Comment 59 for bug 1326725

...or much more likely that the bug was never there in the first place... :(

Looking into /usr/src/linux-headers-3.13.11-03131105/include/linux/hid.h shows that the changes that caused the regression that I pointed out in comment #55 might not have been applied to this kernel at all.

To be more precise I'm talking about some of the changes in this commit:
commit aa6c390c4d59c9ff4fffd887e15783b2b793951b
Author: Benjamin Tissoires

    HID: remove hid_get_raw_report in struct hid_device

I can see that "hid_get_raw_report" is still there in /usr/src/linux-headers-3.13.11-03131105/include/linux/hid.h
while, for instance, in /usr/src/linux-headers-3.13.0-32/include/linux/hid.h it's not there anymore.

That leads me to believe that the fix from 3.14 is not there because the bug itself is not there either.

The bug was caused by backporting some synaptics hid driver from upstream to the trusty kernel.
That's why the ubuntu trusty kernel is affected while 3.13 mainline is not.