Man page 9 : spi_async

spi_async - asynchronous SPI transfer

int spi_async(struct spi_device *  spi , struct spi_message *  message );

spi
    device with which data will be exchanged

message
    describes the data transfers, including completion callback

any (irqs may be blocked, etc)

This call may be used in_irq and other contexts which canAqt sleep, as well as from task contexts which can sleep.

The completion callback is invoked in a context which canAqt 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; itAqs 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.)