SPI(9)

NAME
spi_configure, spi_transfer, spi_transfer_init, spi_chunk_init, spi_transfer_add, spi_wait, spi_done, spi_send, spi_recv, spi_send_recv - Serial Peripheral Interface (SPI) kernel interface

SYNOPSIS
#include <dev/spi/spivar.h>
int
spi_configure(struct spi_handle *sh, int mode, int speed);
int
spi_transfer(struct spi_handle *sh, struct spi_transfer *st);
void
spi_transfer_init(struct spi_transfer *st);
void
spi_chunk_init(struct spi_chunk *chunk, int cnt, const uint8_t *wptr, uint8_t *rptr);
void
spi_transfer_add(struct spi_transfer *st, struct spi_chunk *chunk);
void
spi_wait(struct spi_transfer *st);
void
spi_done(struct spi_transfer *st, int err);
int
spi_recv(struct spi_handle *sh, int cnt, uint8_t *data);
int
spi_send(struct spi_handle *sh, int cnt, const uint8_t *data);
int
spi_send_recv(struct spi_handle *sh, int scnt, const uint8_t *snd, int rcnt, const uint8_t *rcv);

DESCRIPTION
SPI is a 4-wire synchronous full-duplex serial bus. It is commonly used for connecting devices such as EEPROMs, displays, and other types of integrated circuits. The spi interface provides a means of communicating with SPI-connected devices.

FUNCTIONS
The following functions comprise the API provided to drivers of SPI-connected devices.

The struct spi_handle corresponding to the device is passed in the driver attachment.

spi_configure(sh, mode, speed)
    Sets mode and speed for subsequent communication with a SPI slave.

spi_transfer(sh, st)
    Queue transfer to SPI controller. spi_transfer() returns an errno value when the transfer couldn't be queued.

spi_transfer_init(st)
    Initialize a transfer structure.

spi_chunk_init(chunk, cnt, wptr, rptr")
    Initialize a chunk structure, each chunk corresponds to a possibly bi-directional transfer where the same amount of bytes is shifted in and out.

spi_transfer_add(st, chunk)
    Append a chunk to transfer structure.

spi_wait(st)
    Wait for a transfer to complete. When the transfer has failed for some reason, the field st->st_errno is set to a non-zero value.

spi_done(st, err)
    Called back machine-dependent backend to signal completion of a transfer.

For simplicity there are convenience functions that combine common operations. These functions return an errno value when the transfer failed.

spi_recv(sh, cnt, data)
    Prepares a chunk for receiving data, queues a transfer and waits for it to complete.

spi_send(sh, cnt, data)
    Prepares a chunk for sending data, queues a transfer and waits for it to complete.

spi_send_recv(sh, scnt, snd, rcnt, rcv)
    Prepares two chunks for sending data first and then receiving an answer, queues a transfer and waits for it to complete. This is not a full-duplex operation.

SEE ALSO
spi(4)

HISTORY
The spi API first appeared in NetBSD 4.0.