Name

spi_write_then_read — SPI synchronous write followed by read

Synopsis

int spi_write_then_read (struct spi_device *  spi,
 const u8 *  txbuf,
 unsigned  n_tx,
 u8 *  rxbuf,
 unsigned  n_rx);

Arguments

spi

device with which data will be exchanged

txbuf

data to be written (need not be dma-safe)

n_tx

size of txbuf, in bytes

rxbuf

buffer into which data will be read

n_rx

size of rxbuf, in bytes (need not be dma-safe)

Context

can sleep

Description

This performs a half duplex MicroWire style transaction with the device, sending txbuf and then reading rxbuf. The return value is zero for success, else a negative errno status code. This call may only be used from a context that may sleep.

Parameters to this routine are always copied using a small buffer; portable code should never use this for more than 32 bytes. Performance-sensitive or bulk transfer code should instead use spi_{async,sync}() calls with dma-safe buffers.