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>
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index e0d72d2..0a88d1d 100644
--- a/include/media/v4l2-dev.h
+++ b/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 @@
 	/* 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];