host/share/cros_write_firmware/spi.script

setenv _crc    'crc32 ${address} ${firmware_size}'
setenv _init   'echo Initing SPI;  sf probe            0'
setenv _erase  'echo Erasing SPI;  sf erase            0 ${length}'
setenv _write  'echo Writing SPI;  sf write ${address} 0 ${length}'
setenv _clear  'echo Clearing RAM; mw.b     ${address} 0 ${length}'
setenv _read   'echo Reading SPI;  sf read  ${address} 0 ${length}'

run _crc
run _init
run _erase
run _write
run _clear
run _read
run _crc

echo If the 2 CRCs above are equal, flash was successful