SPI_WRITE_THEN_READ(9) Serial Peripheral Interface (S SPI_WRITE_THEN_READ(9)NAMEspi_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 (need not be dma-safe)
n_rx
size of rxbuf, in bytes
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.
COPYRIGHTKernel Hackers Manual 2.6. November 2013 SPI_WRITE_THEN_READ(9)