SPI_ASYNC(9) Serial Peripheral Interface (S SPI_ASYNC(9)NAME
spi_async - asynchronous SPI transfer
SYNOPSIS
int spi_async(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.)
COPYRIGHTKernel Hackers Manual 2.6. November 2013 SPI_ASYNC(9)
