# Rules for monitors implementing USB communication with their Virtual Control Panel. 

# This sample file can be modified and copied to /etc/udev/rules.d.  

# If file /etc/udev/rules.d/60-ddcutil-usb.rules exists, it overrides a file with
# the same name in /usr/lib/udev/rules.d.  (This file used to be created by ddcutil 
# installation.)

# The simplest solution is to specify a particular monitor device by its vid/pid, 
# and then use TAG+="uaccess" to grant the current user read/write access to it.
# The values in this example are for an Apple Cinema Display, model A1082:
# SUBSYSTEM=="usbmisc", ATTRS{idVendor}=="05ac", ATTRS{idProduct}=="9223", TAG+="uaccess" 

# A more general solution is to use ddcutil chkusbmon to check if a USB Human
# Interface device implements the USB Device Class Definition for Human Interface
# Devices. Unfortunately, this has been seen to cause system instability in 
# certain ill-defined cases.

# Note this rule may  have to be adjusted to reflect the actual path where 
# ddcutil is installed.  The -v option produces informational messages.
# These are lost when the rule is normally executed by udev, but can be 
# helpful when rules are tested using the "udevadm test" command. 
# SUBSYSTEM=="usbmisc",  KERNEL=="hiddev*", PROGRAM="/usr/bin/ddcutil chkusbmon $env{DEVNAME} -v", TAG+="uaccess"