[Bug 1057824] Re: USB input device interfaces compete for the same symlink name in 60-persistent-input.rules

[Adam Conrad]

Hello a7x, or anyone else affected,

Accepted udev into precise-proposed. The package will build now and be
available at http://launchpad.net/ubuntu/+source/udev/175-0ubuntu9.2 in
a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to
enable and use -proposed.  Your feedback will aid us getting this update
out to other Ubuntu users.

If this package fixes the bug for you, please change the bug tag from
verification-needed to verification-done.  If it does not, change the
tag to verification-failed.  In either case, details of your testing
will help us make a better decision.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance!

** Tags added: verification-needed

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https://bugs.launchpad.net/bugs/1057824

Title:
  USB input device interfaces compete for the same symlink name in 60
  -persistent-input.rules

Status in “udev” package in Ubuntu:
  Fix Committed
Status in “udev” source package in Precise:
  Fix Committed
Status in “udev” source package in Quantal:
  Fix Committed

Bug description:
  The current rules in 60-persistent-input.rules do not produce a usable
  symlink for the interface 0 device in multi-interface USB input
  devices.

  These are the problematic rules:

  KERNEL=="mouse*|js*", ENV{ID_BUS}=="?*", ENV{.INPUT_CLASS}=="?*", SYMLINK+="input/by-id/$env{ID_BUS}-$env{ID_SERIAL}-$env{.INPUT_CLASS}"
  KERNEL=="event*", ENV{ID_BUS}=="?*", ENV{.INPUT_CLASS}=="?*", SYMLINK+="input/by-id/$env{ID_BUS}-$env{ID_SERIAL}-event-$env{.INPUT_CLASS}"

  The above rules can be matched by multiple devices if a USB input
  device has multiple USB interfaces (such as the Microsoft Wired
  Keyboard 600, which has two keyboard interfaces).  Because the
  generated symlink names do not include the USB interface number, the
  multiple devices will compete over the same symlink name.  According
  to the udev man page, the device that wins is undefined unless the
  devices are assigned different link_priority values (which they are
  not).

  There are other rules in 60-persistent-input.rules that do produce
  per-interface symlinks.  These rules were introduced in git commit
  5e9eb15 [1] for bug #626449.  Unfortunately, due to git commit 32567f8
  [2], a symlink for interface 0 is not produced by these per-interface
  rules.  Thus, if an interface other than 0 wins the competition for
  the colliding symlink names, there won't be a persistent symlink for
  the interface 0 device.  Even if device 0 does win the competition, it
  may change, going against the intended persistence.

  It seems like the correct fix is to give interface 0 a higher
  link_priority value than the other interfaces.  This would guarantee
  that interface 0 always wins the competition.

  [1] http://cgit.freedesktop.org/systemd/systemd/commit/?id=5e9eb156c003dc7f8f92287bfad0251d6c5d0ef9
  [2] http://cgit.freedesktop.org/systemd/systemd/commit/?id=32567f8c95290a8819c0bc7d57849b8abfba9554

  $ lsb_release -rd
  Description:    Ubuntu 12.04.1 LTS
  Release:        12.04
  $ apt-cache policy udev
  udev:
    Installed: 175-0ubuntu9.1
    Candidate: 175-0ubuntu9.1
    Version table:
   *** 175-0ubuntu9.1 0
          500 http://us.archive.ubuntu.com/ubuntu/ precise-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       175-0ubuntu9 0
          500 http://us.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages

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