[Qemu-devel] [PATCH 0/3] usb-linux do not send unnecessary GET_CONFIGURATION

[Hans de Goede <hdegoede@redhat.com>]

Hi All,

First a short self-into. I've been a FOSS developer for 10+ years,
working on a large variety of projects. Most relevant for my appearing
here on the qemu list is my experience in reverse engineering and writing
usb webcam drivers for the Linux kernel and libgphoto2 camlibs for various
small usb keychain picture frames (with proprietary protocols).

I've been a Red Hat employee for 2 years now and in August this year I've
joined Red Hat's SPICE team. I'm currently tasked with looking into /
developing an usb redirection solution for SPICE. So for starters I've begun
looking into the current usb redirection support in qemu.

It failed at the first device I threw at it (a usb keychain picture frame),
the problem is that this (el cheapo) device does not seem to grok
GET_CONFIGURATION. This patch sets makes this device work (and stops qemu
from unnecessary sending a GET_CONFIGURATION ctrl msg in general) by
reading this value directly from sysfs.

Regards,

Hans

p.s.

While looking at the code I also noticed that the ep numeration in usb-linux
seems completely wrong for multifunction devices. I'll go test that and fix
it (assuming I'm right about it being wrong) tomorrow.