If secure-boot mode has been locked (via OTP) then both the
bootloader and rpiboot bootcode4.bin will only load boot.img
files signed with the customer's private key. Therefore, access
to rpiboot mass storage mode is disabled.
Mass storage mode can be re-enabled by signing a boot image containing the firmware mass storage drivers.
N.B. The signed image should normally be kept secure because can be used on any device signed with the same customer key.
To sign the mass storage mode boot image run:-
KEY_FILE=$HOME/private.pem
../tools/rpi-eeprom-digest -i boot.img -o boot.sig -k "${KEY_FILE}"To run load the USB MSD device drivers via RPIBOOT run
../rpiboot -d .