initrd/init:find_onepupdrv() (tahrpup)

find_onepupdrv() {  Line 288 of initrd/init
# "$1" - partition - ex: sda3
# "$2" - specified filename - ex: /pup/mydrv-1.2.3.sfs
# "$3" - default filename - ex: adrv_tahr_6.0.5.sfs
# "$4" - prefix for "drv" mountpoint - ex: a
 ONE_FN=""
 [ "${2}" ] || [ "${3}" ] || return
 [ "${4}" ] || return
 if [ "${1}" ];then
  ONE_PART="${1}"
 else
  ONE_PART="$P_PART"
 fi
 [ "$ONE_PART" ] || return
 ensure_mounted "$ONE_PART" "/mnt/${4}drv"
 [ "$ONE_MP" ] || return
 find_drv_file "${2}" "${3}"
 [ "$ONE_FN" = "" -a "${2}" ] && echo "$ONE_PART, $ONE_TRY_FN file not found."
}