#!/bin/sh -e

### BEGIN INIT INFO
# Provides:          udev-cache
# Required-Start:    mountall
# Required-Stop:
# Default-Start:     S
# Default-Stop:
# Short-Description: cache /dev to speedup the udev next boot
### END INIT INFO

export TZ=/etc/localtime

[ -r /proc/mounts ] || exit 1
[ -x @UDEVD@ ] || exit 1
[ -d /sys/class ] || exit 1

[ -f /etc/default/rcS ] && . /etc/default/rcS
DEVCACHE_TMP="/dev/shm/udev-cache-tmp.tar"
SYSCONF_CACHED="/etc/udev/cache.data"
SYSCONF_TMP="/dev/shm/udev.cache"

# A list of files which are used as a criteria to judge whether the udev cache could be reused.
CMP_FILE_LIST="/proc/version /proc/cmdline /proc/devices /proc/atags"
[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache

readfiles () {
   READDATA=""
   for filename in $@; do
	   if [ -r $filename ]; then
		   while read line; do
			   READDATA="$READDATA$line"
		   done < $filename
	   fi
   done
}

if [ "$ROOTFS_READ_ONLY" = "yes" ]; then
    [ "$VERBOSE" != "no" ] && echo "udev-cache: read-only rootfs, skip generating udev-cache"
    exit 0
fi

if [ "$DEVCACHE" != "" -a -e "$SYSCONF_TMP" ]; then
	echo "Populating dev cache"
	udevadm control --stop-exec-queue
	readfiles $CMP_FILE_LIST
	echo "$READDATA" > "$SYSCONF_TMP"
	find /dev -xdev \( -type b -o -type c -o -type l \) | cut -c 2- \
		| xargs tar cf "${DEVCACHE_TMP}" -T-
	gzip < "${DEVCACHE_TMP}" > "$DEVCACHE"
	rm -f "${DEVCACHE_TMP}"
	mv "$SYSCONF_TMP" "$SYSCONF_CACHED"
	udevadm control --start-exec-queue
fi

exit 0