S49usbgadget

#!/bin/sh
# Setup Linux USB Gadget for adb, rndis
#   this is meant to be placed at /etc/init.d/S49usbgadget on the system_a partition of device

# Available options:

# usb_f_rndis.ko
# usb_f_fs.ko
# usb_f_midi.ko
# usb_f_mtp.ko
# usb_f_ptp.ko
# usb_f_audio_source.ko
# usb_f_accessory.ko


######### Variables

LANG="0x409"  # english
SERIAL_NUMBER="12345678"
# 18d1:4e40 Google Inc. Nexus 7
ID_VENDOR="0x18d1"
ID_PRODUCT="0x4e40"
MANUFACTURER="Spotify"
PRODUCT="Superbird"
ADBD_LOG_FILE="/tmp/adbd.log"


# Research
#   starting point: https://github.com/frederic/superbird-bulkcmd/blob/main/scripts/enable-adb.sh.client
#   info about configfs https://elinux.org/images/e/ef/USB_Gadget_Configfs_API_0.pdf
#   info about usbnet and bridging https://developer.ridgerun.com/wiki/index.php/How_to_use_USB_device_networking
#   more info, including for windows https://learn.adafruit.com/turning-your-raspberry-pi-zero-into-a-usb-gadget/ethernet-gadget
#   a gist that was helpful: https://gist.github.com/geekman/5bdb5abdc9ec6ac91d5646de0c0c60c4
#   https://www.kernel.org/doc/Documentation/usb/gadget_configfs.txt

######### Functions

create_device() {
    # create usb gadget device
    ID_VEND="$1"
    ID_PROD="$2"
    BCD_DEVICE="$3"
    BCD_USB="$4"
    LANGUAGE="$5"
    echo "###  Creating device $ID_VEND $ID_PROD"
    mkdir -p "/dev/usb-ffs"
    mkdir -p "/dev/usb-ffs/adb"
    mountpoint /sys/kernel/config/ || mount -t configfs none "/sys/kernel/config/"
    mkdir -p "/sys/kernel/config/usb_gadget/g1"
    echo "$ID_VEND" > "/sys/kernel/config/usb_gadget/g1/idVendor"
    echo "$ID_PROD" > "/sys/kernel/config/usb_gadget/g1/idProduct"
    echo "$BCD_DEVICE" > "/sys/kernel/config/usb_gadget/g1/bcdDevice"
    echo "$BCD_USB" > "/sys/kernel/config/usb_gadget/g1/bcdUSB"
    mkdir -p "/sys/kernel/config/usb_gadget/g1/strings/${LANGUAGE}"
    sleep 1
}

configure_device() {
    # configure usb gadget device
    MANUF="$1"
    PROD="$2"
    SERIAL="$3"
    LANGUAGE="$4"
    CONFIG_ID="$5"
    CONFIG_NAME="$6"
    echo "###  Configuring device as $MANUF $PROD"
    echo "$MANUF" > "/sys/kernel/config/usb_gadget/g1/strings/${LANGUAGE}/manufacturer"
    echo "$PROD" > "/sys/kernel/config/usb_gadget/g1/strings/${LANGUAGE}/product"
    echo "$SERIAL" > "/sys/kernel/config/usb_gadget/g1/strings/${LANGUAGE}/serialnumber"
    mkdir -p "/sys/kernel/config/usb_gadget/g1/configs/${CONFIG_ID}"
    mkdir -p "/sys/kernel/config/usb_gadget/g1/configs/${CONFIG_ID}/strings/${LANGUAGE}"
    echo "$CONFIG_NAME" > "/sys/kernel/config/usb_gadget/g1/configs/${CONFIG_ID}/strings/${LANGUAGE}/configuration"
    echo 500 > "/sys/kernel/config/usb_gadget/g1/configs/${CONFIG_ID}/MaxPower"
    ln -s "/sys/kernel/config/usb_gadget/g1/configs/${CONFIG_ID}" "/sys/kernel/config/usb_gadget/g1/os_desc/${CONFIG_ID}"
    sleep 1
}

add_function(){
    # add a function to existing config id
    FUNCTION_NAME="$1"
    CONFIG_ID="$2"
    echo "###  adding function $FUNCTION_NAME to config $CONFIG_ID"
    mkdir -p "/sys/kernel/config/usb_gadget/g1/functions/${FUNCTION_NAME}"
    ln -s "/sys/kernel/config/usb_gadget/g1/functions/${FUNCTION_NAME}" "/sys/kernel/config/usb_gadget/g1/configs/${CONFIG_ID}"
}

start_adb_daemon() {
    # mount adb functionfs and start daemon
    LOG_FILE="$1"
    echo "###  starting adb daemon"
    mkdir -p /dev/usb-ffs/adb
    mount -t functionfs adb /dev/usb-ffs/adb
    if [ ! -f "/usr/bin/adbd" ]; then
        echo "Unable to find adbd binary!"
    else
        /usr/bin/adbd > "$LOG_FILE" 2>&1 &
    fi
    sleep 5s
}

attach_driver(){
    # attach the created gadget device to our UDC driver
    UDC_DEVICE=$(/bin/ls -1 /sys/class/udc/)  # ff400000.dwc2_a
    echo "###  Attaching gadget to UDC device: $UDC_DEVICE"
    echo "$UDC_DEVICE" > /sys/kernel/config/usb_gadget/g1/UDC
    sleep 1
}

configure_usbnet() {
    DEVICE="$1"
    NETWORK="$2"  # just the first 3 octets
    NETMASK="$3"
    echo "###  bringing up $DEVICE with ${NETWORK}.2"
    ifconfig "$DEVICE" up
    ifconfig "$DEVICE" "${NETWORK}.2" netmask "$NETMASK" broadcast "${NETWORK}.255"
    echo "adding routes for $DEVICE"
    ip route add default via "${NETWORK}.1" dev "$DEVICE"
    sleep 1
}

######### Entrypoint

echo "### Configuring USB Gadget with adb and rndis"
create_device "$ID_VENDOR" "$ID_PRODUCT" "0x0223" "0x0200" "$LANG"
configure_device "$MANUFACTURER" "$PRODUCT" "$SERIAL_NUMBER" "$LANG" "b.1" "Multi-Function Device"

add_function "ffs.adb" "b.1"  # adb
add_function "rndis.usb0" "b.1"  # rndis usb ethernet

start_adb_daemon "$ADBD_LOG_FILE"

attach_driver

configure_usbnet "usb0" "192.168.7" "255.255.255.0"

echo "Done setting up USB Gadget"