Script for enabling mass storage emulation on rooted Samsung phones

serve_img.sh

A=/sys/class/android_usb/android0

set -x
killall -STOP adbd
sleep 1
echo 0 > $A/enable
echo mass_storage > $A/functions
echo disk > $A/f_mass_storage/luns
echo 1 > $A/enable
sleep 1
echo 0 > $A/enable
echo "$1" > $A/f_mass_storage/lun0/file
echo 1 > $A/enable

unserve_img.sh

A=/sys/class/android_usb/android0

set -x
echo 0 > $A/enable
echo mtp,acm,ffs > $A/functions
echo 1 > $A/enable
killall -CONT adbd