Hello all, here is a first modification to provide the v4l2_extension module that does the clone device for a device driver. It does nearly nothing in fact, just creates a new device that clones the real device. - The first problem I encounter is in the video_open function, to call the open function of the base video driver. How to simulate the file opening for the base driver? This is mandatory to make the kernel create the private data for the base driver and use it in further calls.

In a second patch I will show you how a driver should use this extension for usbvision as an example, but can be easily be done for other drivers. - A good idea would be to have this registering procedure be done in videodev but as it is coded it is impossible (cyclic dependency between v4l2_extension and videodev).

Well, I am on vacation next week so I will not be able to respond to comments... be patient again :)

Cheers, Thierry --