Well, I found something. After 13 kernel builds (not counting working around broken commits several times) and countless reboots, I found myself staring at this as the culprit:
commit e1620d591a75a10b15cf61dbf8243a0b7e6731a2 Author: Rafael J. Wysocki <[email protected]> Date: Fri Mar 18 19:55:36 2011 +0100 USB: Move runtime PM callbacks to usb_device_pm_ops USB defines usb_device_type pointing to usb_device_pm_ops that provides system-wide PM callbacks only and usb_bus_type pointing to usb_bus_pm_ops that provides runtime PM callbacks only. However, the USB runtime PM callbacks may be defined in usb_device_pm_ops which makes it possible to drop usb_bus_pm_ops and will allow us to consolidate the handling of subsystems by the PM core code. Signed-off-by: Rafael J. Wysocki <[email protected]> Acked-by: Greg Kroah-Hartman <[email protected]> I actually went back and started testing several of the earlier steps in the bisection because I couldn't believe this was the issue, since the commit looked completely irrelevant. Maybe I'd not tested thoroughly enough and falsely labeled as "good" one of the "bad" commits. But then I looked more closely at the patch associated with this commit, and decided to play around with some settings. With USB power management turned on in the current kernel (default in 3.2.0-25), all I have to do is run guvcview once after plugging in the webcam, close guvcview, wait at least two seconds (which is the default autosuspend idle-delay time), then open guvcview again. Voila! Bug reproduced. However, if I turn off USB power management), then this issue is no longer reproducible. I do this by running "echo -1 > /sys/module/usbcore/parameters/autosuspend" as root. I have not yet found a way to turn off autosuspend for just the webcam, but this appears to be a (somewhat sledgehammer-ish) workaround. So... now what? Have I found a kernel bug, or just a bug in the webcam firmware tickled by a legitimate change in the kernel code? If the latter, then is there a way to indicate that this particular webcam is not compatible with USB autosuspend as implemented now? -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1017072 Title: 046d:08c1 Regression: Quickcam Fusion doesn't work after first time To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1017072/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
