V4L/DVB (9974): v4l2-dev: allow drivers to pass v4l2_device as parent

Drivers that use v4l2_device can set that as parent pointer in the v4l2_dev
field instead of using the struct device parent field.

This allows v4l2-dev.c to check whether this driver is v4l2_device based,
and if so then it can offer additional services.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/v4l2-dev.c

@@ -30,6 +30,7 @@
 #include <asm/system.h>
 
 #include <media/v4l2-common.h>
+#include <media/v4l2-device.h>
 
 #define VIDEO_NUM_DEVICES	256
 #define VIDEO_NAME              "video4linux"
@@ -407,6 +408,8 @@ int video_register_device_index(struct video_device *vdev, int type, int nr,
 
 	vdev->vfl_type = type;
 	vdev->cdev = NULL;
+	if (vdev->v4l2_dev)
+		vdev->parent = vdev->v4l2_dev->dev;
 
 	/* Part 2: find a free minor, kernel number and device index. */
 #ifdef CONFIG_VIDEO_FIXED_MINOR_RANGES

include/media/v4l2-dev.h

@@ -25,6 +25,7 @@
 #define VFL_TYPE_MAX		4
 
 struct v4l2_ioctl_callbacks;
+struct v4l2_device;
 
 /* Flag to mark the video_device struct as unregistered.
    Drivers can set this flag if they want to block all future
@@ -45,7 +46,10 @@ struct video_device
 	/* sysfs */
 	struct device dev;		/* v4l device */
 	struct cdev *cdev;		/* character device */
+
+	/* Set either parent or v4l2_dev if your driver uses v4l2_device */
 	struct device *parent;		/* device parent */
+	struct v4l2_device *v4l2_dev;	/* v4l2_device parent */
 
 	/* device info */
 	char name[32];