Ubuntu – How to correct this mismapped stylus button

keycodesremappingstylustouchscreenudev

I'm running Kubuntu 15.10 on an HP Spectre x360, which has a non-Wacom active digitizer built into the display. I'm using a two-button stylus with this, but the second button doesn't work. I couldn't get xinput to show any state change when the button is pressed; it seems X can't see it at all. evtest does see an event, but it reports the button as BTN_TOOL_RUBBER instead of the appropriate BTN_STYLUS2:

Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x4f3 product 0x2073 version 0x110
Input device name: "ELAN Touchscreen Pen"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 256 (BTN_0)
    Event code 320 (BTN_TOOL_PEN)
    Event code 321 (BTN_TOOL_RUBBER)
    Event code 330 (BTN_TOUCH)
    Event code 331 (BTN_STYLUS)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value  23080
      Min        0
      Max    32256
      Resolution     110
    Event code 1 (ABS_Y)
      Value  10408
      Min        0
      Max    17920
      Resolution     108
    Event code 24 (ABS_PRESSURE)
      Value      0
      Min        0
      Max      255
  Event type 4 (EV_MSC)
    Event code 4 (MSC_SCAN)
Properties:
Testing ... (interrupt to exit)
Event: time 1453608432.242049, type 1 (EV_KEY), code 321 (BTN_TOOL_RUBBER), value 1
Event: time 1453608432.242049, -------------- SYN_REPORT ------------

The stylus has no eraser tip. input-kbd gives me the scancodes and shows the same issue:

/dev/input/event8
   bustype : BUS_USB
   vendor  : 0x4f3
   product : 0x2073
   version : 272
   name    : "ELAN Touchscreen Pen"
   phys    : "usb-0000:00:14.0-4/input0"
   uniq    : ""
   bits ev : EV_SYN EV_KEY EV_ABS EV_MSC

map: 15 keys, size: 294/320
0xd0032 = 320  # BTN_TOOL_PEN
0xd0042 = 330  # BTN_TOUCH
0xd0044 = 331  # BTN_STYLUS
0xd003c = 321  # BTN_TOOL_RUBBER
0xd0045 = 256  # BTN_0
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH
0xd0042 = 330  # BTN_TOUCH

Trying to use input-kbd to assign a new map gives a "scancode out of range" error. The straightforward setkeycodes d003c 332 also does not work (USB keyboard bug).

Update: I've tried fixing this through udev by adding a custom hwdb file to /etc/udev/hwdb.d, but it doesn't seem to be having any effect.

$ cat /etc/udev/hwdb.d/61-touchscreen-quirks.hwdb 
evdev:input:b0003v04f3p2073e0110*   # Matches ELAN Touchscreen devices
 KEYBOARD_KEY_d003c=14c             # Reassigns scancode from BTN_TOOL_RUBBER to BTN_STYLUS2

$ sudo udevadm --debug hwdb --update
calling: hwdb
reading file '/lib/udev/hwdb.d/20-OUI.hwdb'
reading file '/lib/udev/hwdb.d/20-acpi-vendor.hwdb'
reading file '/lib/udev/hwdb.d/20-bluetooth-vendor-product.hwdb'
reading file '/lib/udev/hwdb.d/20-libgphoto2-6.hwdb'
reading file '/lib/udev/hwdb.d/20-net-ifname.hwdb'
reading file '/lib/udev/hwdb.d/20-pci-classes.hwdb'
reading file '/lib/udev/hwdb.d/20-pci-vendor-model.hwdb'
reading file '/lib/udev/hwdb.d/20-sdio-classes.hwdb'
reading file '/lib/udev/hwdb.d/20-sdio-vendor-model.hwdb'
reading file '/lib/udev/hwdb.d/20-usb-classes.hwdb'
reading file '/lib/udev/hwdb.d/20-usb-media-players.hwdb'
reading file '/lib/udev/hwdb.d/20-usb-vendor-model.hwdb'
reading file '/lib/udev/hwdb.d/60-evdev.hwdb'
reading file '/lib/udev/hwdb.d/60-keyboard.hwdb'
reading file '/etc/udev/hwdb.d/61-touchscreen-quirks.hwdb'
reading file '/lib/udev/hwdb.d/69-libmtp.hwdb'
reading file '/lib/udev/hwdb.d/70-mouse.hwdb'
reading file '/lib/udev/hwdb.d/70-pointingstick.hwdb'
=== trie in-memory ===
nodes:             3899920 bytes (   97498)
children arrays:   1559952 bytes (   97497)
values arrays:     1241904 bytes (   77619)
strings:           1721567 bytes
strings incoming:  4005992 bytes (  240722)
strings dedup'ed:  2347672 bytes (  177476)
=== trie on-disk ===
size:              6863455 bytes
header:                 80 bytes
nodes:             2339952 bytes (   97498)
child pointers:    1559952 bytes (   97497)
value pointers:    1241904 bytes (   77619)
string store:      1721567 bytes
strings start:     5141888

$ sudo udevadm -d control --reload
calling: control

$ sudo udevadm -d trigger /dev/input/event*
calling: trigger

$ sudo udevadm info -q all -p /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.0/0003:04F3:2073.0004/input/input9
P: /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.0/0003:04F3:2073.0004/input/input9
E: ABS=1000003
E: DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.0/0003:04F3:2073.0004/input/input9
E: EV=1b
E: ID_BUS=usb
E: ID_FOR_SEAT=input-pci-0000_00_14_0-usb-0_4_1_0
E: ID_INPUT=1
E: ID_INPUT_TABLET=1
E: ID_MODEL=Touchscreen
E: ID_MODEL_ENC=Touchscreen
E: ID_MODEL_ID=2073
E: ID_PATH=pci-0000:00:14.0-usb-0:4:1.0
E: ID_PATH_TAG=pci-0000_00_14_0-usb-0_4_1_0
E: ID_REVISION=5107
E: ID_SERIAL=ELAN_Touchscreen
E: ID_TYPE=hid
E: ID_USB_DRIVER=usbhid
E: ID_USB_INTERFACES=:030000:
E: ID_USB_INTERFACE_NUM=00
E: ID_VENDOR=ELAN
E: ID_VENDOR_ENC=ELAN
E: ID_VENDOR_ID=04f3
E: KEY=c03 1 0 0 0 0
E: MODALIAS=input:b0003v04F3p2073e0110-e0,1,3,4,k100,140,141,14A,14B,ra0,1,18,m4,lsfw
E: MSC=10
E: NAME="ELAN Touchscreen Pen"
E: PHYS="usb-0000:00:14.0-4/input0"
E: PRODUCT=3/4f3/2073/110
E: PROP=0
E: SUBSYSTEM=input
E: TAGS=:seat:
E: UNIQ=""
E: USEC_INITIALIZED=4595650

What did I do wrong here, or alternatively, what is a better way of doing this?

Best Answer

I was finally able to remap the scancode to BTN_STYLUS2 using ir-keytable. The command was:

sudo ir-keytable --device /dev/input/event8 --set-key 0xd003c=BTN_STYLUS2

HOWEVER, while I could see that the scancode had been successfully rebound, the button remained dead. evtest no longer reported any event when the button was pressed.

Before this, there was no MSC_SCAN event reported by evtest when that button was pressed, though there were scancodes reported for the other button and also the pen touch. This didn't strike me as more than an odd quirk at the time, but now it seems like the button really does generate no scancode. How did evtest report a keycode event at all, then? Beats me, and at this point I'm chalking it up to a kernel bug.

In the end, I just kludged together a bash script to watch evtest for BTN_TOOL_RUBBER events and simulate a right-click with xdotool:

#!/bin/bash

# Find the input device number.
devicename="ELAN Touchscreen Pen"
numevents=$(ls /dev/input | grep -c event*)
for ((devnr=0;devnr<$numevents;devnr++)); do
    input-kbd $devnr | grep -q "$devicename"
    if [[ $? == 0 ]]; then
        break
    fi
done

# Listen for BTN_TOOL_RUBBER events.
evtest /dev/input/event$devnr | while read line; do
for value in {0..1}; do
    echo $line | grep -q "type 1 (EV_KEY), code 321 (BTN_TOOL_RUBBER), value $value"
    if [[ $? == 0 ]]; then
        case $value in
            0)  xdotool mouseup 3   ;;
            1)  xdotool mousedown 3 ;;
        esac
    fi
done
done

This gives me essentially the basic functionality I wanted anyways. It's not perfect: the mouseup event only happens once the pen leaves proximity, not when the button is released (this is when the BTN_TOOL_RUBBER key-up event is reported in evtest), but it works well enough that I'm not going to try debugging the kernel.

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