gspca_kinect: enable both video and depth streams

Hello,

The Kinect produces both a video and depth stream, but the current implementation of the gspca_kinect subdriver requires a depth_mode parameter at probe time to select one of the streams which will be exposed as a v4l device. This patchset allows both streams to be accessed as separate video nodes.

A possible solution which has been discussed in the past is to call gspca_dev_probe() multiple times in order to create multiple video nodes. See the following mails:

http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/26194/focus=26213
http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/76715/focus=78344

In the second mail linked above, it was mentioned that gspca_dev_probe() cannot be called multiple times for the same USB interface, since gspca_dev_probe2() stores a pointer to the new gspca_dev as the interface's private data. This is required for gspca_disconnect(), gspca_suspend() and gspca_resume(). As far as I can tell, this is the only reason gspca_dev_probe() cannot be called multiple times.

The first patch fixes this by storing other devices linked to the same interface as a linked list. The second patch then calls gspca_dev_probe() twice in the gspca_kinect subdriver, to create a video node for each stream.

Some notes on error handling, which I think should be reviewed:

* I could not test the gspca_suspend() and gspca_resume() functions. From my evaluation of the code, it seems that the only effect of returning an error code from gspca_resume() is that a message is logged. Therefore I decided to attempt to resume each gspca_dev when the interface is resumed, even if one fails. Bitwise OR seems like the best way to combine potentially multiple error codes.

* In the gspca_kinect subdriver, if the second call to gspca_dev_probe() fails, the first video node will still be available. I handle this case by calling gspca_disconnect(), which worked when I was testing, but I am not sure if this is the correct way to handle it.

Regards,
Ulrik

Ulrik de Muelenaere (2):
[media] gspca: allow multiple probes per USB interface [media] gspca_kinect: enable both video and depth streams

 drivers/media/usb/gspca/gspca.c  | 129 +++++++++++++++++++++++----------------
 drivers/media/usb/gspca/gspca.h  |   1 +
 drivers/media/usb/gspca/kinect.c |  28 +++++----
 3 files changed, 91 insertions(+), 67 deletions(-)

2.7.0