[Qemu-discuss] QEMU, USB passthrough and libusb_set_configuration

[Manfred Haertel, DB3HM]

QEMU's USB passthrough was not working for my new smartphone.

While analyzing the problem, I found out that a SET CONFIGURATION 
Request was NACKed by the USB device.

I do not understand why. is it possible, that is was NACKed, because it 
was the second SET CONFIGURATION request (because it seems that the host 
already sent a SET CONFIGURATION request before QEMU tried to claim the 
device)?

Anyway, I wrote a simple program to "fake" a successful call to 
libusb_set_configuration and did an LD_PRELOAD on this program before 
starting qemu, and it worked.

Looking at QEMU's code in host-libusb.c, I can see that QEMU does not 
try to claim the interface if its call to libusb_set_configuration 
failes, so that's probably the problem.

Though the actual problem may be in the USB device, shouldn't QEMU be 
more conservative if libusb_set_configuration fails and try to claim the 
device anyway?

--
Manfred Härtel, DB3HM    mailto:address@hidden
                         http://rz-home.de/mhaertel