libusb_transfer Struct Reference
[Asynchronous device I/O]

The generic USB transfer structure. More...

#include <libusb.h>

Data Fields
libusb_device_handle *	dev_handle
	Handle of the device that this transfer will be submitted to.
uint8_t	flags
	A bitwise OR combination of libusb_transfer_flags.
unsigned char	endpoint
	Address of the endpoint where this transfer will be sent.
unsigned char	type
	Type of the endpoint from libusb_transfer_type.
unsigned int	timeout
	Timeout for this transfer in millseconds.
enum libusb_transfer_status	status
	The status of the transfer.
int	length
	Length of the data buffer.
int	actual_length
	Actual length of data that was transferred.
libusb_transfer_cb_fn	callback
	Callback function.
void *	user_data
	User context data to pass to the callback function.
unsigned char *	buffer
	Data buffer.
int	num_iso_packets
	Number of isochronous packets.
struct libusb_iso_packet_descriptor	iso_packet_desc [0]
	Isochronous packet descriptors, for isochronous transfers only.

Detailed Description

The generic USB transfer structure.

The user populates this structure and then submits it in order to request a transfer. After the transfer has completed, the library populates the transfer with the results and passes it back to the user.

Field Documentation

uint8_t libusb_transfer::flags

A bitwise OR combination of libusb_transfer_flags.

unsigned char libusb_transfer::endpoint

Address of the endpoint where this transfer will be sent.

unsigned int libusb_transfer::timeout

Timeout for this transfer in millseconds.

A value of 0 indicates no timeout.

enum libusb_transfer_status libusb_transfer::status

The status of the transfer.

Read-only, and only for use within transfer callback function.

If this is an isochronous transfer, this field may read COMPLETED even if there were errors in the frames. Use the status field in each packet to determine if errors occurred.

int libusb_transfer::actual_length

Actual length of data that was transferred.

Read-only, and only for use within transfer callback function. Not valid for isochronous endpoint transfers.

libusb_transfer_cb_fn libusb_transfer::callback

Callback function.

This will be invoked when the transfer completes, fails, or is cancelled.

void* libusb_transfer::user_data

User context data to pass to the callback function.

int libusb_transfer::num_iso_packets

Number of isochronous packets.

Only used for I/O with isochronous endpoints.

struct libusb_iso_packet_descriptor libusb_transfer::iso_packet_desc[0]