MTP¶

Role: device only. Media Transfer Protocol (MTP) presents objects and object metadata rather than a host-mounted block device. It is a better fit than MSC when device firmware and the host must access managed files concurrently.

Configuration¶

Set CFG_TUD_MTP to 1 and add TUD_MTP_DESCRIPTOR. Configure the endpoint and control buffers, then advertise only operations, events, properties, and formats that the application actually implements:

#define CFG_TUD_MTP                    1
#define CFG_TUD_MTP_EP_BUFSIZE         512
#define CFG_TUD_MTP_EP_CONTROL_BUFSIZE 16

#define CFG_TUD_MTP_DEVICEINFO_EXTENSIONS "microsoft.com: 1.0; "
#define CFG_TUD_MTP_DEVICEINFO_SUPPORTED_OPERATIONS \
  MTP_OP_GET_DEVICE_INFO, MTP_OP_OPEN_SESSION, MTP_OP_CLOSE_SESSION
#define CFG_TUD_MTP_DEVICEINFO_SUPPORTED_EVENTS \
  MTP_EVENT_OBJECT_ADDED
#define CFG_TUD_MTP_DEVICEINFO_SUPPORTED_DEVICE_PROPERTIES \
  MTP_DEV_PROP_DEVICE_FRIENDLY_NAME
#define CFG_TUD_MTP_DEVICEINFO_CAPTURE_FORMATS \
  MTP_OBJ_FORMAT_UNDEFINED, MTP_OBJ_FORMAT_ASSOCIATION
#define CFG_TUD_MTP_DEVICEINFO_PLAYBACK_FORMATS \
  MTP_OBJ_FORMAT_UNDEFINED, MTP_OBJ_FORMAT_ASSOCIATION

Option	Default	What it controls
`CFG_TUD_MTP_EP_BUFSIZE`	Required	Shared bulk data buffer and maximum data chunk, at most 65535 bytes. Larger values improve throughput but consume static RAM.
`CFG_TUD_MTP_EP_CONTROL_BUFSIZE`	Required	Staging buffer for MTP class control requests and responses.
`CFG_TUD_MTP_DEVICEINFO_EXTENSIONS`	Required	MTP extension string returned by GetDeviceInfo; use an empty string when no extension is implemented.
`CFG_TUD_MTP_DEVICEINFO_SUPPORTED_OPERATIONS`	Required	Operation codes the host is told it may issue.
`CFG_TUD_MTP_DEVICEINFO_SUPPORTED_EVENTS`	Required	Event codes the device may send on the interrupt endpoint.
`CFG_TUD_MTP_DEVICEINFO_SUPPORTED_DEVICE_PROPERTIES`	Required	Device property codes supported by the application.
`CFG_TUD_MTP_DEVICEINFO_CAPTURE_FORMATS` / `CFG_TUD_MTP_DEVICEINFO_PLAYBACK_FORMATS`	Required	Object formats the device can create or expose for playback.

The CFG_TUD_MTP_DEVICEINFO_* lists form the GetDeviceInfo response and are a contract with the host.

Application flow¶

API or callback	What it does
`tud_mtp_mounted()`	Tests whether the bulk OUT and bulk IN endpoints are open.
`tud_mtp_command_received_cb()`	Delivers the operation container and starts the application transaction state machine. A negative return stalls both bulk endpoints.
`tud_mtp_data_send()` / `tud_mtp_data_receive()`	Starts or continues the operation’s data phase. Returns `false` without changing phase if the transfer cannot be queued.
`tud_mtp_response_send()`	Queues the final response container with the current transaction ID. Returns `false` without changing phase if the response cannot be queued. May also be called from `tud_mtp_data_xfer_cb()` before the data-complete notification; the driver absorbs a pending terminating OUT ZLP. Responding before all OUT payload arrives stalls both bulk endpoints and discards the queued response.
`tud_mtp_event_send()`	Copies and queues one asynchronous event. Send the next event only after the previous one has gone out: a call while the event endpoint is busy overwrites the event still in flight before returning `false`.
`tud_mtp_data_xfer_cb()`	Supplies or consumes the next chunk of a multi-packet data phase. A negative return stalls both bulk endpoints.
`tud_mtp_data_complete_cb()`	Advances application state after the entire data phase. A negative return stalls both bulk endpoints.
`tud_mtp_response_complete_cb()`	Advances application state after the response phase.
`tud_mtp_request_*_cb()`	Handles cancel, reset, status, extended-event, and vendor control requests. Return `false` or a negative length where documented to stall an unsupported request. The driver handles transport recovery for Cancel and Device Reset; their callbacks update application state. In the error phase, the driver answers Get Device Status without calling the application.

tud_mtp_command_received_cb() receives an operation container. The application performs any data phase with tud_mtp_data_send() or tud_mtp_data_receive(), then completes the transaction with tud_mtp_response_send(). Use tud_mtp_event_send() for asynchronous events such as ObjectAdded.

The tud_mtp_data_xfer_cb(), tud_mtp_data_complete_cb(), and tud_mtp_response_complete_cb() callbacks advance multi-stage transfers. Validate container lengths, object handles, property codes, and storage bounds before using them.

The MTP example is the recommended template. It implements a small in-memory object store, core session/object operations, and an upload. Replace its storage functions while preserving the command/data/response state machine.

TinyUSB supplies the USB transport and MTP containers; it does not provide a filesystem, object database, stable handle allocation, or access arbitration. Those remain application responsibilities.