[PATCH] introduce __blkdev_driver_ioctl()

Analog of blkdev_driver_ioctl() with sane arguments.  For
now uses fake struct file, by the end of the series it won't
and blkdev_driver_ioctl() will become a wrapper around it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/blkdev.h

@@ -1074,6 +1074,8 @@ struct block_device_operations {
 	struct module *owner;
 };
 
+extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
+				 unsigned long);
 #else /* CONFIG_BLOCK */
 /*
  * stubs for when the block layer is configured out