udevadm

info

• Query sysfs or the udev database.
• This can be used to get properties to be used as match conditions

# by devpath
udevadm info \
  "/dev/dri/card2"

# by path syspath (relative to /sys)
udevadm info \
  --path "devices/pci0000:00/0000:00:01.1/0000:06:00.0/0000:07:01.0/0000:0a:00.0/0000:0b:01.0/0000:0c:00.0/0000:0d:00.0/0000:0e:00.0/drm/card2"

# by node or symlink name
udevadm info \
  --name "/dev/dri/card2"

# query
udevadm info \
  "/dev/dri/card1"
  --query "all" # default option
  # --query "name" # N (NAME). E.g., dri/card1
  # --query "symlink" # S (SYMLINK). E.g., dri/by-path/pci-0000:0e:00.0-card
  # --query "path" # P (PATH). E.g., /devices/pci0000:00/.../0000:0e:00.0>
  # --query "property" # E (ENV). E.g., ID_PATH=pci-0000:0e:00.0

# print the device information and all its parents
# all the properties can be used in udev rules to match the specified device
udevadm info \
  "/dev/dri/card1" \
  --attribute-walk

control

# reload udev rules
udevadm control --reload-rules && udevadm trigger

udevadm control --log-priority=debug
journalctl -f

trigger

# retrigger the device events
udevadm trigger

monitor

• Monitor udev events

udevadm monitor
udevadm monitor --subsystem-match "drm"