'\" t
.\"     Title: spi_async
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Serial Peripheral Interface (SPI)
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "SPI_ASYNC" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Serial Peripheral Interface (S"
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.SH "NAME"
spi_async \- asynchronous SPI transfer
.SH "SYNOPSIS"
.HP \w'int\ spi_async('u
.BI "int spi_async(struct\ spi_device\ *\ " "spi" ", struct\ spi_message\ *\ " "message" ");"
.SH "ARGUMENTS"
.PP
\fIspi\fR
.RS 4
device with which data will be exchanged
.RE
.PP
\fImessage\fR
.RS 4
describes the data transfers, including completion callback
.RE
.SH "CONTEXT"
.PP
any (irqs may be blocked, etc)
.SH "DESCRIPTION"
.PP
This call may be used in_irq and other contexts which can\*(Aqt sleep, as well as from task contexts which can sleep\&.
.PP
The completion callback is invoked in a context which can\*(Aqt 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\*(Aqs no longer in use by any SPI core or controller driver code\&.
.PP
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
\(lqhard\(rq
access time requirements, for example\&.
.PP
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\&.)
.SH "RETURN"
.PP
zero on success, else a negative error code\&.
.SH "COPYRIGHT"
.br