[media] adv7842: Add support for control event notifications

Allow userspace applications to subscribe to control change events. This
can e.g. be used to monitor the 5V detect control to be notified when a
source is connected or disconnected.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/i2c/adv7842.c

@@ -40,6 +40,7 @@
 #include <linux/v4l2-dv-timings.h>
 #include <linux/hdmi.h>
 #include <media/v4l2-device.h>
+#include <media/v4l2-event.h>
 #include <media/v4l2-ctrls.h>
 #include <media/v4l2-dv-timings.h>
 #include <media/adv7842.h>
@@ -3015,6 +3016,8 @@ static const struct v4l2_subdev_core_ops adv7842_core_ops = {
 	.log_status = adv7842_log_status,
 	.ioctl = adv7842_ioctl,
 	.interrupt_service_routine = adv7842_isr,
+	.subscribe_event = v4l2_ctrl_subdev_subscribe_event,
+	.unsubscribe_event = v4l2_event_subdev_unsubscribe,
 #ifdef CONFIG_VIDEO_ADV_DEBUG
 	.g_register = adv7842_g_register,
 	.s_register = adv7842_s_register,
@@ -3210,7 +3213,7 @@ static int adv7842_probe(struct i2c_client *client,
 
 	sd = &state->sd;
 	v4l2_i2c_subdev_init(sd, client, &adv7842_ops);
-	sd->flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
+	sd->flags |= V4L2_SUBDEV_FL_HAS_DEVNODE | V4L2_SUBDEV_FL_HAS_EVENTS;
 	state->mode = pdata->mode;
 
 	state->hdmi_port_a = pdata->input == ADV7842_SELECT_HDMI_PORT_A;