usb-port-to-pci.sh

#!/usr/bin/env bash
set -euo pipefail

# usb-port-to-pci.sh
# Map a USB device/port to the backing PCI USB controller (BDF like 0000:03:00.0).
# Usage:
#   ./usb-port-to-pci.sh --watch
#   ./usb-port-to-pci.sh 1:3          # BUS:DEV from `lsusb`
#   ./usb-port-to-pci.sh 046d:c332    # VID:PID from `lsusb`
#   ./usb-port-to-pci.sh --bus 1      # show which PCI controller owns USB bus 1
#
# Tip: run with sudo for best results (some sysfs is root-readable).

is_pci_dir() {
  local d="$1"
  [[ -L "$d/subsystem" && "$(readlink -f "$d/subsystem")" == "/sys/bus/pci" ]]
}

find_pcidir_for_sysfs_node() {
  # Walk up from a usb device sysfs node to its PCI parent dir
  local node="$1"
  local cur
  cur="$(readlink -f "$node")"
  while [[ "$cur" != "/" ]]; do
    if is_pci_dir "$cur"; then
      echo "$cur"
      return 0
    fi
    cur="$(dirname "$cur")"
  done
  return 1
}

describe_pcidir() {
  local pcidir="$1"
  local bdf vendor device
  bdf="$(basename "$pcidir")"
  vendor="$(sed 's/^0x//' "$pcidir/vendor" 2>/dev/null || true)"
  device="$(sed 's/^0x//' "$pcidir/device" 2>/dev/null || true)"
  echo "PCI controller: $bdf  (vendor:device ${vendor}:${device})"
  if command -v lspci >/dev/null 2>&1; then
    echo "lspci: $(lspci -nn -s "$bdf" || true)"
  fi
}

find_usb_sysfs_by_busdev() {
  local bus="${1%:*}" dev="${1#*:}"
  # Locate a usb device dir whose busnum/devnum match
  local d
  for d in /sys/bus/usb/devices/*; do
    [[ -f "$d/busnum" && -f "$d/devnum" ]] || continue
    if [[ "$(cat "$d/busnum")" == "$bus" && "$(cat "$d/devnum")" == "$dev" ]]; then
      echo "$d"
      return 0
    fi
  done
  return 1
}

find_usb_sysfs_by_vidpid() {
  local vidpid="$1"
  local vid="${vidpid%:*}" pid="${vidpid#*:}"
  vid="${vid,,}"; pid="${pid,,}"
  local d
  for d in /sys/bus/usb/devices/*; do
    [[ -f "$d/idVendor" && -f "$d/idProduct" ]] || continue
    if [[ "$(tr 'A-Z' 'a-z' < "$d/idVendor")" == "$vid" && \
          "$(tr 'A-Z' 'a-z' < "$d/idProduct")" == "$pid" ]]; then
      echo "$d"
      return 0
    fi
  done
  return 1
}

map_bus_to_pci() {
  local bus="$1"
  local root="/sys/bus/usb/devices/usb${bus}"
  if [[ ! -e "$root" ]]; then
    echo "USB bus ${bus} not found" >&2
    exit 1
  fi
  local pcidir
  pcidir="$(find_pcidir_for_sysfs_node "$root")" || {
    echo "Could not find PCI parent for USB bus ${bus}" >&2; exit 1; }
  describe_pcidir "$pcidir"
}

watch_mode() {
  echo "Watching for USB device add events… (Ctrl-C to quit)"
  udevadm monitor --kernel --subsystem-match=usb | \
  while read -r line; do
    if grep -q "add" <<<"$line"; then
      # pick the newest usb device with devpath (DEVTYPE=usb_device)
      local last
      last="$(ls -1dt /sys/bus/usb/devices/* 2>/dev/null | head -n1 || true)"
      [[ -n "$last" ]] || continue
      if [[ -f "$last/busnum" && -f "$last/devnum" ]]; then
        local bus dev pcidir
        bus="$(cat "$last/busnum")"
        dev="$(cat "$last/devnum")"
        echo
        echo "Detected device on USB ${bus}:${dev} ($(cat "$last/idVendor" 2>/dev/null):$(cat "$last/idProduct" 2>/dev/null))"
        pcidir="$(find_pcidir_for_sysfs_node "$last")" || { echo "No PCI parent found"; continue; }
        describe_pcidir "$pcidir"
      fi
    fi
  done
}

if [[ "${1:-}" == "--watch" ]]; then
  watch_mode
  exit 0
elif [[ "${1:-}" == "--bus" && -n "${2:-}" ]]; then
  map_bus_to_pci "$2"
  exit 0
elif [[ -n "${1:-}" ]]; then
  arg="$1"
  usbdir=""
  if [[ "$arg" =~ ^[0-9]+:[0-9]+$ ]]; then
    usbdir="$(find_usb_sysfs_by_busdev "$arg" || true)"
  elif [[ "$arg" =~ ^[0-9a-fA-F]{4}:[0-9a-fA-F]{4}$ ]]; then
    usbdir="$(find_usb_sysfs_by_vidpid "$arg" || true)"
  else
    echo "Unrecognized argument: $arg" >&2
    exit 2
  fi
  if [[ -z "$usbdir" ]]; then
    echo "Could not locate USB device for '$arg'." >&2
    exit 1
  fi
  pcidir="$(find_pcidir_for_sysfs_node "$usbdir")" || { echo "No PCI parent found"; exit 1; }
  echo "USB device sysfs: $usbdir"
  describe_pcidir "$pcidir"
  exit 0
fi

# Default: list every USB root bus -> PCI controller
echo "USB root buses -> PCI controllers:"
for root in /sys/bus/usb/devices/usb*; do
  [[ -f "$root/busnum" ]] || continue
  bus="$(cat "$root/busnum")"
  pcidir="$(find_pcidir_for_sysfs_node "$root" || true)"
  if [[ -n "$pcidir" ]]; then
    printf "  Bus %s -> %s\n" "$bus" "$(basename "$pcidir")"
  fi
done