spi_bus_lock(9) [centos man page]

SPI_BUS_LOCK(9) 					  Serial Peripheral Interface (S					   SPI_BUS_LOCK(9)

NAME

       spi_bus_lock - obtain a lock for exclusive SPI bus usage

SYNOPSIS

       int spi_bus_lock(struct spi_master * master);

ARGUMENTS

       master
	   SPI bus master that should be locked for exclusive bus access

CONTEXT

       can sleep

DESCRIPTION

       This call may only be used from a context that may sleep. The sleep is non-interruptible, and has no timeout.

       This call should be used by drivers that require exclusive access to the SPI bus. The SPI bus must be released by a spi_bus_unlock call
       when the exclusive access is over. Data transfer must be done by spi_sync_locked and spi_async_locked calls when the SPI bus lock is held.

       It returns zero on success, else a negative error code.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							   SPI_BUS_LOCK(9)

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.)

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							      SPI_ASYNC(9)