Hi Alan and Jürgen, On Friday 30 August 2013 11:02:15 Alan Stern wrote: > On Fri, 30 Aug 2013, Jürgen Liebmann wrote: > > Another mystery effect: > > > > I have Ubuntu with the same kernel installed in a virtual machine > > (virtualbox). > > > > When I plug in the camera in the host the error appears. > > > > Then I plug in the camera in the virtual machine camera works fine. > > And now I shut down virtual machine. > > > > Now I can use the camera in host until I remove the camera. > > A new plug in produces the error again. > > This does seem to indicate that the problem is in the camera. > > > Can it be that the time between the both Get-String-Descriptor requests > > are too small? > > You mean the time between the two class-specific requests? Yes, this > is possible. (But the commit you found increases that time, so it > should not have caused the problem to occur.) > > Anyway, if you want to increase the time between those two requests, > you will have to change the video driver. Maybe Laurent can help (see > the analysis below). Jürgen, could you please try to set the UVC_QUIRK_PROBE_DEF quirk (you can set the uvcvideo quirks parameter to 0x100 before plugging your webcam in) and see if it helps ? > > Am 28.08.2013 22:51, schrieb Alan Stern: > > > On Wed, 28 Aug 2013, Jürgen Liebmann wrote: > > >> In the attachment the both usbmon traces: > > >> > > >> usbmon-reverted.out (camera works ok) > > >> usbmon-74a6af256648 (camera fails) > > > > > > This is very strange indeed. Here's where the two traces start to get > > > different results. In the kernel with the commit reverted: > > > > > > ffff88023073f9c0 742830275 S Co:2:009:0 s 01 0b 0000 0001 0000 0 > > > ffff88023073f9c0 742830331 C Co:2:009:0 0 0 > > > ffff88023073f9c0 742830336 S Ci:2:009:0 s a1 87 0100 0001 001a 26 < > > > ffff88023073f9c0 742830583 C Ci:2:009:0 -32 0 > > > ffff88023073f9c0 742830592 S Ci:2:009:0 s a1 81 0100 0001 001a 26 < > > > ffff88023073f9c0 742831081 C Ci:2:009:0 0 26 = 01000101 15160500 > > > 00000000 00000000 00000018 0300fc03 0000 ffff88023073fc00 742831291 S > > > Ci:2:009:0 s 80 06 0302 0409 00ff 255 < ffff88023073fc00 742831583 C > > > Ci:2:009:0 0 52 = 34034d00 69006300 72006f00 73006f00 66007400 20004c00 > > > 69006600 65004300 > > > > > > This shows a successful Set-Interface request, followed by an > > > unsuccessful class-specific request and a successful class-specific > > > request which returns 26 data bytes. Following that, the computer > > > reads a 52-byte string descriptor. > > > > > > Now here's the same thing with the commit present: > > > > > > ffff880233820f00 1078447196 S Co:2:008:0 s 01 0b 0000 0001 0000 0 > > > ffff880233820f00 1078447253 C Co:2:008:0 0 0 > > > ffff880233739cc0 1078447266 S Ci:2:008:0 s a1 87 0100 0001 001a 26 < > > > ffff880233739cc0 1078447523 C Ci:2:008:0 -32 0 > > > ffff880233739cc0 1078447539 S Ci:2:008:0 s a1 81 0100 0001 001a 26 < > > > ffff880233739cc0 1078447898 C Ci:2:008:0 -32 0 > > > ffff880233739a80 1078448123 S Ci:2:008:0 s 80 06 0302 0409 00ff 255 < > > > ffff880233739a80 1078448542 C Ci:2:008:0 0 26 = 01000101 15160500 > > > 00000000 00000000 00000018 0300fc03 0000 ffff880233739a80 1078448556 S > > > Ci:2:008:0 s 80 06 0302 0409 00ff 255 < ffff880233739a80 1078448907 C > > > Ci:2:008:0 0 52 = 34034d00 69006300 72006f00 73006f00 66007400 20004c00 > > > 69006600 65004300 > > > > > > This starts with the same Set-Interface request and the same > > > unsuccessful class-specific request. But the second class-specific > > > request also fails, and the Get-String-Descriptor returns the 26 bytes > > > of class-specific data! The Get-String-Descriptor request is repeated, > > > and this time the device sends the correct 52-byte string descriptor. > > > After that everything seems to return to normal. > > > > > > I don't understand this at all. There is no way that commit could > > > cause the driver to malfunction like this. The only thing I can think > > > of is some sort of hardware problem, either in the computer or (less > > > likely) in the camera. > > > > > > Can you try testing this on a different computer? > > > > > > Alan Stern -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
