[media] v4l2-core: add code to check for specific ops

This patch adds a v4l2_subdev_has_op() macro and a v4l2_device_has_op macro to
quickly check if a specific subdev or any subdev supports a particular subdev
operation.
This makes it easy for drivers to disable certain ioctls if none of the subdevs
supports the necessary functionality.

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

2 files changed, 16 insertions, 0 deletions

diff --git a/include/media/v4l2-device.h b/include/media/v4l2-device.h
index d61febfb1668..c9b1593923f6 100644
--- a/include/media/v4l2-device.h
+++ b/include/media/v4l2-device.h
@@ -190,4 +190,17 @@ v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev);
                         ##args);                                        \
 })
 
+#define v4l2_device_has_op(v4l2_dev, o, f)                              \
+({                                                                      \
+        struct v4l2_subdev *__sd;                                       \
+        bool __result = false;                                          \
+        list_for_each_entry(__sd, &(v4l2_dev)->subdevs, list) {         \
+                if (v4l2_subdev_has_op(__sd, o, f)) {                   \
+                        __result = true;                                \
+                        break;                                          \
+                }                                                       \
+        }                                                               \
+        __result;                                                       \
+})
+
 #endif
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 8158a0810fdc..c42703a37602 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -687,4 +687,7 @@ void v4l2_subdev_init(struct v4l2_subdev *sd,
         ((!(sd) || !(sd)->v4l2_dev || !(sd)->v4l2_dev->notify) ? -ENODEV : \
          (sd)->v4l2_dev->notify((sd), (notification), (arg)))
 
+#define v4l2_subdev_has_op(sd, o, f) \
+        ((sd)->ops->o && (sd)->ops->o->f)
+
 #endif