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314b3e0881
Currently gspca supported usb-1.1 webcams for which we support the input button through an interrupt endpoint won't stream (not enough bandwidth error) when used through an USB-2.0 hub. After much debugging I've found out that the cause for this is that the ehci-sched.c schedeling code does not like it when there are already urb's scheduled when (large) isoc urbs are queued. By moving the submission of the interrupt urbs to after submitting the isoc urbs the camera starts working again through usb-2.0 hubs. Note that this does not fix isoc. streaming through a usb-hub while another 1.1 usb device (like the microphone of the same cam) is also active at the same time :( I've spend a long time analyzing the linux kernel ehci scheduler code, resulting in this (long) mail: http://www.spinics.net/lists/linux-usb/msg37982.html The conclusion of the following mail thread is that yes there are several issues when using usb-1.1 devices through a usb-2.0 hub, but these are not easily fixable in the current code. Fixing this in ehci-sched.c requires an almost full rewrite, which is not bound to happen anytime soon. So with this patch gspca driven usb-1.1 webcams will atleast work when connected through an usb-2.0 hub when the microphone is not used. As an added bonus this patch avoids extra destroy/create input urb cycles when we end up falling back to a lower speed alt setting because of bandwidth limitations. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com> |
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