I've taken a long hard look at this bug and believe I've been able to
nail down the cause. The panic is caused by a NULL pointer being passed
to the 'input_report_switch' function. It occurs if the kernel has
probed the tablet's pen/pad interface and processes a status report from
it before the kernel has a chance to probe the tablet's touchpad
interface. The suggested workaround of loading the module before
connecting the tablet only masks the issue by changing the timing of
events enough so that the kernel is able to finish probing both
interfaces before processing the status report.
This issue was addressed upstream by commit 44b9683 ("HID: wacom - make
sure touch_input is valid before using it") which is part of the 3.19
kernel. Both the Trusty (3.13) and Vivid (3.16) kernels are missing this
patch, however. Commit 44b9683 can be trivially backported; I've
attached such a backport for convenience.
** Patch added: "Upstream 44b9683 modified to apply against Ubuntu's 3.13 and
3.16 kernels"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1310800/+attachment/4452940/+files/make-sure-touch_input-is-valid-before-using.patch
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1310800
Title:
056a:0302 Trusty Tahr, kernel 3.13: automatic load of wacom.ko driver
cause a "hard" kernel panic
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1310800/+subscriptions
--
ubuntu-bugs mailing list
ubuntu-bugs@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
