#!/bin/sh
#
# Create a systemd environment file for tee-supplicant
# $1 is the path to the file to be generated.
# At the moment this figures out the --rpmb-cid parameter to be given to
# tee-supplicant, indicating which eMMC device OP-TEE should use for RPMB
# storage.
# No file is generated if no device is found (not an error) or if multiple
# eMMCs are found (which is an error).

[ "$1" ] || { echo Usage: $0 FILE >&2; exit 1; }

touch $1

for f in /sys/class/mmc_host/mmc*/mmc*\:*/mmcblk?rmpb; do
  [ "$CID" ] && { echo $0: Multiple eMMC devices found, not chosing one automatically >&2; exit 2; }
  # POSIX shells don't expand globbing patterns that match no file
  [ -e $f ] || exit 0
  CID=$(cat $(dirname $f)/cid)
done
[ "$CID" ] && echo RPMB_CID="--rpmb-cid $CID" >$1