/drivers/media/v4l2-core/v4l2-device.c
@@ -166,7 +166,7 @@ int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
         }
 
         /* This just returns 0 if either of the two args is NULL */
-        err = v4l2_ctrl_add_handler(v4l2_dev->ctrl_handler, sd->ctrl_handler);
+        err = v4l2_ctrl_add_handler(v4l2_dev->ctrl_handler, sd->ctrl_handler, NULL);
         if (err) {
                 if (sd->internal_ops && sd->internal_ops->unregistered)
                         sd->internal_ops->unregistered(sd);