Static /dev/input entry for bluetooth controllers

[jmbooth2000]

It was bugging that depending on what USB devices were installed my bluetooth PS3 controllers would get a different /dev/input/event<n> assignment. The joystick selection script helps but didn't seem to be the right way to handle the problem and didn't work very well with some of the emulators.

What I created instead was a way to use a udev rule to create a static ps3_controller_event1 link to whatever /dev/input/event<n> was assigned. This way I can pick exactly what controller I want to use and don't have to worry about the order. This technique also works with other controller types.

I did a pile of research and didn't find any existing solutions. The closest I found were a couple of entries that said it wasn't possible. The following are my instruction on how to do this.

First create a new udev rule using the following,

sudo nano /etc/udev/rules.d/99-xxx_map_controllers.rules

containing the following,

ATTRS{name}=="PLAYSTATION(R)3 Controller", PROGRAM="/bin/ps3_dev_namer %k", SYMLINK+="%c"

The first part of this looks for a udev assignment that matches ATTRS{name}=="PLAYSTATION(R)3 Controller". This occurs whenever your connect a PS3 controller. If you aren’t using ps3 controllers you can modify this to search for your controller identity by using the “udevadm info -a -n /dev/input/event1” command and finding the corresponding string for your controller.

The second part defines the actions that should be taken when a PS3 controller is attached. In this case the PROGRAM="/bin/ps3_dev_namer %k” section calls the /dev/ps3_dev_namer script I created. This script iterates through the potential /dev/input/ps3_controller_event<n> devices and returns the first unassigned device. So on the first call it will return /dev/input/ps3_controller_event1. The SYMLINK+="%c" section creates a “/dev/input/ps3_controller_event1” entry that links to whatever /dev/input/event<n> was assigned to the first PS3 controller that was connected. Connecting the next PS3 controller will create a “/dev/input/ps3_controller_event2” entry that points to its appropriate event. This means that you can use the /dev/input/ps3_controller_event<n> entries you can use in your emulator config files.

#!/bin/bash
# /bin/ps3_dev_namer script to provide a static name for ps3 controllers 
# Created by Jonathan Booth ©2018 free for use providing this line remains
# Called by udev rule to create static device entries that link to the dynamically /dev/input/event<n>
# This  is useful when the device order changes but you need a static way to refer to the same device 
# I use this is retropie to create a static mapping for my ps3 controller events and joysticks
#
# To use this script create “/etc/udev/rules.d/99-xxx_map_controllers.rules” with the following line
# less the leading ‘#” character
# ATTRS{name}=="PLAYSTATION(R)3 Controller", PROGRAM="/bin/device_namer %k", SYMLINK+="%c"

BASENAME="/dev/input/ps3_controller"	# Change if you have a different controller
COUNT=1

if [[ $1 == js* ]]			# if we have a js<n> device		
then
        TYPE="_js"			# Append “_js”
elif [[ $1 == event* ]]		# else if we have an event<n> device
then
        TYPE="_event"		# Append “_event”
fi

while [ $COUNT -le 100 ]                # Main loop with backup plan to exit after 100 trys. 
do
        NAME="$BASENAME$COUNT$TYPE"     # Build filename to test for

        if [ -e $NAME ]                 	# if the file exists
        then
                ((COUNT+=1))            	# increment count and try the next possible entry
        else                            		# file does not exist
                echo $NAME | cut -c 6-  # output the name of the first available link less the "\dev" prefix
                break                   	# break the loop and exit
        fi
done

I was pretty happy when I got this working as the combination of a keyboard, trackpad, trackball, 2 arcade controllers, 2 wii controllers, 2 old style usb controllers, and 2 PS3 controllers was driving me nuts every time I changed the order. Now I can create rules to create static named /dev/input devices that point to whatever the assigned /dev/input/event was.

I hope this will be of use to others and I hope people will update this thread on how they use it.