tree 63df7a8374a21f8298a72d6d5a7832c74398c3e0
parent b4fbe1f65a4769c09e6bf2d79fc84360f840f40e
author Gerd Hoffmann <kraxel@redhat.com> 1547124668 +0100
committer Gerd Hoffmann <kraxel@redhat.com> 1548827272 +0100

usb: assign unique serial numbers to hid devices

Windows guests have trouble dealing with usb devices having identical
serial numbers.  So, assign unique serial numbers to usb hid devices.
All other usb devices have this already.

In the past the fixed serial number has been used to indicate working
remote setup to linux guests.  Here is a bit of history:

 * First there was nothing.
 * Then I added a rule to udev checking for serial == 42.
   (this is in rhel-6).
 * Then systemd + udev merged.
 * Then I changed the rule to check for serial != 1 instead, so we can
   use any serial but "1" which is the one the old broken devices had
   (this is in rhel-7).  March 2014 in upstream systemd.
 * Then all usb power management rules where dropped from systemd (June
   2015).  Which I figured today (Sept 2018), after wondering that the
   rules are gone in fedora 28.

So, three years ago the serial number check was dropped upstream, yet I
hav't seen a single report about autosuspend issues (or cpu usage for
usb emulation going up, which is the typical symtom).

So I figured I can stop worring that changing the serial number will
break things and just do it.

And even if it turns out autosuspend is still an issue:  I think
meanwhile we can really stop worrying about guests running in old qemu
versions with broken usb suspend (fixed in 0.13 !).  If needed we can
enable autosuspend unconditionally in guests.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20190110125108.22834-1-kraxel@redhat.com