struct_spi_message(9) [centos man page]

STRUCT 
SPI_MESSAGE(9)					  Serial Peripheral Interface (S				     STRUCT SPI_MESSAGE(9)

NAME

       struct_spi_message - one multi-segment SPI transaction

SYNOPSIS

       struct spi_message {
	 struct list_head transfers;
	 struct spi_device * spi;
	 unsigned is_dma_mapped:1;
	 void (* complete) (void *context);
	 void * context;
	 unsigned actual_length;
	 int status;
	 struct list_head queue;
	 void * state;
       };

MEMBERS

       transfers
	   list of transfer segments in this transaction

       spi
	   SPI device to which the transaction is queued

       is_dma_mapped
	   if true, the caller provided both dma and cpu virtual addresses for each transfer buffer

       complete
	   called to report transaction completions

       context
	   the argument to complete when it's called

       actual_length
	   the total number of bytes that were transferred in all successful segments

       status
	   zero for success, else negative errno

       queue
	   for use by whichever driver currently owns the message

       state
	   for use by whichever driver currently owns the message

DESCRIPTION

       A spi_message is used to execute an atomic sequence of data transfers, each represented by a struct spi_transfer. The sequence is "atomic"
       in the sense that no other spi_message may use that SPI bus until that sequence completes. On some systems, many such sequences can execute
       as as single programmed DMA transfer. On all systems, these messages are queued, and might complete after transactions to other devices.
       Messages sent to a given spi_device are alway executed in FIFO order.

       The code that submits an spi_message (and its spi_transfers) to the lower layers is responsible for managing its memory. Zero-initialize
       every field you don't set up explicitly, to insulate against future API updates. After you submit a message and its transfers, ignore them
       until its completion callback.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014						     STRUCT SPI_MESSAGE(9)

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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)

Linux and UNIX Man Pages

struct_spi_message(9) [centos man page]

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