SPI transfer helpers: libfprint Reference Manual

SPI transfer helpers

SPI transfer helpers — Helpers to ease SPI transfers

Functions

void	(*FpiSpiTransferCallback) ()
FpiSpiTransfer *	fpi_spi_transfer_new ()
FpiSpiTransfer *	fpi_spi_transfer_ref ()
void	fpi_spi_transfer_unref ()
void	fpi_spi_transfer_write ()
void	fpi_spi_transfer_write_full ()
void	fpi_spi_transfer_read ()
void	fpi_spi_transfer_read_full ()
void	fpi_spi_transfer_submit ()
gboolean	fpi_spi_transfer_submit_sync ()

Types and Values

FpiSpiTransfer

Description

FpiSpiTransfer is a structure to simplify the SPI transfer handling for the linux spidev device. The main goal are to ease memory management and provide a usable asynchronous API to libfprint drivers.

Currently only transfers with a write and subsequent read are supported.

Drivers should always use this API rather than calling read/write/ioctl on the spidev device.

Setting G_MESSAGES_DEBUG and FP_DEBUG_TRANSFER will result in the message content to be dumped.

Functions

FpiSpiTransferCallback ()

void
(*FpiSpiTransferCallback) (FpiSpiTransfer *transfer,
                           FpDevice *dev,
                           gpointer user_data,
                           GError *error);

fpi_spi_transfer_new ()

FpiSpiTransfer *
fpi_spi_transfer_new (FpDevice *device,
                      int spidev_fd);

Creates a new FpiSpiTransfer.

Parameters

device	The FpDevice the transfer is for
spidev_fd	The file descriptor for the spidev device

Returns

A newly created FpiSpiTransfer.

[transfer full]

fpi_spi_transfer_ref ()

FpiSpiTransfer *
fpi_spi_transfer_ref (FpiSpiTransfer *self);

Increments the reference count of self by one.

Parameters

self

A FpiSpiTransfer

Returns

self .

[transfer full]

fpi_spi_transfer_unref ()

void
fpi_spi_transfer_unref (FpiSpiTransfer *self);

Decrements the reference count of self by one, freeing the structure when the reference count reaches zero.

Parameters

self

A FpiSpiTransfer

fpi_spi_transfer_write ()

void
fpi_spi_transfer_write (FpiSpiTransfer *transfer,
                        gsize length);

Prepare the write part of an SPI transfer allocating a new buffer internally that will be free'ed automatically.

Parameters

transfer	The FpiSpiTransfer
length	The buffer size to allocate

fpi_spi_transfer_write_full ()

void
fpi_spi_transfer_write_full (FpiSpiTransfer *transfer,
                             guint8 *buffer,
                             gsize length,
                             GDestroyNotify free_func);

Prepare the write part of an SPI transfer.

Parameters

transfer	The FpiSpiTransfer
buffer	The data to write.
length	The size of `buffer`
free_func	Destroy notify for `buffer` .	[destroy buffer]

fpi_spi_transfer_read ()

void
fpi_spi_transfer_read (FpiSpiTransfer *transfer,
                       gsize length);

Prepare the read part of an SPI transfer allocating a new buffer internally that will be free'ed automatically.

Parameters

transfer	The FpiSpiTransfer
length	The buffer size to allocate

fpi_spi_transfer_read_full ()

void
fpi_spi_transfer_read_full (FpiSpiTransfer *transfer,
                            guint8 *buffer,
                            gsize length,
                            GDestroyNotify free_func);

Prepare the read part of an SPI transfer.

Parameters

transfer	The FpiSpiTransfer
buffer	Buffer to read data into.
length	The size of `buffer`
free_func	Destroy notify for `buffer` .	[destroy buffer]

fpi_spi_transfer_submit ()

void
fpi_spi_transfer_submit (FpiSpiTransfer *transfer,
                         GCancellable *cancellable,
                         FpiSpiTransferCallback callback,
                         gpointer user_data);

Submit an SPI transfer with a specific timeout and callback functions.

The underlying transfer cannot be cancelled. The current implementation will only call callback after the transfer has been completed.

Note that FpiSpiTransfer will be stolen when this function is called. So that all associated data will be free'ed automatically, after the callback ran unless fpi_usb_transfer_ref() is explicitly called.

Parameters

transfer	The transfer to submit, must have been filled.	[transfer full]
cancellable	Cancellable to use, e.g. `fpi_device_get_cancellable()`
callback	Callback on completion or error
user_data	Data to pass to callback

fpi_spi_transfer_submit_sync ()

gboolean
fpi_spi_transfer_submit_sync (FpiSpiTransfer *transfer,
                              GError **error);

Synchronously submit an SPI transfer. Use of this function is discouraged as it will block all other operations in the application.

Note that you still need to fpi_spi_transfer_unref() the FpiSpiTransfer afterwards.

Parameters

transfer	The transfer to submit, must have been filled.
error	Location to store GError to

Returns

TRUE on success, otherwise FALSE and error will be set

Types and Values

FpiSpiTransfer

typedef struct {
  FpDevice *device;

  FpiSsm   *ssm;

  gssize    length_wr;
  gssize    length_rd;

  guchar   *buffer_wr;
  guchar   *buffer_rd;
} FpiSpiTransfer;

Helper for handling SPI transfers. Currently transfers can either be pure write/read transfers or a write followed by a read (full duplex support can easily be added if desired).

Members

FpDevice *`device`;	The FpDevice that the transfer belongs to.
FpiSsm *`ssm`;	Storage slot to associate the transfer with a state machine. Used by `fpi_ssm_spi_transfer_cb()` to modify the given state machine.
gssize `length_wr`;	The length of the write buffer
gssize `length_rd`;	The length of the read buffer
guchar *`buffer_wr`;	The write buffer.
guchar *`buffer_rd`;	The read buffer.