Hi Ulrik, On 06-03-16 14:50, Ulrik de Muelenaere wrote:
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.
Thanks for the patch-set overall I like it, one thing which worries is me is that sd_start_video and sd_start_depth may race, which is esp. problematic taking into account that both start/stop the depth stream (see the comment about this in sd_start_video()) this will require some coordination, so you like need to do something a bit more advanced and create a shared data struct somewhere for coordination (and with a lock in it). Likewise the v4l2 core is designed to have only one struct v4l2_device per struct device, so you need to modify probe2 to not call v4l2_device_register when it is called a second time for the same intf, and to make gspca_dev->vdev.v4l2_dev point to the v4l2_dev of the first gspca_dev registered. You will also need some changes for this in gspca_disconnect, as you will need to do all the calls on &gspca_dev->v4l2_dev only for the first registered device there, and you will need to do all the calls in gspca_release except for the v4l2_device_unregister() in a loop like you're using in disconnect. Note since you need a shared data struct anyways it might be easier to just use that (add some shared pointer to struct gspca_dev) for the array of gspca_devs rather then using the linked list, as for disconnect / release you will want to use the first registered gspca_dev to get the v4l2_dev address, and your linked approach gives you the last. Regards, Hans
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(-)
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