[media] v4l: subdev: Events support

Provide v4l2_subdevs with v4l2_event support. Subdev drivers only need very
little to support events.

Signed-off-by: Sakari Ailus <[e-mail]>
Signed-off-by: David Cohen <[e-mail]>
Signed-off-by: Laurent Pinchart <[e-mail]>
Acked-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

Documentation/video4linux/v4l2-framework.txt

···
 	controls can be also be accessed through one (or several) V4L2 device
 	nodes.
 
+VIDIOC_DQEVENT
+VIDIOC_SUBSCRIBE_EVENT
+VIDIOC_UNSUBSCRIBE_EVENT
+
+	The events ioctls are identical to the ones defined in V4L2. They
+	behave identically, with the only exception that they deal only with
+	events generated by the sub-device. Depending on the driver, those
+	events can also be reported by one (or several) V4L2 device nodes.
+
+	Sub-device drivers that want to use events need to set the
+	V4L2_SUBDEV_USES_EVENTS v4l2_subdev::flags and initialize
+	v4l2_subdev::nevents to events queue depth before registering the
+	sub-device. After registration events can be queued as usual on the
+	v4l2_subdev::devnode device node.
+
+	To properly support events, the poll() file operation is also
+	implemented.
+
 
 I2C sub-device drivers
 ----------------------

drivers/media/video/v4l2-subdev.c

···
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
-#include <linux/types.h>
 #include <linux/ioctl.h>
+#include <linux/slab.h>
+#include <linux/types.h>
 #include <linux/videodev2.h>
 
 #include <media/v4l2-ctrls.h>
 #include <media/v4l2-device.h>
 #include <media/v4l2-ioctl.h>
+#include <media/v4l2-fh.h>
+#include <media/v4l2-event.h>
 
 static int subdev_open(struct file *file)
 {
+	struct video_device *vdev = video_devdata(file);
+	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
+	struct v4l2_fh *vfh;
+	int ret;
+
+	if (sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS) {
+		vfh = kzalloc(sizeof(*vfh), GFP_KERNEL);
+		if (vfh == NULL)
+			return -ENOMEM;
+
+		ret = v4l2_fh_init(vfh, vdev);
+		if (ret)
+			goto err;
+
+		ret = v4l2_event_init(vfh);
+		if (ret)
+			goto err;
+
+		ret = v4l2_event_alloc(vfh, sd->nevents);
+		if (ret)
+			goto err;
+
+		v4l2_fh_add(vfh);
+		file->private_data = vfh;
+	}
+
 	return 0;
+
+err:
+	if (vfh != NULL) {
+		v4l2_fh_exit(vfh);
+		kfree(vfh);
+	}
+
+	return ret;
 }
 
 static int subdev_close(struct file *file)
 {
+	struct v4l2_fh *vfh = file->private_data;
+
+	if (vfh != NULL) {
+		v4l2_fh_del(vfh);
+		v4l2_fh_exit(vfh);
+		kfree(vfh);
+	}
+
 	return 0;
 }
 
···
 {
 	struct video_device *vdev = video_devdata(file);
 	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
+	struct v4l2_fh *fh = file->private_data;
 
 	switch (cmd) {
 	case VIDIOC_QUERYCTRL:
···
 	case VIDIOC_TRY_EXT_CTRLS:
 		return v4l2_subdev_try_ext_ctrls(sd, arg);
 
+	case VIDIOC_DQEVENT:
+		if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
+			return -ENOIOCTLCMD;
+
+		return v4l2_event_dequeue(fh, arg, file->f_flags & O_NONBLOCK);
+
+	case VIDIOC_SUBSCRIBE_EVENT:
+		return v4l2_subdev_call(sd, core, subscribe_event, fh, arg);
+
+	case VIDIOC_UNSUBSCRIBE_EVENT:
+		return v4l2_subdev_call(sd, core, unsubscribe_event, fh, arg);
+
 	default:
 		return -ENOIOCTLCMD;
 	}
···
 	return video_usercopy(file, cmd, arg, subdev_do_ioctl);
 }
 
+static unsigned int subdev_poll(struct file *file, poll_table *wait)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
+	struct v4l2_fh *fh = file->private_data;
+
+	if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
+		return POLLERR;
+
+	poll_wait(file, &fh->events->wait, wait);
+
+	if (v4l2_event_pending(fh))
+		return POLLPRI;
+
+	return 0;
+}
+
 const struct v4l2_file_operations v4l2_subdev_fops = {
 	.owner = THIS_MODULE,
 	.open = subdev_open,
 	.unlocked_ioctl = subdev_ioctl,
 	.release = subdev_close,
+	.poll = subdev_poll,
 };
 
 void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)

include/media/v4l2-subdev.h

···
 
 struct v4l2_device;
 struct v4l2_ctrl_handler;
+struct v4l2_event_subscription;
+struct v4l2_fh;
 struct v4l2_subdev;
 struct tuner_setup;
 
···
 	int (*s_power)(struct v4l2_subdev *sd, int on);
 	int (*interrupt_service_routine)(struct v4l2_subdev *sd,
 						u32 status, bool *handled);
+	int (*subscribe_event)(struct v4l2_subdev *sd, struct v4l2_fh *fh,
+			       struct v4l2_event_subscription *sub);
+	int (*unsubscribe_event)(struct v4l2_subdev *sd, struct v4l2_fh *fh,
+				 struct v4l2_event_subscription *sub);
 };
 
 /* s_mode: switch the tuner to a specific tuner mode. Replacement of s_radio.
···
 #define V4L2_SUBDEV_FL_IS_SPI			(1U << 1)
 /* Set this flag if this subdev needs a device node. */
 #define V4L2_SUBDEV_FL_HAS_DEVNODE		(1U << 2)
+/* Set this flag if this subdev generates events. */
+#define V4L2_SUBDEV_FL_HAS_EVENTS		(1U << 3)
 
 /* Each instance of a subdev driver should create this struct, either
    stand-alone or embedded in a larger struct.
···
 	void *host_priv;
 	/* subdev device node */
 	struct video_device devnode;
+	/* number of events to be allocated on open */
+	unsigned int nevents;
 };
 
 #define vdev_to_v4l2_subdev(vdev) \