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)