udev, the “authorized” attribute and other failed attempts to ban a bogus USB keyboard

Introduction

This is a spin-off post about failing attempts to fix the problem with a webcam’s keyboard buttons. Namely, that the a shaky physical connections caused the USB device to go on and off the bus rapidly, and consequently crash X windows. The background story is in this post.

There is really nothing to learn from this post regarding how to accomplish something. The only reason I don’t trash this is that there’s some possibly useful information about udev.

What I tried to do

There is a possibility to ban a USB device from being accessed by Linux, by virtue of the “authorized” attribute. Something like this.

# cd /sys/devices/pci0000:00/0000:00:14.0/usb2/2-5/
# echo 0 > authorized
^C^Z
# echo 1 > authorized
bash: echo: write error: Invalid argument

The ^C^Z after the first command is not a mistake. The first command got stuck for several seconds.

And this can be done with udev rules as well.

But surprisingly enough, there doesn’t seem to be a way to avoid the generation of the /dev/input/event* file without ignoring the USB device completely. It’s possible to delete it early enough, but that doesn’t really help, it turns out.

ATTRS{authorized} can be set to 0 only for the entire USB device. There is no such parameter for a udev event with the “input” subsystem.

Some udev queries

While trying to figure out the ATTRS{authorized} thing, these are my little play-arounds. Nothing really useful here:

$ sudo udevadm monitor --udev --property

I got

UDEV  [5662716.427855] add      /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1 (usb)
ACTION=add
BUSNUM=001
DEVNAME=/dev/bus/usb/001/098
DEVNUM=098
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1
DEVTYPE=usb_device
DRIVER=usb
ID_BUS=usb
ID_MODEL=USB2.0_PC_CAMERA
ID_MODEL_ENC=USB2.0\x20PC\x20CAMERA
ID_MODEL_ID=2311
ID_REVISION=0100
ID_SERIAL=Generic_USB2.0_PC_CAMERA
ID_USB_INTERFACES=:0e0100:0e0200:
ID_VENDOR=Generic
ID_VENDOR_ENC=Generic
ID_VENDOR_FROM_DATABASE=GEMBIRD
ID_VENDOR_ID=1908
MAJOR=189
MINOR=97
PRODUCT=1908/2311/100
SEQNUM=24413
SUBSYSTEM=usb
TYPE=239/2/1
USEC_INITIALIZED=5662716427506

UDEV  [5662716.430744] add      /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.1 (usb)
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.1
DEVTYPE=usb_interface
DRIVER=uvcvideo
ID_USB_CLASS_FROM_DATABASE=Miscellaneous Device
ID_USB_PROTOCOL_FROM_DATABASE=Interface Association
ID_VENDOR_FROM_DATABASE=GEMBIRD
INTERFACE=14/2/0
MODALIAS=usb:v1908p2311d0100dcEFdsc02dp01ic0Eisc02ip00in01
PRODUCT=1908/2311/100
SEQNUM=24420
SUBSYSTEM=usb
TYPE=239/2/1
USEC_INITIALIZED=5662716430425

UDEV  [5662716.430935] add      /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0 (usb)
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0
DEVTYPE=usb_interface
DRIVER=uvcvideo
ID_USB_CLASS_FROM_DATABASE=Miscellaneous Device
ID_USB_PROTOCOL_FROM_DATABASE=Interface Association
ID_VENDOR_FROM_DATABASE=GEMBIRD
INTERFACE=14/1/0
MODALIAS=usb:v1908p2311d0100dcEFdsc02dp01ic0Eisc01ip00in00
PRODUCT=1908/2311/100
SEQNUM=24414
SUBSYSTEM=usb
TYPE=239/2/1
USEC_INITIALIZED=5662716430396

UDEV  [5662716.433265] add      /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/media5 (media)
ACTION=add
DEVNAME=/dev/media5
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/media5
MAJOR=509
MINOR=5
SEQNUM=24416
SUBSYSTEM=media
USEC_INITIALIZED=5662716433110

UDEV  [5662716.435400] bind     /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.1 (usb)
ACTION=bind
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.1
DEVTYPE=usb_interface
DRIVER=uvcvideo
ID_USB_CLASS_FROM_DATABASE=Miscellaneous Device
ID_USB_PROTOCOL_FROM_DATABASE=Interface Association
ID_VENDOR_FROM_DATABASE=GEMBIRD
INTERFACE=14/2/0
MODALIAS=usb:v1908p2311d0100dcEFdsc02dp01ic0Eisc02ip00in01
PRODUCT=1908/2311/100
SEQNUM=24421
SUBSYSTEM=usb
TYPE=239/2/1
USEC_INITIALIZED=5662716430425

UDEV  [5662716.436539] add      /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/video4linux/video0 (video4linux)
ACTION=add
COLORD_DEVICE=1
COLORD_KIND=camera
DEVLINKS=/dev/v4l/by-id/usb-Generic_USB2.0_PC_CAMERA-video-index0 /dev/v4l/by-path/pci-0000:00:14.0-usb-0:5.2.1:1.0-video-index0
DEVNAME=/dev/video0
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/video4linux/video0
ID_BUS=usb
ID_FOR_SEAT=video4linux-pci-0000_00_14_0-usb-0_5_2_1_1_0
ID_MODEL=USB2.0_PC_CAMERA
ID_MODEL_ENC=USB2.0\x20PC\x20CAMERA
ID_MODEL_ID=2311
ID_PATH=pci-0000:00:14.0-usb-0:5.2.1:1.0
ID_PATH_TAG=pci-0000_00_14_0-usb-0_5_2_1_1_0
ID_REVISION=0100
ID_SERIAL=Generic_USB2.0_PC_CAMERA
ID_TYPE=video
ID_USB_DRIVER=uvcvideo
ID_USB_INTERFACES=:0e0100:0e0200:
ID_USB_INTERFACE_NUM=00
ID_V4L_CAPABILITIES=:capture:
ID_V4L_PRODUCT=USB2.0 PC CAMERA: USB2.0 PC CAM
ID_V4L_VERSION=2
ID_VENDOR=Generic
ID_VENDOR_ENC=Generic
ID_VENDOR_ID=1908
MAJOR=81
MINOR=0
SEQNUM=24415
SUBSYSTEM=video4linux
TAGS=:seat:uaccess:
USEC_INITIALIZED=5662716436054

UDEV  [5662716.436956] add      /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121 (input)
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121
EV=3
ID_BUS=usb
ID_FOR_SEAT=input-pci-0000_00_14_0-usb-0_5_2_1_1_0
ID_INPUT=1
ID_INPUT_KEY=1
ID_MODEL=USB2.0_PC_CAMERA
ID_MODEL_ENC=USB2.0\x20PC\x20CAMERA
ID_MODEL_ID=2311
ID_PATH=pci-0000:00:14.0-usb-0:5.2.1:1.0
ID_PATH_TAG=pci-0000_00_14_0-usb-0_5_2_1_1_0
ID_REVISION=0100
ID_SERIAL=Generic_USB2.0_PC_CAMERA
ID_TYPE=video
ID_USB_DRIVER=uvcvideo
ID_USB_INTERFACES=:0e0100:0e0200:
ID_USB_INTERFACE_NUM=00
ID_VENDOR=Generic
ID_VENDOR_ENC=Generic
ID_VENDOR_ID=1908
KEY=100000 0 0 0
MODALIAS=input:b0003v1908p2311e0100-e0,1,kD4,ramlsfw
NAME="USB2.0 PC CAMERA: USB2.0 PC CAM"
PHYS="usb-0000:00:14.0-5.2.1/button"
PRODUCT=3/1908/2311/100
PROP=0
SEQNUM=24417
SUBSYSTEM=input
TAGS=:seat:
USEC_INITIALIZED=5662716436500

UDEV  [5662716.591160] add      /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22 (input)
ACTION=add
BACKSPACE=guess
DEVLINKS=/dev/input/by-path/pci-0000:00:14.0-usb-0:5.2.1:1.0-event /dev/input/by-id/usb-Generic_USB2.0_PC_CAMERA-event-if00
DEVNAME=/dev/input/event22
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22
ID_BUS=usb
ID_INPUT=1
ID_INPUT_KEY=1
ID_MODEL=USB2.0_PC_CAMERA
ID_MODEL_ENC=USB2.0\x20PC\x20CAMERA
ID_MODEL_ID=2311
ID_PATH=pci-0000:00:14.0-usb-0:5.2.1:1.0
ID_PATH_TAG=pci-0000_00_14_0-usb-0_5_2_1_1_0
ID_REVISION=0100
ID_SERIAL=Generic_USB2.0_PC_CAMERA
ID_TYPE=video
ID_USB_DRIVER=uvcvideo
ID_USB_INTERFACES=:0e0100:0e0200:
ID_USB_INTERFACE_NUM=00
ID_VENDOR=Generic
ID_VENDOR_ENC=Generic
ID_VENDOR_ID=1908
LIBINPUT_DEVICE_GROUP=3/1908/2311:usb-0000:00:14.0-5.2
MAJOR=13
MINOR=86
SEQNUM=24418
SUBSYSTEM=input
TAGS=:power-switch:
USEC_INITIALIZED=5662716590816
XKBLAYOUT=us,il
XKBMODEL=pc105
XKBOPTIONS=grp:alt_shift_toggle,grp_led:scroll
XKBVARIANT=,

UDEV  [5662716.593390] bind     /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0 (usb)
ACTION=bind
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0
DEVTYPE=usb_interface
DRIVER=uvcvideo
ID_USB_CLASS_FROM_DATABASE=Miscellaneous Device
ID_USB_PROTOCOL_FROM_DATABASE=Interface Association
ID_VENDOR_FROM_DATABASE=GEMBIRD
INTERFACE=14/1/0
MODALIAS=usb:v1908p2311d0100dcEFdsc02dp01ic0Eisc01ip00in00
PRODUCT=1908/2311/100
SEQNUM=24419
SUBSYSTEM=usb
TYPE=239/2/1
USEC_INITIALIZED=5662716430396

UDEV  [5662716.595836] bind     /devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1 (usb)
ACTION=bind
BUSNUM=001
DEVNAME=/dev/bus/usb/001/098
DEVNUM=098
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1
DEVTYPE=usb_device
DRIVER=usb
ID_BUS=usb
ID_MODEL=USB2.0_PC_CAMERA
ID_MODEL_ENC=USB2.0\x20PC\x20CAMERA
ID_MODEL_ID=2311
ID_REVISION=0100
ID_SERIAL=Generic_USB2.0_PC_CAMERA
ID_USB_INTERFACES=:0e0100:0e0200:
ID_VENDOR=Generic
ID_VENDOR_ENC=Generic
ID_VENDOR_FROM_DATABASE=GEMBIRD
ID_VENDOR_ID=1908
MAJOR=189
MINOR=97
PRODUCT=1908/2311/100
SEQNUM=24422
SUBSYSTEM=usb
TYPE=239/2/1
USEC_INITIALIZED=5662716427506

So the device I want to avoid was /dev/input/event22 this time. What’s its attributes?

$ sudo udevadm info -a -n /dev/input/event22 

Udevadm info starts with the device specified by the devpath and then
walks up the chain of parent devices. It prints for every device
found, all possible attributes in the udev rules key format.
A rule to match, can be composed by the attributes of the device
and the attributes from one single parent device.

  looking at device '/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22':
    KERNEL=="event22"
    SUBSYSTEM=="input"
    DRIVER==""

  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121':
    KERNELS=="input121"
    SUBSYSTEMS=="input"
    DRIVERS==""
    ATTRS{name}=="USB2.0 PC CAMERA: USB2.0 PC CAM"
    ATTRS{phys}=="usb-0000:00:14.0-5.2.1/button"
    ATTRS{properties}=="0"
    ATTRS{uniq}==""

  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0':
    KERNELS=="1-5.2.1:1.0"
    SUBSYSTEMS=="usb"
    DRIVERS=="uvcvideo"
    ATTRS{authorized}=="1"
    ATTRS{bAlternateSetting}==" 0"
    ATTRS{bInterfaceClass}=="0e"
    ATTRS{bInterfaceNumber}=="00"
    ATTRS{bInterfaceProtocol}=="00"
    ATTRS{bInterfaceSubClass}=="01"
    ATTRS{bNumEndpoints}=="01"
    ATTRS{iad_bFirstInterface}=="00"
    ATTRS{iad_bFunctionClass}=="0e"
    ATTRS{iad_bFunctionProtocol}=="00"
    ATTRS{iad_bFunctionSubClass}=="03"
    ATTRS{iad_bInterfaceCount}=="02"
    ATTRS{interface}=="USB2.0 PC CAMERA"
    ATTRS{supports_autosuspend}=="1"

  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1':
    KERNELS=="1-5.2.1"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb"
    ATTRS{authorized}=="1"
    ATTRS{avoid_reset_quirk}=="0"
    ATTRS{bConfigurationValue}=="1"
    ATTRS{bDeviceClass}=="ef"
    ATTRS{bDeviceProtocol}=="01"
    ATTRS{bDeviceSubClass}=="02"
    ATTRS{bMaxPacketSize0}=="64"
    ATTRS{bMaxPower}=="256mA"
    ATTRS{bNumConfigurations}=="1"
    ATTRS{bNumInterfaces}==" 2"
    ATTRS{bcdDevice}=="0100"
    ATTRS{bmAttributes}=="80"
    ATTRS{busnum}=="1"
    ATTRS{configuration}==""
    ATTRS{devnum}=="98"
    ATTRS{devpath}=="5.2.1"
    ATTRS{idProduct}=="2311"
    ATTRS{idVendor}=="1908"
    ATTRS{ltm_capable}=="no"
    ATTRS{manufacturer}=="Generic"
    ATTRS{maxchild}=="0"
    ATTRS{product}=="USB2.0 PC CAMERA"
    ATTRS{quirks}=="0x0"
    ATTRS{removable}=="unknown"
    ATTRS{speed}=="480"
    ATTRS{urbnum}=="16"
    ATTRS{version}==" 2.00"

  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2':
    KERNELS=="1-5.2"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb"
    ATTRS{authorized}=="1"
    ATTRS{avoid_reset_quirk}=="0"
    ATTRS{bConfigurationValue}=="1"
    ATTRS{bDeviceClass}=="09"
    ATTRS{bDeviceProtocol}=="01"
    ATTRS{bDeviceSubClass}=="00"
    ATTRS{bMaxPacketSize0}=="64"
    ATTRS{bMaxPower}=="100mA"
    ATTRS{bNumConfigurations}=="1"
    ATTRS{bNumInterfaces}==" 1"
    ATTRS{bcdDevice}=="0100"
    ATTRS{bmAttributes}=="e0"
    ATTRS{busnum}=="1"
    ATTRS{configuration}==""
    ATTRS{devnum}=="75"
    ATTRS{devpath}=="5.2"
    ATTRS{idProduct}=="7250"
    ATTRS{idVendor}=="214b"
    ATTRS{ltm_capable}=="no"
    ATTRS{maxchild}=="4"
    ATTRS{product}=="USB2.0 HUB"
    ATTRS{quirks}=="0x0"
    ATTRS{removable}=="unknown"
    ATTRS{speed}=="480"
    ATTRS{urbnum}=="409"
    ATTRS{version}==" 2.00"

  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-5':
    KERNELS=="1-5"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb"
    ATTRS{authorized}=="1"
    ATTRS{avoid_reset_quirk}=="0"
    ATTRS{bConfigurationValue}=="1"
    ATTRS{bDeviceClass}=="09"
    ATTRS{bDeviceProtocol}=="02"
    ATTRS{bDeviceSubClass}=="00"
    ATTRS{bMaxPacketSize0}=="64"
    ATTRS{bMaxPower}=="0mA"
    ATTRS{bNumConfigurations}=="1"
    ATTRS{bNumInterfaces}==" 1"
    ATTRS{bcdDevice}=="0123"
    ATTRS{bmAttributes}=="e0"
    ATTRS{busnum}=="1"
    ATTRS{configuration}==""
    ATTRS{devnum}=="73"
    ATTRS{devpath}=="5"
    ATTRS{idProduct}=="5411"
    ATTRS{idVendor}=="0bda"
    ATTRS{ltm_capable}=="no"
    ATTRS{manufacturer}=="Generic"
    ATTRS{maxchild}=="4"
    ATTRS{product}=="4-Port USB 2.0 Hub"
    ATTRS{quirks}=="0x0"
    ATTRS{removable}=="removable"
    ATTRS{speed}=="480"
    ATTRS{urbnum}=="69"
    ATTRS{version}==" 2.10"

  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1':
    KERNELS=="usb1"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb"
    ATTRS{authorized}=="1"
    ATTRS{authorized_default}=="1"
    ATTRS{avoid_reset_quirk}=="0"
    ATTRS{bConfigurationValue}=="1"
    ATTRS{bDeviceClass}=="09"
    ATTRS{bDeviceProtocol}=="01"
    ATTRS{bDeviceSubClass}=="00"
    ATTRS{bMaxPacketSize0}=="64"
    ATTRS{bMaxPower}=="0mA"
    ATTRS{bNumConfigurations}=="1"
    ATTRS{bNumInterfaces}==" 1"
    ATTRS{bcdDevice}=="0415"
    ATTRS{bmAttributes}=="e0"
    ATTRS{busnum}=="1"
    ATTRS{configuration}==""
    ATTRS{devnum}=="1"
    ATTRS{devpath}=="0"
    ATTRS{idProduct}=="0002"
    ATTRS{idVendor}=="1d6b"
    ATTRS{interface_authorized_default}=="1"
    ATTRS{ltm_capable}=="no"
    ATTRS{manufacturer}=="Linux 4.15.0-20-generic xhci-hcd"
    ATTRS{maxchild}=="16"
    ATTRS{product}=="xHCI Host Controller"
    ATTRS{quirks}=="0x0"
    ATTRS{removable}=="unknown"
    ATTRS{serial}=="0000:00:14.0"
    ATTRS{speed}=="480"
    ATTRS{urbnum}=="454"
    ATTRS{version}==" 2.00"

  looking at parent device '/devices/pci0000:00/0000:00:14.0':
    KERNELS=="0000:00:14.0"
    SUBSYSTEMS=="pci"
    DRIVERS=="xhci_hcd"
    ATTRS{broken_parity_status}=="0"
    ATTRS{class}=="0x0c0330"
    ATTRS{consistent_dma_mask_bits}=="64"
    ATTRS{d3cold_allowed}=="1"
    ATTRS{dbc}=="disabled"
    ATTRS{device}=="0xa2af"
    ATTRS{dma_mask_bits}=="64"
    ATTRS{driver_override}=="(null)"
    ATTRS{enable}=="1"
    ATTRS{irq}=="33"
    ATTRS{local_cpulist}=="0-11"
    ATTRS{local_cpus}=="0,00000000,00000fff"
    ATTRS{msi_bus}=="1"
    ATTRS{numa_node}=="0"
    ATTRS{revision}=="0x00"
    ATTRS{subsystem_device}=="0x5007"
    ATTRS{subsystem_vendor}=="0x1458"
    ATTRS{vendor}=="0x8086"

  looking at parent device '/devices/pci0000:00':
    KERNELS=="pci0000:00"
    SUBSYSTEMS==""
    DRIVERS==""

And what udev rules are currently in effect for this? Note that this doesn’t require root, and nothing really happens to the system:

$ udevadm test -a add $(udevadm info -q path -n /dev/input/event22)calling: test
version 237
This program is for debugging only, it does not run any program
specified by a RUN key. It may show incorrect results, because
some values may be different, or not available at a simulation run.

Load module index
Parsed configuration file /etc/systemd/network/eth1.link
Skipping empty file: /etc/systemd/network/99-default.link
Created link configuration context.

[ ... reading a lot of files ... ]

rules contain 393216 bytes tokens (32768 * 12 bytes), 39371 bytes strings
25632 strings (220044 bytes), 22252 de-duplicated (184054 bytes), 3381 trie nodes used
GROUP 104 /lib/udev/rules.d/50-udev-default.rules:29
IMPORT builtin 'hwdb' /lib/udev/rules.d/60-evdev.rules:8
IMPORT builtin 'hwdb' returned non-zero
IMPORT builtin 'hwdb' /lib/udev/rules.d/60-evdev.rules:17
IMPORT builtin 'hwdb' returned non-zero
IMPORT builtin 'hwdb' /lib/udev/rules.d/60-evdev.rules:21
IMPORT builtin 'hwdb' returned non-zero
IMPORT builtin 'input_id' /lib/udev/rules.d/60-input-id.rules:5
capabilities/ev raw kernel attribute: 3
capabilities/abs raw kernel attribute: 0
capabilities/rel raw kernel attribute: 0
capabilities/key raw kernel attribute: 100000 0 0 0
properties raw kernel attribute: 0
test_key: checking bit block 0 for any keys; found=0
test_key: checking bit block 64 for any keys; found=0
test_key: checking bit block 128 for any keys; found=0
test_key: checking bit block 192 for any keys; found=1
IMPORT builtin 'hwdb' /lib/udev/rules.d/60-input-id.rules:6
IMPORT builtin 'hwdb' returned non-zero
IMPORT builtin 'usb_id' /lib/udev/rules.d/60-persistent-input.rules:11
/sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0: if_class 14 protocol 0
LINK 'input/by-id/usb-Generic_USB2.0_PC_CAMERA-event-if00' /lib/udev/rules.d/60-persistent-input.rules:32
IMPORT builtin 'path_id' /lib/udev/rules.d/60-persistent-input.rules:35
LINK 'input/by-path/pci-0000:00:14.0-usb-0:5.2.1:1.0-event' /lib/udev/rules.d/60-persistent-input.rules:40
PROGRAM 'libinput-device-group /sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22' /lib/udev/rules.d/80-libinput-device-groups.rules:7
starting 'libinput-device-group /sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22'
'libinput-device-group /sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22'(out) '3/1908/2311:usb-0000:00:14.0-5.2'
Process 'libinput-device-group /sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22' succeeded.
IMPORT builtin 'hwdb' /lib/udev/rules.d/90-libinput-model-quirks.rules:46
IMPORT builtin 'hwdb' returned non-zero
IMPORT builtin 'hwdb' /lib/udev/rules.d/90-libinput-model-quirks.rules:50
IMPORT builtin 'hwdb' returned non-zero
handling device node '/dev/input/event22', devnum=c13:86, mode=0660, uid=0, gid=104
preserve permissions /dev/input/event22, 020660, uid=0, gid=104
preserve already existing symlink '/dev/char/13:86' to '../input/event22'
found 'c13:86' claiming '/run/udev/links/\x2finput\x2fby-id\x2fusb-Generic_USB2.0_PC_CAMERA-event-if00'
found 'c13:85' claiming '/run/udev/links/\x2finput\x2fby-id\x2fusb-Generic_USB2.0_PC_CAMERA-event-if00'
found 'c13:84' claiming '/run/udev/links/\x2finput\x2fby-id\x2fusb-Generic_USB2.0_PC_CAMERA-event-if00'
found 'c13:83' claiming '/run/udev/links/\x2finput\x2fby-id\x2fusb-Generic_USB2.0_PC_CAMERA-event-if00'
creating link '/dev/input/by-id/usb-Generic_USB2.0_PC_CAMERA-event-if00' to '/dev/input/event22'
preserve already existing symlink '/dev/input/by-id/usb-Generic_USB2.0_PC_CAMERA-event-if00' to '../event22'
found 'c13:86' claiming '/run/udev/links/\x2finput\x2fby-path\x2fpci-0000:00:14.0-usb-0:5.2.1:1.0-event'
found 'c13:85' claiming '/run/udev/links/\x2finput\x2fby-path\x2fpci-0000:00:14.0-usb-0:5.2.1:1.0-event'
found 'c13:84' claiming '/run/udev/links/\x2finput\x2fby-path\x2fpci-0000:00:14.0-usb-0:5.2.1:1.0-event'
found 'c13:83' claiming '/run/udev/links/\x2finput\x2fby-path\x2fpci-0000:00:14.0-usb-0:5.2.1:1.0-event'
creating link '/dev/input/by-path/pci-0000:00:14.0-usb-0:5.2.1:1.0-event' to '/dev/input/event22'
preserve already existing symlink '/dev/input/by-path/pci-0000:00:14.0-usb-0:5.2.1:1.0-event' to '../event22'
ACTION=add
BACKSPACE=guess
DEVLINKS=/dev/input/by-path/pci-0000:00:14.0-usb-0:5.2.1:1.0-event /dev/input/by-id/usb-Generic_USB2.0_PC_CAMERA-event-if00
DEVNAME=/dev/input/event22
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.2/1-5.2.1/1-5.2.1:1.0/input/input121/event22
ID_BUS=usb
ID_INPUT=1
ID_INPUT_KEY=1
ID_MODEL=USB2.0_PC_CAMERA
ID_MODEL_ENC=USB2.0\x20PC\x20CAMERA
ID_MODEL_ID=2311
ID_PATH=pci-0000:00:14.0-usb-0:5.2.1:1.0
ID_PATH_TAG=pci-0000_00_14_0-usb-0_5_2_1_1_0
ID_REVISION=0100
ID_SERIAL=Generic_USB2.0_PC_CAMERA
ID_TYPE=video
ID_USB_DRIVER=uvcvideo
ID_USB_INTERFACES=:0e0100:0e0200:
ID_USB_INTERFACE_NUM=00
ID_VENDOR=Generic
ID_VENDOR_ENC=Generic
ID_VENDOR_ID=1908
LIBINPUT_DEVICE_GROUP=3/1908/2311:usb-0000:00:14.0-5.2
MAJOR=13
MINOR=86
SUBSYSTEM=input
TAGS=:power-switch:
USEC_INITIALIZED=5662716590816
XKBLAYOUT=us,il
XKBMODEL=pc105
XKBOPTIONS=grp:alt_shift_toggle,grp_led:scroll
XKBVARIANT=,
Unload module index
Unloaded link configuration context.

Other failed attempts

I tried the following:

# Rule for disabling bogus keyboard on webcam. It causes X-Windows to
# crash if it goes on and off too much

SUBSYSTEM=="input", ENV{ID_VENDOR_ID}=="1908", ENV{ID_MODEL_ID}=="2311", MODE:="000"
SUBSYSTEM=="input", ATTRS{name}=="USB2.0 PC CAMERA:*", ENV{LIBINPUT_IGNORE_DEVICE}="1"

(the := assignment makes this assignment final).

However none of these two rules managed to stop X from reacting.

Setting the mode to 000 made the device file inaccessible, but yet it was registered. As for the second rule, it doesn’t help, because it indeed set LIBINPUT_IGNORE_DEVICE correctly, but for the wrong udev event. That’s because the udev event that triggers libinput is based upon that the KERNEL attribute is event[0-9]*, which is executed earlier (see 80-libinput-device-groups.rules), but ATTRS{name} isn’t defined for that specific udev event (see output of udevadm info above).

I also tried RUN+=”/bin/rm /dev/input/event%n”, and that indeed removed the device node, but X still reacted, and complained with “libinput: USB2.0 PC CAMERA: USB2.0 PC CAM: Failed to create a device for /dev/input/event28″. Because it was indeed deleted.

But since it appears like X.org accesses keyboards through libinput, maybe use the example for ignoring a device, as given on this page, even though it’s quite similar to what I’ve already attempted?

So I saved this file as /etc/udev/rules.d/79-no-camera-keyboard.rules:

# Make libinput ignore webcam's button as a keyboard. As a result there's
# no event to X-Windows

ACTION=="add|change", KERNEL=="event[0-9]*", \
   ENV{ID_VENDOR_ID}=="1908", \
   ENV{ID_MODEL_ID}=="2311", \
   ENV{LIBINPUT_IGNORE_DEVICE}="1"

And then reload:

# udevadm control --reload

but that didn’t make any apparent difference (I verified that the rule was matched).

And that’s all, folks. Recall that I didn’t promise a happy end.