fs/skeleton/bin/wait-scsi

#!/bin/sh
#
# Wait up to a few seconds for each hotplug-detected SCSI interface to have
# at least one hotplug-detected disk attached.  This includes usb-storage
# and SATA.
#
# The assumption that if any device is present, the polling of that SCSI bus
# is finished, is probably not 100% valid, but it should be pretty close,
# especially in the modern world where every disk always seems to get its
# own bus anyway.
#
NUM_PROBES=6
PROBE_DELAY_SECS=.5

# If this is non-empty, only matches scsi hosts that contain the given
# name prefix in their path (example: usb)
TYPE=$1

. /etc/utils.sh

realdir() {
  # should not need to set PWD=, but our /bin/pwd implementation seems
  # to use it, unlike the normal Linux one.
  (cd "$1" && PWD= /bin/pwd)
}


: >>/tmp/wait-scsi.done

# capture the list of hosts once at the start, in case new interfaces arrive
# during our probe; we don't want to give them a partial timeout, so we'll
# ignore them entirely for this run.
for hostpath in /sys/bus/scsi/devices/host*; do
  [ -e "$hostpath" ] || continue
  hostpath=$(realdir "$hostpath")
  if [ -n "$TYPE" ] && ! contains "$hostpath" "/$TYPE"; then
    continue
  fi
  hostpaths="$hostpaths $hostpath"
  echo "wait-scsi: $hostpath" >&2
done

for timeout in $(seq "$NUM_PROBES"); do
  ok=1
  for hostpath in $hostpaths; do
    [ -e "$hostpath" ] || continue
    hostpath=$(realdir "$hostpath")
    if grep -q "$hostpath" /tmp/wait-scsi.done; then
      # another running instance might have finished polling this
      # interface while we were here; if it timed out this interface
      # already, then we don't need to poll it anymore.
      continue
    fi
    found=
    for d in /sys/block/sd*; do
      [ -e "$d" ] || continue
      devpath=$(realdir "$d/device")
      if startswith "$devpath" "$hostpath"; then
        found=1
        break
      fi
    done
    # if any host doesn't have a device attached, we're not done yet.
    [ -z "$found" ] && ok=
  done
  [ "$ok" = 1 ] && break
  sleep "$PROBE_DELAY_SECS"
done

# We've waited for these hosts already, no need to wait again later
for d in $hostpaths; do
  echo "$d"
done >>/tmp/wait-scsi.done