Script to enable/disable USB keyboard support on the Remarkable 2

rm-keyboard.sh

#!/bin/bash

# Script to enable/disable USB keyboard support on the remarkable 2.
# Just copy it to the rm2 over SSH, make it executable with chmod +x, and run it.
# You can confirm the change using `lsusb`. When this is enabled, you will see the host device and anything
# plugged into it.
#
# Then connect your keyboard using a powered USB OTG adapter. Bonus: the RM2 will charge while using it.
# In theory it is safe to keep "enabled" all the time, but TMK this has not been tested. It probably impacts battery life. 

# All credit to https://github.com/dps/remarkable-keywriter/issues/14#issuecomment-1223341129

# This script is provided as-is, no warranty is provided or implied. This script may hide your keys, anger your roommates,
# teach your pets to poop on your furniture, or do other awful things and IT'S NOT MY FAULT.

# Usage: rm-keyboard.sh {enable|disable}

# Check if the script is being run with root privileges.
if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root" 
   exit 1
fi

# Function to display usage information.
usage() {
  echo "Usage: $0 {enable|disable}"
  exit 2
}

# Check command line arguments.
if [ "$#" -ne 1 ]; then
    usage
fi

ROLE_FILE="/sys/kernel/debug/ci_hdrc.0/role"

# Check if the role file exists.
if [ ! -f "$ROLE_FILE" ]; then
    echo "The role file $ROLE_FILE does not exist. Ensure your system has the ci_hdrc module enabled."
    exit 3
fi

# Toggle the USB role based on the argument.
case "$1" in
    enable)
        echo "host" > "$ROLE_FILE"
        echo "Enabled: USB role set to host."
        ;;
    disable)
        echo "gadget" > "$ROLE_FILE"
        echo "Disabled: USB role set to gadget."
        ;;
    *)
        usage
        ;;
esac

exit 0