#!/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"
DEVCACHE_REGEN="/dev/shm/udev-regen" # create to request cache regen

# 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"
[ -f /proc/atags ] && CMP_FILE_LIST="$CMP_FILE_LIST /proc/atags"

# List of files whose metadata (size/mtime/name) will be included in cached
# system state.
META_FILE_LIST="lib/udev/rules.d/* etc/udev/rules.d/*"

# Command to compute system configuration.
sysconf_cmd () {
	cat -- $CMP_FILE_LIST
	stat -L -c '%s %Y %n' -- $META_FILE_LIST | awk -F/ '{print $1 " " $NF;}'
}

[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache

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

[ "$DEVCACHE" != "" ] || exit 0
[ "${VERBOSE}" == "no" ] || echo -n "udev-cache: checking for ${DEVCACHE_REGEN}... "
if ! [ -e "$DEVCACHE_REGEN" ]; then
	[ "${VERBOSE}" == "no" ] || echo "not found."
	exit 0
fi
[ "${VERBOSE}" == "no" ] || echo "found."
echo "Populating dev cache"

(
	set -e
	trap 'echo "udev-cache: update failed!"' EXIT
	udevadm control --stop-exec-queue
	sysconf_cmd > "$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
	rm -f "$DEVCACHE_REGEN"
	trap - EXIT
) &

exit 0
