fpi_usb_transfer_cb_fn ()

void
(*fpi_usb_transfer_cb_fn) (struct libusb_transfer *transfer,
                           struct fp_dev *dev,
                           fpi_ssm *ssm,
                           void *user_data);

This callback will be called in response to a libusb bulk transfer triggered via fpi_usb_fill_bulk_transfer() finishing. Note that the struct libusb_transfer does not need to be freed, as it will be freed after the callback returns, similarly to the LIBUSB_TRANSFER_FREE_TRANSFER flag.

Note that the cancelled status of the transfer should be checked first thing, as the dev , ssm and user_data pointers might not be pointing to valid values anymore. See fpi_usb_cancel_transfer() for more information.

fpi_usb_alloc ()

struct libusb_transfer *
fpi_usb_alloc (void);

Returns a struct libusb_transfer, similar to calling libusb_alloc_transfer(0)[1]. As libfprint uses GLib internally, and memory allocation failures will make applications fail, this helper will assert when the libusb call fails.

fpi_usb_fill_bulk_transfer ()

fpi_usb_transfer *
fpi_usb_fill_bulk_transfer (struct fp_dev *dev,
                            fpi_ssm *ssm,
                            unsigned char endpoint,
                            unsigned char *buffer,
                            int length,
                            fpi_usb_transfer_cb_fn callback,
                            void *user_data,
                            unsigned int timeout);

This function is similar to calling libusb_alloc_transfer(0)] followed by calling libusb_fill_bulk_transfer(). The fpi_usb_transfer_cb_fn callback will however provide more arguments relevant to libfprint drivers, making it a good replacement for the raw libusb calls.

fpi_usb_submit_transfer ()

int
fpi_usb_submit_transfer (fpi_usb_transfer *transfer);

Start a transfer to the device with the provided fpi_usb_transfer. On error, the fpi_usb_transfer struct will be freed, otherwise it will be freed once the callback provided to fpi_usb_fill_bulk_transfer() has been called.

fpi_usb_cancel_transfer ()

int
fpi_usb_cancel_transfer (fpi_usb_transfer *transfer);

Cancel a transfer to the device with the provided fpi_usb_transfer. Note that this will not complete the cancellation, as your transfer callback will be called with the LIBUSB_TRANSFER_CANCELLED status, as libusb_cancel_transfer would.

You should not access anything but the given struct libusb_transfer in the callback before checking whether LIBUSB_TRANSFER_CANCELLED has been called, as that might cause memory access violations.

fpi_usb_transfer

typedef struct fpi_usb_transfer fpi_usb_transfer;

A structure containing the arguments passed to fpi_usb_fill_bulk_transfer() to be used with fpi_usb_submit_transfer().