#!/bin/sh
####################################################################################
# This script is use to automatic start serial console once power up.
# Script enhancement has been done base on Bug YOCTO 10844.
# Configuration can be done in meta/conf/machine/*.conf variable SERIAL_CONSOLES.
# Most of the information is retrieve from /proc virtual filesystem which
# contain all the runtime system information (eg. system memory, device mount, etc).
####################################################################################

# Get active serial filename.
active_serial=$(grep "serial" /proc/tty/drivers | cut -d/ -f1 | sed "s/ *$//")

# Re-phrase input parameter from ttyS target index (ttyS1, ttyS2, ttyAMA0, etc).
runtime_tty=$(echo $2 | grep -oh '[0-9]')

# Backup $IFS.
DEFAULT_IFS=$IFS
# Customize Internal Field Separator.
IFS="$(printf '\n\t')"

for line in $active_serial; do
	# File is availability, file content current active serial target index.
	if [ -e "/proc/tty/driver/$line" ]
        then
		# File content a lot of unknown serial. We use -v to remove all unmatch and get left off.
		# Tail use to avoid 1st line included into the filter because 1st line is file description.
		activetty=$(grep -v "unknown" "/proc/tty/driver/$line" | tail -n +2 | grep -oh "^\s*\S*[0-9]")
		for active in $activetty; do
			# Check if both index is match then proceed to enable the serial console.
			if [ $active -eq $runtime_tty ]
			then
				if [ -c /dev/$2 ]
				then
				    /sbin/getty -L $1 $2 $3
				fi
				break
			fi
		done
	fi
done

# Restore $IFS.
IFS=$DEFAULT_IFS