Problems with a Zytronic touchscreen on kernel 3.5 (USB ID 0x14c8:0x0005) - regression from kernel 3.0

Hello,

Greg K-H pointed me this way from linux-usb; I've had no replies there, but if 
you've already seen the message on linux-usb, nothing's changed in the text 
below or the attachments.

I'm trying to get a Zytronic single-touch touchscreen to work with Linux 
kernel 3.5; it previously worked on a 3.0 kernel. I'm happy to try git kernels 
and patches, even if they're just intended to gather more information.

hid-multitouch is picking up the device because it has multitouch report 
descriptors as well as the single-touch descriptors. There's a quirk to make 
it use MT_CLS_SERIAL, but that seems to be insufficient for my needs.

I've got as far as determining that it's mt_event in hid-multitouch.c that 
consumes the events, but as the screen never sends the events hid-multitouch.c 
expects to see, mt_event nevers sends an input event.

evtest on 3.0 shows touch events as expected. evtest on 3.5 shows no touch 
events.

I've attached /sys/kernel/debug/hid/0003:14C8:0005.0001/rdesc as 
zyntronic.rdesc and /sys/kernel/debug/hid/0003:14C8:0005.0001/events while I 
touch the screen as zytronic.events.

I had evtest /dev/input/event5 running while I captured zytronic.events, and 
got the following output:

Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x14c8 product 0x5 version 0x101
Input device name: "Zytronic Displays Limited Zytronic Touchscreen Controller"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value      0
      Min        0
      Max     4096
    Event code 1 (ABS_Y)
      Value      0
      Min        0
      Max     4096
    Event code 47 (ABS_MT_SLOT)
      Value      0
      Min        0
      Max        9
    Event code 53 (ABS_MT_POSITION_X)
      Value      0
      Min        0
      Max     4096
    Event code 54 (ABS_MT_POSITION_Y)
      Value      0
      Min        0
      Max     4096
    Event code 57 (ABS_MT_TRACKING_ID)
      Value      0
      Min        0
      Max    65535
Testing ... (interrupt to exit)
^C

Any ideas, or instructions for gathering more debug information will be 
gratefully received.
-- 
Simon Farnsworth
Software Engineer
ONELAN Ltd
http://www.onelan.com