PCIe Extended Tag Control

This script uses setpci to enable or disable PCI express extended tags on the specified device.

#!/bin/bash
 
dev=$1
en=$2
 
if [ -z "$dev" ]; then
    echo "Error: no device specified"
    exit 1
fi
 
if [ -z "$en" ]; then
    echo "Error: must specify operation"
    exit 1
fi
 
if [ ! -e "/sys/bus/pci/devices/$dev" ]; then
    dev="0000:$dev"
fi
 
if [ ! -e "/sys/bus/pci/devices/$dev" ]; then
    echo "Error: device $dev not found"
    exit 1
fi
 
ctrl=$(setpci -s $dev CAP_EXP+8.w)
 
if (($en > 0)); then
 
    echo "Enabling ext tag on $dev..."
 
    echo "Device control:" $ctrl
 
    setpci -s $dev CAP_EXP+8.w=$(printf "%04x" $(("0x$ctrl" | 0x0100)))
 
else
 
    echo "Disabling ext tag on $dev..."
 
    echo "Device control:" $ctrl
 
    setpci -s $dev CAP_EXP+8.w=$(printf "%04x" $(("0x$ctrl" & ~0x0100)))
 
fi