egpu

#!/bin/bash

set -o errexit # exit script if a command fails
set -o nounset # exit when trying to use undeclared variables

# define the configs you manualy put there for xorg
declare INTERNAL=/etc/X11/xorg.conf.internal
declare EXTERNAL=/etc/X11/xorg.conf.egpu
# xorg default config file will be linked to one of the above
# ensure you do not have any nvidia config in /etc/X11/xorg.conf.d/ at this moment. 
# this cost me half an hour
declare LINK=/etc/X11/xorg.conf

# egpu device state
declare egpu_connected=0

# returns 1 if egpu is connected, 0 if not
function is_egpu_connected() {

	# read pci id from xorg.conf.egpu
	declare egpu_pci_id=$(cat $EXTERNAL | grep -Ei "BusID" | grep -oEi '[0-9]+\:[0-9]+\:[0-9]+')

	# create an array by splitting the BUS-ID on ':'
	declare busArray=(${egpu_pci_id//:/ })
	declare bus1d=${busArray[0]}
	declare bus2d=${busArray[1]}
	declare bus3d=${busArray[2]}

	# convert dec to hex
	declare bus1h=$(printf "%02x" $bus1d)
	declare bus2h=$(printf "%02x" $bus2d)
	declare bus3h=$(printf "%01x" $bus3d)

	if [ $(lspci | grep -iEc "$bus1h:$bus2h.$bus3h") -eq 1 ]; then
		echo "EGPU is connected."
		egpu_connected=1
	else
		echo "EGPU is disconnected."
		egpu_connected=0
	fi
}


function unlink_config() {
	if test -L $LINK; then
	    sudo unlink $LINK
    fi
}

function link_config() {
	unlink_config
	sudo ln -s $1 $LINK
}

# first and only argument needs to be start or stop
if [ "$1" != "start" ] && [ "$1" != "stop" ]; then
	echo "Argument Error: first argument needs to be start/stop"
	exit 1
fi

if [ "$1" = "start" ] ; then
	echo "Setup configuration for external gpu"
	# only allow usage if an egpu is currently attachted
	is_egpu_connected
	if [ ${egpu_connected} != 1 ] ; then
		echo "Configuration Error: Plug in or change configuration"
		exit 1
	fi
	link_config $EXTERNAL
else
	# let always work using the internal gpu
	echo "Setup configuration for internal gpu"
	link_config $INTERNAL
fi
echo "configuration done"

echo "I will now restart your x-session to the desired gpu."
echo "If anthing goes wrong, you can still login to a different tty without a desktop environment and fix it."

echo "I will restart X in 3 seconds"
sleep 3
sudo systemctl restart display-manager.service

exit 0