The uMTP-Responder allows files to be transferred to and from devices through the devices USB port.

• Implemented in C.

• Lightweight implementation.

• User space implementation.

• As few dependencies as possible.

• Hook to the FunctionFS/libcomposite or the GadgetFS Linux layer.

• Dynamic handles allocation (No file-system pre-scan).

• Unicode support.

• (Optional) Syslog support.

• Folder listing.

• Folder creation.

• Files & Folders upload.

• Files & Folders download.

• Files & Folders deletion.

• Files & Folders renaming.

• Files / folders changes async events.

• Up to 16 storage instances supported.

• Storages mount / unmount.

• Storages lock / unlock.

• Global and Storages GID/UID override options.

• GadgetFS and FunctionFS/libcomposite modes supported.

Any board with a USB device port should be compatible. The only requirement is to have the USB FunctionFS (CONFIG_USB_FUNCTIONFS) or GadgetFS (CONFIG_USB_GADGETFS) support enabled in your Linux kernel. You also need to enable the board-specific USB device port driver (eg. dwc2 for the RaspberryPi Zero).

uMTP-Responder was tested on various Linux kernel versions (4.x.x / 5.x.x / 6.x.x ...) . This may work with earlier kernels (v3.x.x and some v2.6.x versions) but without any guarantee.

• Atmel Sama5D2 Xplained.

• Raspberry PI Zero (W).

• BeagleBone Black.

• Allwinner SoC based board.

• Freescale i.MX6 SabreSD. (Kernel v4.14)

• Samsung Artik710. (FunctionFS mode)

• Ultra96-V2 (Zynq UltraScale+, FunctionFS mode, SuperSpeed USB)

• Windows 7, Windows 10, Windows 11, Linux, Android.

The project is build using cmake. If you are compiling on the target, the compilation steps are:

mkdir build
cd build
cmake ..
make -j8

If you are using a cross-compile environment, you can use the CMAKE_TOOLCHAIN_FILE variable to specify your toolchain:

mkdir build
cd build
cmake -DCMAKE_TOOLCHAIN_FILE=<your_toolchain.cmake> ..
make -j8

A few compilation options are available:

• DEBUG_PRINT (default: OFF). Enable the debug ouput (on the console if syslog is not enabled)
• USE_SYSTEMD (default: ON). If systemd is available in the SDK, umtprd will notify systemd when it is ready.
• USE_SYSLOG (default: ON). Use syslog for the log messages
• OLD_FUNCTIONFS_DESCRIPTORS (default: OFF). Use it if you kernel version is < 3.15 (old-style FunctionFS descriptors support)
• SUPER_SPEED (default: OFF). Support for USB Super-Speed
• HIGH_SPEED (default: ON). Support for USB High-Speed
• FULL_SPEED (default: ON). Support for USB Full-Speed
• FILE_BUFFER_SZ (default: 1024). The size of the file read buffer in kB.
• USB_TX_BUFFER_SZ (default: 64). The size of the USB transmit buffer in kB.
• USB_RX_BUFFER_SZ (default: 64). The size of the USB receive buffer in kB.

A config file should copied into the folder /etc/umtprd/umtprd.conf This file defines the storage entries (host path and name), the MTP device name, the USB vendor & product IDs and the USB device configuration. Check the file umtprd.conf file for details on available options.

Once you have configured the correct settings in umtprd.conf, you can use umtprd_ffs.sh or umtprd_gfs.sh to launch it in FunctionFS/GadgetFS mode or use udev to launch the deamon when the usb device port is connected.

uMTP-Responder supports dynamic commands to add/mount/umount/remove storage and lock/unlock storage.

Examples:

Unlock all locked storage (set with the 'locked' option in the configuration file) :

umtprd -cmd:unlock

Lock all lockable storage (set with the 'locked' option in the configuration file) :

umtprd -cmd:lock

"addstorage"/"rmstorage" commands to dynamically add/remove storage :

umtprd '-cmd:addstorage:/tmp Tmp rw'

umtprd '-cmd:rmstorage:Tmp'

Use double-quotes when arguments have spaces in them:

umtprd '-cmd:addstorage:/path "My Path" rw,removable'

umtprd '-cmd:rmstorage:"My Path"'

"mount"/"unmount" commands to dynamically mount/unmount storage.

umtprd '-cmd:mount:"Storage name"'

umtprd '-cmd:unmount:"Storage name"'

This project is licensed under the GNU General Public License version 3 - see the LICENSE file for details