[media] v4l2-ctrls: add control events

Whenever a control changes value or state an event is sent to anyone
that subscribed to it.

This functionality is useful for control panels but also for applications
that need to wait for (usually status) controls to change value.

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

1 files changed, 27 insertions, 2 deletions

diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index 8a4c309d2344..baafe2f2e02a 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -1791,6 +1791,7 @@ struct v4l2_streamparm {
 #define V4L2_EVENT_ALL                          0
 #define V4L2_EVENT_VSYNC                        1
 #define V4L2_EVENT_EOS                          2
+#define V4L2_EVENT_CTRL                         3
 #define V4L2_EVENT_PRIVATE_START                0x08000000
 
 /* Payload for V4L2_EVENT_VSYNC */
@@ -1799,21 +1800,45 @@ struct v4l2_event_vsync {
         __u8 field;
 } __attribute__ ((packed));
 
+/* Payload for V4L2_EVENT_CTRL */
+#define V4L2_EVENT_CTRL_CH_VALUE                (1 << 0)
+#define V4L2_EVENT_CTRL_CH_FLAGS                (1 << 1)
+
+struct v4l2_event_ctrl {
+        __u32 changes;
+        __u32 type;
+        union {
+                __s32 value;
+                __s64 value64;
+        };
+        __u32 flags;
+        __s32 minimum;
+        __s32 maximum;
+        __s32 step;
+        __s32 default_value;
+};
+
 struct v4l2_event {
         __u32                           type;
         union {
                 struct v4l2_event_vsync vsync;
+                struct v4l2_event_ctrl  ctrl;
                 __u8                    data[64];
         } u;
         __u32                           pending;
         __u32                           sequence;
         struct timespec                 timestamp;
-        __u32                           reserved[9];
+        __u32                           id;
+        __u32                           reserved[8];
 };
 
+#define V4L2_EVENT_SUB_FL_SEND_INITIAL (1 << 0)
+
 struct v4l2_event_subscription {
         __u32                           type;
-        __u32                           reserved[7];
+        __u32                           id;
+        __u32                           flags;
+        __u32                           reserved[5];
 };
 
 /*