SPI_WRITE_THEN_READ(9) Serial Peripheral Interface (S SPI_WRITE_THEN_READ(9)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 (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.
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 SPI_WRITE_THEN_READ(9)
Check Out this Related Man Page
SPI_ASYNC_LOCKED(9) Serial Peripheral Interface (S SPI_ASYNC_LOCKED(9)NAME
spi_async_locked - version of spi_async with exclusive bus usage
SYNOPSIS
int spi_async_locked(struct spi_device * spi, struct spi_message * message);
ARGUMENTS
spi
device with which data will be exchanged
message
describes the data transfers, including completion callback
CONTEXT
any (irqs may be blocked, etc)
DESCRIPTION
This call may be used in_irq and other contexts which can't sleep, as well as from task contexts which can sleep.
The completion callback is invoked in a context which can't sleep. Before that invocation, the value of message->status is undefined. When
the callback is issued, message->status holds either zero (to indicate complete success) or a negative error code. After that callback
returns, the driver which issued the transfer request may deallocate the associated memory; it's no longer in use by any SPI core or
controller driver code.
Note that although all messages to a spi_device are handled in FIFO order, messages may go to different devices in other orders. Some
device might be higher priority, or have various "hard" access time requirements, for example.
On detection of any fault during the transfer, processing of the entire message is aborted, and the device is deselected. Until returning
from the associated message completion callback, no other spi_message queued to that device will be processed. (This rule applies equally
to all the synchronous transfer calls, which are wrappers around this core asynchronous primitive.)
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 SPI_ASYNC_LOCKED(9)
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