MPU9150 - compass calibration

Hi All,

I am integrating MPU9150 sensor with android ICS on a custom board.

I am able to load the sensor module & from the log message I am observing following messages:

V/Sensors ( 204): int open_sensors(const hw_module_t*, const char*, hw_device_t**)
V/Sensors ( 204): HAL:sysfs:cat /sys/bus/iio/devices/iio:device0/compass_matrix (23460235598)
I/Sensors ( 204): HAL: error : 50
E/Sensors ( 204): HAL:inv_start_mpl() failed
E/Sensors ( 204): HAL:Could not open or load MPL calibration file (46)
V/Sensors ( 204): HAL:sysfs:cat /sys/bus/iio/devices/iio:device0/in_magn_scale (23471588137)
V/Sensors ( 204): HAL:sysfs:echo 0 > /sys/bus/iio/devices/iio:device0/compass_enable (23554718020)
E/Sensors ( 204): HAL:ERR No DMP image
E/Sensors ( 204): HAL:ERR No DMP image
V/Sensors ( 204): int sensors_poll_context_t::activate(int, int)

From the above log message, I am able to infer that, it looks for a calibration file under /data/inv_cal_data.bin.. Is that mandatory? Because without the calibration file, in the Compass standard android app, I am not observing any variations.

Any sample calibration file or what is the input to generate the calibration file & how?
Any ideas?

Regards,
Ramya