I'm currently trying to make USB mass storage gadget work on a raspberry pi zero W.
My main objective is to implement both mass_storage and mtp responder functions into one gadget but it'll come later.
I followed this documentation Equivalent of g_mass_storage with configfs to write the following script which initializes the configuration for USB mass storage gadget through configfs and functionfs.
#!/bin/sh
set -e
CONFIGFS="/sys/kernel/config"
GADGET="$CONFIGFS/usb_gadget"
VID="0x0525"
PID="0xa4a2"
SERIAL="0123456789"
MANUF="Myself"
PRODUCT="MyProduct"
case "$1" in
start)
echo "Creating the USB gadget"
echo "Loading composite module"
modprobe libcomposite
echo "Creating gadget directory g1"
mkdir -p $GADGET/g1
cd $GADGET/g1
if [ $? -ne 0 ]; then
echo "Error creating usb gadget in configfs"
exit 1;
else
echo "OK"
fi
echo "Creating Mass Storage interface"
echo "\tCreating backing file"
dd if=/dev/zero of=/home/pi/backingFile.img bs=1024 count=1024 > /dev/null 2>&1
mkdosfs /home/pi/backingFile.img > /dev/null 2>&1
echo "\tOK"
echo "\tCreating gadget functionality"
mkdir functions/mass_storage.0
echo 1 > functions/mass_storage.0/stall
echo "/home/pi/backingFile.img" > functions/mass_storage.0/lun.0/file
echo 1 > functions/mass_storage.0/lun.0/removable
echo 0 > functions/mass_storage.0/lun.0/cdrom
mkdir configs/c.1
mkdir configs/c.1/strings/0x409
ln -s functions/mass_storage.0 configs/c.1
echo "\tOK"
echo "OK"
echo "Setting Vendor and Product ID's"
echo $VID > idVendor
echo $PID > idProduct
echo "OK"
echo "Setting English strings"
mkdir -p strings/0x409
echo $SERIAL > strings/0x409/serialnumber
echo $MANUF > strings/0x409/manufacturer
echo $PRODUCT > strings/0x409/product
echo "OK"
echo "Binding USB Device Controller"
echo `ls /sys/class/udc` > UDC
echo "OK"
;;
stop)
echo "Stopping the USB gadget"
cd $GADGET/g1
if [ $? -ne 0 ]; then
echo "Error: no configfs gadget found"
exit 1;
fi
echo "Unbinding USB Device Controller"
echo "" > UDC
echo "OK"
echo "Removing Mass Storage interface"
rm -f configs/c.1/mass_storage.0
rm -f /home/pi/backingFile.img
rmdir functions/mass_storage.0
echo "OK"
echo "Clearing English strings"
rmdir strings/0x409
echo "OK"
echo "Cleaning up configuration"
rmdir configs/c.1/strings/0x409
rmdir configs/c.1
echo "OK"
echo "Removing gadget directory"
cd $GADGET
rmdir g1
cd /
echo "OK"
echo "Disable composite USB gadgets"
modprobe -r libcomposite
echo "OK"
;;
*)
echo "Usage : $0 {start|stop}"
esac
Everything seems to work until the "Binding USB Device Controller" step. After having configured everything, there is still nothing in /sys/class/udc/
.
At boot, the folder /sys/class/udc/
doesn't exist and it appear after I run the script with sudo ./mass-storage-load start
but it stay empty.
The configfs partition is also mounted at boot.
After I ran the script, three new modules are loaded
pi@raspberrypi:~ $ lsmod
Module Size Used by
usb_f_mass_storage 44899 2
libcomposite 52156 10 usb_f_mass_storage
udc_core 40853 2 usb_f_mass_storage,libcomposite
However with nothing in /sys/class/udc
I don't know which usb device controller I should bind to this gadget.
I searched a lot on the internet to find someone that could have a similar issue but I'm not able to find something.
Best Answer
Finally the problem was that the module dwc2 had to be loaded.
So I added
dtoverlay=dwc2
to/boot/config.txt
anddwc2
at the end of/etc/modules
to load it automatically at boot.