#!/bin/sh

. /etc/utils.sh

usage() {
  echo "Usage:"
  echo
  echo "  $0 {laser channel num}"
  echo
  echo "  Write to the I2C bus to tune the transceiver the specified channel"
  echo "  number."
  echo
  exit 99
}

if ! has-tuneable-laser; then
  # not all fiberjacks have tuneable optics.
  exit 0
fi

if [ "$#" -ne "1" ]; then
  usage
fi

# Make sure we've been given a decimal value.
if [ -z "${1##*[!0-9]*}" ]; then
  echo "Need a decimal laser channel value! Got: '$1' instead."
  exit 1
fi

# We are directly setting 4 bits of the lower byte (0x91).
# Make sure that it doesn't spill over into the upper byte 0x90.
# The PON-ID message format is here: http://go/golong-ponid-ploam-msg
# GFLT3 will only accept a channel inbetween 0-15
if [ "$1" -lt "0" ] && [ "$1" -gt "15" ]; then
  echo "Laser channel is out of range: $1 (range is: 0-15)"
  exit 1
fi

# Program the laser channel.
result=$(i2cset -y 0 0x51 0x90 0 $1 i)
if [ "$?" -ne "0" ]; then
  echo "Failed to set laser channel! i2cset error: $result"
  exit 1
fi

# Something funky is going on with the i2c bus after writing, sleeping for
# a while seems to allow us to consistently be able to read again.
sleep 1

result=$(i2cget -y 0 0x51 0x91)
if [ "$?" -ne "0" ]; then
  echo "Failed to get the laser channel! i2cget error: $result"
  exit 1
fi

# Some early transceiver firmware versions will only accept channel numbers 0
# through 13 (0xd). The final product uses "AWG absolute channel" numbers 0x05
# through 0x10 (channels 5 through 16).
if [ "$(($result))" -ne "$1" ]; then
  echo "Error verifying laser channel! Laser channel did not stick? " \
       "Expected: $1, got: $(($result))"
  exit 1
fi