usbhid: HP LD4200tm touchscreen ALMOST works

From: William Sherman
Date: Mon Oct 25 2010 - 20:09:24 EST

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Hello,

I'm looking to dig into the usbhid driver code to get me the last
mile and get my HP LD4200tm touchscreen working on my Linux system.
[NOTE: I posted about this elsewhere, but as I think about it more,
this is more of a linux-kernel issue than anything else, so I'm
reprising that note here.]

So, in first connecting the HP touchscreen (with touchscreen hardware
from Nexio) to the Linux system (running Ubuntu 10.10 -- 2.6.35-22 generic)
things were looking up, as the unit almost worked right out of the box
as a plug-and-play device. Unfortunately, that last mile needs to be
addressed in order for the unit to work in a useful way. I think I've
narrowed down the problem to the usbhid driver, as I'll explain in a
moment, and while I expect I have the ability to debug and fix the issue,
this would be my first dive into Linux driver coding, so I could probably
use a pointer as to what steps are necessary to get the proper kernel
sources, compile the needed parts and restart the system (hopefully
just restart X-windows) to test my edits (especially since Ubuntu tends
to not include a not of the necessary components).

I've collected gobs of data on what udev, hidraw, evtest and X-windows
report, but before I get to any of that, here's the executive summary:

Plugging the HP LD4200tm into a Ubuntu 10.10 system will cause the
device to be recognized, create a usbhid device, create an event device,
activate the evdev driver for Xorg, and put it on the list of X's inputs.
So far, so good.

Touching the device causes the mouse pointer to jump to that location,
even better.

But when I'm touching the screen, what happens is that the system
generates a continuous stream of button presses/releases -- as if
I moved the mouse to a particular location and then went crazy
tapping on the mouse button. This is the part that makes the system
unusable.

One more data point is that if I touch the screen with a second
finger, the button barrage stops, and it will now gracefully report
the movement of the first finger.

So all I need to do is modify the driver for this device's protocol
to not send all the unnecessary release/press events.

Here is the data that leads me to believe the issue is at the usbhid
layer:

1) Running "evtest /dev/input/event4" reveals that the button barrage
is already occurring at the HID event layer.

2) Watching the raw data on /dev/usb/hiddev2 does report a stream of
data as the touchscreen is touched (and no data when it's not touched),
looking at the output suggests that the device is only reporting touch/
release events when the screen is actually touched or released. And of
course, even if the device were reporting things poorly, I figure the
usbhid driver could be written to overcome this.

Fortunately, the data seems to be a constant 14-byte stride, so I
wrote a simple awk script ("nexio") to reformat the data as I was
figuring out the raw protocol. Here's a sample of the reformatted
data, followed by my estimation of the protocol:
% sudo xxd -c 14 -g 1 /dev/hidraw2 | nexio
0000000: 01 03 01 12d8 3357 02 02 15e1 1f71 01
000000e: 01 03 01 12cc 332a 02 02 15e1 1f71 01
000001c: 01 03 01 12de 3335 00 02 15e1 1f71 01
000002a: 01 03 01 12f4 3346 00 02 15e1 1f71 01
0000038: 01 03 01 1304 3352 00 02 15e1 1f71 01
0000046: 01 03 01 130c 3358 00 02 15e1 1f71 01
[... (next I stop touching the screen, and then touch it again)]
00009a0: 01 03 01 12d8 3357 00 02 15e1 1f71 01
00009ae: 01 03 01 12d8 3357 00 02 15e1 1f71 01
00009bc: 01 02 01 12d8 3357 00 02 15e1 1f71 01
00009ca: 01 03 01 10af 3681 02 02 15e1 1f71 01
00009d8: 01 03 01 10a5 3651 02 02 15e1 1f71 01
00009e6: 01 03 01 10b7 3654 00 02 15e1 1f71 01
[... (next is a multi-touch event)]
0000c78: 01 03 01 1019 3627 00 02 15e1 1f71 01
0000c86: 01 03 01 1019 3627 00 02 15e1 1f71 01
0000c94: 01 00 01 100b 35f8 00 02 1585 3110 00
0000ca2: 01 00 01 100e 3604 00 02 158a 311b 00
0000cb0: 01 00 01 1013 3615 00 02 1591 312b 00
0000cbe: 01 00 01 1017 3622 00 02 1596 3136 00
0000ccc: 01 00 01 1019 3628 00 02 1598 313c 00
0000cda: 01 00 01 1019 3629 00 02 1599 313d 00
0000ce8: 01 03 01 1019 3629 03 02 1598 313d 02
0000cf6: 01 03 01 1019 3628 03 02 1598 313c 02
0000d04: 01 03 01 1019 3627 03 02 1598 313b 02
0000d12: 01 03 01 1018 3627 03 02 1597 313a 02
[... (next I release both fingers -- not quite simultaneously)]
0000df2: 01 03 01 1019 3627 03 02 1598 3132 02
0000e00: 01 03 01 1019 3627 03 02 1598 3132 02
0000e0e: 01 03 01 1019 3627 02 02 1598 3132 01
0000e1c: 01 03 01 1019 3626 02 02 1598 3132 01
0000e2a: 01 03 01 1019 3626 00 02 1598 3132 01
0000e38: 01 03 01 1019 3626 00 02 1598 3132 01
0000e46: 01 03 01 1019 3626 00 02 1598 3132 01
0000e54: 01 03 01 1019 3626 00 02 1598 3132 01
0000e62: 01 03 01 1019 3625 00 02 1598 3132 01
0000e70: 01 02 01 1019 3625 00 02 1598 3132 01

Decoding the above:
- column 1: just a reprint of the xxd byte count
- column 2: always 01 -- probably a data packet sync byte
- column 3: usually 03 (which means an on-going touch event)
- 02 seems to indicate a touch-release event
- 00 seems to indicate a transition to a dual-touch event
- column 4: always 01 -- probably an indicator that the next two
words are the X/Y values for touch #1
- column 5: value of X location of touch #1
- column 6: value of Y location of touch #1
- column 7: usually 00
- 02 seems to mean initiation of a single-touch event
- 03 seems to indicate an on-going dual-touch event
- column 8: always 02 -- probably an indicator that the next two
words are the X/Y values for touch #2
- column 9: value of X location of touch #2
- column 10:value of Y location of touch #2
- column 11: usually 01 or 02 representing the number of contact points
- will be 00 when transitioning from single to dual
contact touch event

The rest of this email is a sample of some of the data that I've
collected about what the system reports. I think this should be
sufficient to get across all necessary information, but I have
more if warrented.

% xinput list --short 10
Nexio Touch Device. HID Multi-Touch id=10 [slave pointer (2)]
% xinput test 10
motion a[0]=15177 a[1]=5581 a[2]=15479 a[3]=7829 a[4]=0 a[5]=0
motion a[6]=0 a[7]=0 a[8]=0 a[9]=0 a[10]=0
button press 1
button release 1
button press 1
button release 1
button press 1
button release 1
button press 1
button release 1
button press 1
button release 1
button press 1
button release 1
[...]

So you can see that at first contact the location of the touch is reported,
but then there is the continual stream of button press/release.

Here is the output from "evtest" from a single finger interaction:
% sudo evtest /dev/input/event4
Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x1870 product 0x100 version 0x111
Input device name: "Nexio Touch Device. HID Multi-Touch"
Supported events:
Event type 0 (Sync)
Event type 1 (Key)
Event code 272 (LeftBtn)
Event code 273 (RightBtn)
Event code 274 (MiddleBtn)
Event code 320 (ToolPen)
Event code 321 (ToolRubber)
Event code 322 (ToolBrush)
Event code 330 (Touch)
Event type 3 (Absolute)
Event code 0 (X)
Value 15129
Min 0
Max 16383
Event code 1 (Y)
Value 6425
Min 0
Max 16383
Event code 2 (Z)
Value 14859
Min 0
Max 16383
Event code 3 (Rx)
Value 7160
Min 0
Max 16383
Event code 4 (Ry)
Value 0
Min 0
Max 32767
Event code 5 (Rz)
Value 0
Min 0
Max 32767
Event code 6 (Throttle)
Value 0
Min 0
Max 16383
Event code 7 (Rudder)
Value 0
Min 0
Max 16383
Event code 40 (Misc)
Value 1
Min 0
Max 1
Event code 41 (?)
Value 2
Min 0
Max 1
Event code 42 (?)
Value 1
Min 0
Max 2
Event type 4 (Misc)
Event code 4 (ScanCode)
Testing ... (interrupt to exit)
Event: time 1287784276.760109, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784276.760112, type 1 (Key), code 330 (Touch), value 1
Event: time 1287784276.760119, type 3 (Absolute), code 0 (X), value 14976
Event: time 1287784276.760122, type 3 (Absolute), code 1 (Y), value 7291
Event: time 1287784276.760125, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784276.760127, type 1 (Key), code 330 (Touch), value 0
Event: time 1287784276.760130, type 1 (Key), code 321 (ToolRubber), value 1
Event: time 1287784276.760139, -------------- Report Sync ------------
Event: time 1287784276.773107, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784276.773111, type 1 (Key), code 330 (Touch), value 1
Event: time 1287784276.773117, type 3 (Absolute), code 0 (X), value 14925
Event: time 1287784276.773120, type 3 (Absolute), code 1 (Y), value 7266
Event: time 1287784276.773123, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784276.773124, type 1 (Key), code 330 (Touch), value 0
Event: time 1287784276.773135, -------------- Report Sync ------------
Event: time 1287784276.785094, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784276.785099, type 1 (Key), code 330 (Touch), value 1
Event: time 1287784276.785105, type 3 (Absolute), code 0 (X), value 14937
Event: time 1287784276.785108, type 3 (Absolute), code 1 (Y), value 7269
Event: time 1287784276.785112, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784276.785113, type 1 (Key), code 330 (Touch), value 0
Event: time 1287784276.785116, type 1 (Key), code 321 (ToolRubber), value 0
Event: time 1287784276.785125, -------------- Report Sync ------------
^C

And here is the output of "evtest" from when I touched the screen with
two fingers:
% sudo evtest /dev/input/event4
Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x1870 product 0x100 version 0x111
Input device name: "Nexio Touch Device. HID Multi-Touch"
Supported events:
Event type 0 (Sync)
Event type 1 (Key)
Event code 272 (LeftBtn)
Event code 273 (RightBtn)
Event code 274 (MiddleBtn)
Event code 320 (ToolPen)
Event code 321 (ToolRubber)
Event code 322 (ToolBrush)
Event code 330 (Touch)
Event type 3 (Absolute)
Event code 0 (X)
Value 14937
Min 0
Max 16383
Event code 1 (Y)
Value 7269
Min 0
Max 16383
Event code 2 (Z)
Value 14859
Min 0
Max 16383
Event code 3 (Rx)
Value 7160
Min 0
Max 16383
Event code 4 (Ry)
Value 0
Min 0
Max 32767
Event code 5 (Rz)
Value 0
Min 0
Max 32767
Event code 6 (Throttle)
Value 0
Min 0
Max 16383
Event code 7 (Rudder)
Value 0
Min 0
Max 16383
Event code 40 (Misc)
Value 1
Min 0
Max 1
Event code 41 (?)
Value 2
Min 0
Max 1
Event code 42 (?)
Value 1
Min 0
Max 2
Event type 4 (Misc)
Event code 4 (ScanCode)
Testing ... (interrupt to exit)
Event: time 1287784360.966997, type 1 (Key), code 320 (ToolPen), value 0
Event: time 1287784360.967004, type 3 (Absolute), code 0 (X), value 14717
Event: time 1287784360.967006, type 3 (Absolute), code 1 (Y), value 6211
Event: time 1287784360.967014, type 3 (Absolute), code 2 (Z), value 15680
Event: time 1287784360.967016, type 3 (Absolute), code 3 (Rx), value 6211
Event: time 1287784360.967019, type 3 (Absolute), code 42 (?), value 0
Event: time 1287784360.967020, -------------- Report Sync ------------
Event: time 1287784360.979997, type 3 (Absolute), code 0 (X), value 14667
Event: time 1287784360.980001, type 3 (Absolute), code 1 (Y), value 6189
Event: time 1287784360.980008, type 3 (Absolute), code 2 (Z), value 15626
Event: time 1287784360.980011, type 3 (Absolute), code 3 (Rx), value 6189
Event: time 1287784360.980014, -------------- Report Sync ------------
Event: time 1287784360.992997, type 3 (Absolute), code 0 (X), value 14684
Event: time 1287784360.993000, type 3 (Absolute), code 1 (Y), value 6195
Event: time 1287784360.993008, type 3 (Absolute), code 2 (Z), value 15640
Event: time 1287784360.993011, type 3 (Absolute), code 3 (Rx), value 6195
Event: time 1287784360.993014, -------------- Report Sync ------------
Event: time 1287784361.005998, type 3 (Absolute), code 0 (X), value 14715
Event: time 1287784361.006001, type 3 (Absolute), code 1 (Y), value 6220
Event: time 1287784361.006008, type 3 (Absolute), code 2 (Z), value 15660
Event: time 1287784361.006011, type 3 (Absolute), code 3 (Rx), value 6220
Event: time 1287784361.006014, -------------- Report Sync ------------
Event: time 1287784361.018000, type 3 (Absolute), code 0 (X), value 14745
Event: time 1287784361.018004, type 3 (Absolute), code 1 (Y), value 6278
Event: time 1287784361.018012, type 3 (Absolute), code 2 (Z), value 15674
Event: time 1287784361.018014, type 3 (Absolute), code 3 (Rx), value 6278
Event: time 1287784361.018017, -------------- Report Sync ------------
Event: time 1287784361.030997, type 3 (Absolute), code 0 (X), value 14767
Event: time 1287784361.031000, type 3 (Absolute), code 1 (Y), value 6358
Event: time 1287784361.031008, type 3 (Absolute), code 2 (Z), value 15680
Event: time 1287784361.031010, type 3 (Absolute), code 3 (Rx), value 6358
Event: time 1287784361.031013, -------------- Report Sync ------------
Event: time 1287784361.043996, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784361.043999, type 1 (Key), code 330 (Touch), value 1
Event: time 1287784361.044001, type 1 (Key), code 320 (ToolPen), value 1
Event: time 1287784361.044006, type 3 (Absolute), code 0 (X), value 14777
Event: time 1287784361.044008, type 3 (Absolute), code 1 (Y), value 6451
Event: time 1287784361.044012, type 1 (Key), code 321 (ToolRubber), value 1
Event: time 1287784361.044016, type 3 (Absolute), code 2 (Z), value 15682
Event: time 1287784361.044019, type 3 (Absolute), code 3 (Rx), value 6451
Event: time 1287784361.044021, type 3 (Absolute), code 42 (?), value 2
Event: time 1287784361.044023, -------------- Report Sync ------------
Event: time 1287784361.057000, type 3 (Absolute), code 0 (X), value 14779
Event: time 1287784361.057004, type 3 (Absolute), code 1 (Y), value 6546
Event: time 1287784361.057012, type 3 (Absolute), code 3 (Rx), value 6546
Event: time 1287784361.057016, -------------- Report Sync ------------
Event: time 1287784361.069998, type 3 (Absolute), code 0 (X), value 14778
Event: time 1287784361.070001, type 3 (Absolute), code 1 (Y), value 6640
Event: time 1287784361.070009, type 3 (Absolute), code 2 (Z), value 15681
Event: time 1287784361.070011, type 3 (Absolute), code 3 (Rx), value 6640
Event: time 1287784361.070014, -------------- Report Sync ------------
Event: time 1287784361.081989, type 3 (Absolute), code 0 (X), value 14776
Event: time 1287784361.081992, type 3 (Absolute), code 1 (Y), value 6733
Event: time 1287784361.082000, type 3 (Absolute), code 2 (Z), value 15680
Event: time 1287784361.082002, type 3 (Absolute), code 3 (Rx), value 6733
Event: time 1287784361.082005, -------------- Report Sync ------------
Event: time 1287784361.094987, type 3 (Absolute), code 0 (X), value 14775
Event: time 1287784361.094990, type 3 (Absolute), code 1 (Y), value 6832
Event: time 1287784361.094998, type 3 (Absolute), code 2 (Z), value 15679
Event: time 1287784361.095000, type 3 (Absolute), code 3 (Rx), value 6832
Event: time 1287784361.095004, -------------- Report Sync ------------
Event: time 1287784361.107986, type 3 (Absolute), code 0 (X), value 14774
Event: time 1287784361.107990, type 3 (Absolute), code 1 (Y), value 6939
Event: time 1287784361.107999, type 3 (Absolute), code 3 (Rx), value 6939
Event: time 1287784361.108002, -------------- Report Sync ------------
Event: time 1287784361.121001, type 3 (Absolute), code 1 (Y), value 7042
Event: time 1287784361.121011, type 3 (Absolute), code 3 (Rx), value 7042
Event: time 1287784361.121014, -------------- Report Sync ------------
Event: time 1287784361.132987, type 3 (Absolute), code 0 (X), value 14779
Event: time 1287784361.132991, type 3 (Absolute), code 1 (Y), value 7138
Event: time 1287784361.132999, type 3 (Absolute), code 3 (Rx), value 7138
Event: time 1287784361.133003, -------------- Report Sync ------------
Event: time 1287784361.145998, type 3 (Absolute), code 0 (X), value 14794
Event: time 1287784361.146001, type 3 (Absolute), code 1 (Y), value 7221
Event: time 1287784361.146010, type 3 (Absolute), code 3 (Rx), value 7221
Event: time 1287784361.146014, -------------- Report Sync ------------
Event: time 1287784361.158999, type 3 (Absolute), code 0 (X), value 14815
Event: time 1287784361.159003, type 3 (Absolute), code 1 (Y), value 7284
Event: time 1287784361.159010, type 3 (Absolute), code 2 (Z), value 15684
Event: time 1287784361.159012, type 3 (Absolute), code 3 (Rx), value 7284
Event: time 1287784361.159016, -------------- Report Sync ------------
Event: time 1287784361.183994, type 4 (Misc), code 4 (ScanCode), value d0042
Event: time 1287784361.183996, type 1 (Key), code 330 (Touch), value 0
Event: time 1287784361.184014, -------------- Report Sync ------------
^C

So you can see that the location of both fingers is reported for the
multi-touch operation (with one finger reported as X & Y, and the
second finger as Z & Rx). But with one finger, it's a bunch of button
presses and then nearly instantaneous releases.

And one final bit of information. Here is the relevant information from
the udev.log:
-----------------------------
UDEV [1287664208.316717] add /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2:1.0/input/input4/event4 (input)
UDEV_LOG=3
ACTION=add

DEVPATH=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2:1.0/input/input4/event4
SUBSYSTEM=input
DEVNAME=/dev/input/event4
SEQNUM=1272
ID_INPUT=1
ID_INPUT_TABLET=1
ID_VENDOR=Nexio_Touch_Device.
ID_VENDOR_ENC=Nexio\x20Touch\x20Device.\x20\x20
ID_VENDOR_ID=1870
ID_MODEL=HID_Multi-Touch
ID_MODEL_ENC=HID\x20Multi-Touch
ID_MODEL_ID=0100
ID_REVISION=0006
ID_SERIAL=Nexio_Touch_Device._HID_Multi-Touch
ID_TYPE=hid
ID_BUS=usb
ID_USB_INTERFACES=:030000:
ID_USB_INTERFACE_NUM=00
ID_USB_DRIVER=usbhid
ID_PATH=pci-0000:00:1d.2-usb-0:2:1.0
MAJOR=13
MINOR=68
DEVLINKS=/dev/char/13:68 /dev/input/by-id/usb-Nexio_Touch_Device._HID_Multi-Touch-event-mouse /dev/input/by-path/pci-0000:00:1d.2-usb-0:2:1.0-event-mouse

UDEV [1287664208.316759] add /devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2:1.0/input/input4/mouse1 (input)
UDEV_LOG=3
ACTION=add

DEVPATH=/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2:1.0/input/input4/mouse1
SUBSYSTEM=input
DEVNAME=/dev/input/mouse1
SEQNUM=1273
ID_INPUT=1
ID_INPUT_TABLET=1
ID_VENDOR=Nexio_Touch_Device.
ID_VENDOR_ENC=Nexio\x20Touch\x20Device.\x20\x20
ID_VENDOR_ID=1870
ID_MODEL=HID_Multi-Touch
ID_MODEL_ENC=HID\x20Multi-Touch
ID_MODEL_ID=0100
ID_REVISION=0006
ID_SERIAL=Nexio_Touch_Device._HID_Multi-Touch
ID_TYPE=hid
ID_BUS=usb
ID_USB_INTERFACES=:030000:
ID_USB_INTERFACE_NUM=00
ID_USB_DRIVER=usbhid
ID_PATH=pci-0000:00:1d.2-usb-0:2:1.0
MAJOR=13
MINOR=33
DEVLINKS=/dev/char/13:33 /dev/input/by-id/usb-Nexio_Touch_Device._HID_Multi-Touch-mouse /dev/input/by-path/pci-0000:00:1d.2-usb-0:2:1.0-mouse
-----------------------------

And if that isn't enough info, I'm happy to provide more.

Thanks for whatever suggestions you can provide,
Bill

--
Bill Sherman
Sr. Technology Advisor
Advanced Visualization Lab
Pervasive Technology Inst
Indiana University
shermanw@xxxxxxxxxxx
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