[PATCH] videodev fixups / generic usercopy helper

Originally from Gerd...

I've just noticed that a hole left in the recent changes which should
allow the usb v4l drivers to unregister with open file handles.  The
drivers itself handle it just fine, but video_generic_ioctl() will barf
when called on unregistered devices.  Oops.

One way to fix this is to expect drivers call the helper function and
pass a pointer for the function doing the actual work, i.e. handle it
this way:

driver_ioctl(inode,file,cmd,userptr)
	-> video_usercopy(inode,file,cmd,userptr,func)
		copy_from_user(...)
		-> func(inode,file,cmd,kernelptr);
		copy_to_user(...)

Patch against 2.5.7-pre2 below. It updates videodev.[ch] and adapts
usbvideo.c to show how the driver changes will look like.

Note that this change makes the usercopy helper function a very generic
one, it probably could be used for other drivers to (as long as the API
has sane magic numbers based on _IO*(...) defines) as there is no
video4linux-related stuff in there any more.  So we might think of
renaming it an moving it to some more central place (fs/ioctl.c maybe).

1 files changed, 4 insertions, 4 deletions

diff --git a/include/linux/videodev.h b/include/linux/videodev.h
index 542e3ececef4..80966ed8e288 100644
--- a/include/linux/videodev.h
+++ b/include/linux/videodev.h
@@ -37,8 +37,6 @@ struct video_device
  	 * video_generic_ioctl() does the userspace copying of the
  	 * ioctl arguments */
  	struct file_operations *fops;
- 	int (*kernel_ioctl)(struct inode *inode, struct file *file,
- 			    unsigned int cmd, void *arg);
 	void *priv;		/* Used to be 'private' but that upsets C++ */
 
 	/* for videodev.c intenal usage -- don't touch */
@@ -60,8 +58,10 @@ extern struct video_device* video_devdata(struct file*);
 
 extern int video_exclusive_open(struct inode *inode, struct file *file);
 extern int video_exclusive_release(struct inode *inode, struct file *file);
-extern int video_generic_ioctl(struct inode *inode, struct file *file,
-			       unsigned int cmd, unsigned long arg);
+extern int video_usercopy(struct inode *inode, struct file *file,
+			  unsigned int cmd, unsigned long arg,
+			  int (*func)(struct inode *inode, struct file *file,
+				      unsigned int cmd, void *arg));
 #endif /* __KERNEL__ */
 
 #define VID_TYPE_CAPTURE	1	/* Can capture */