On 05/12/12 03:32, David Fries wrote: > I was bit in kvm-qemu (Debian qemu-kvm-1.0+dfsg-11) with the usb > descriptor parsing code. I was enhancing a driver in the guest and > found that I could talk to usb alt 0, but not alt 3, I made a local > fix and I see there is an upstream fix (listed below) in qemu. > > commit 96dd9aac37d30f3425088f81523942e67b2d03ac > Author: Gerd Hoffmann <kra...@redhat.com> > Date: Thu Mar 29 16:06:28 2012 +0200 > usb-host: rewrite usb_linux_update_endp_table
Yea, that one should fix it ;) > I'm curious why qemu/qemu-kvm even bothers? As far as I could tell > parsing the descriptor table is only used to deny the guest from > submitting urbs on the wrong pipe. No. It uses the wMaxPacketSize to pick a useful buffer size for iso endpoints. In master / upcoming 1.1 usb-host enables pipelining for bulk endpoints. Beside that enabling the usb_host_parse_* tracepoints gives a useful trace of guest activities (you should see your guest picking alt #3). cheers, Gerd
