Allwinner A20 CEC control script

a20_cec_ctl.sh

#!/bin/bash

# Nasty script to poke the CEC control memory locations in Allwinner A20

# Find the STANDBY_VALUE we want
case $1 in
	on)
		STANDBY_VALUE=0
		;;
	off)
		STANDBY_VALUE=1
		;;
	*)
		echo Usage: $0 "[on|off]"
		exit 1
		;;
esac


# Find the offset of cec_count
CEC_COUNT_OFFSET=$((16#`grep cec_count /proc/kallsyms  | cut -d ' ' -f 1`))
[ $CEC_COUNT_OFFSET == 0 ] && {
	echo Cannot find cec_count kernel symbol
	exit 2
}


# Find the offset of cec_standby
CEC_STANDBY_OFFSET=$((16#`grep cec_standby /proc/kallsyms  | cut -d ' ' -f 1`))
[ $CEC_STANDBY_OFFSET == 0 ] && {
        echo Cannot find cec_standby kernel symbol
        exit 3
}

write_cec_count() {
	echo -ne "\x$1" | dd of=/dev/kmem seek=$CEC_COUNT_OFFSET count=1 bs=1 2>/dev/null
}

write_cec_standby() {
	echo -ne "\x$1" | dd of=/dev/kmem seek=$CEC_STANDBY_OFFSET count=1 bs=1 2>/dev/null
}

read_cec_count() {
	dd if=/dev/kmem skip=$CEC_COUNT_OFFSET bs=1 count=1 2>/dev/null | hexdump -e '1/1 "%d"'
}


# Write the standby value and a count of 30
write_cec_standby $STANDBY_VALUE
write_cec_count 1e


echo -n Setting...


# Wait for the driver to decrement cec_count to 1
CEC_COUNT=30
while [ $CEC_COUNT -gt 1 ]; do

	CEC_COUNT=`read_cec_count`

	sleep 1
done

echo Done