spi_sync(9) [suse man page]

SPI_SYNC(9)						  Serial Peripheral Interface (S					       SPI_SYNC(9)

NAME

       spi_sync - blocking/synchronous SPI data transfers

SYNOPSIS

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

ARGUMENTS

       spi
	   device with which data will be exchanged

       message
	   describes the data transfers

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. Low-overhead controller
       drivers may DMA directly into and out of the message buffers.

       Note that the SPI device's chip select is active during the message, and then is normally disabled between messages. Drivers for some
       frequently-used devices may want to minimize costs of selecting a chip, by leaving it selected in anticipation that the next message will
       go to the same chip. (That may increase power usage.)

       Also, the caller is guaranteeing that the memory associated with the message will not be freed before this call returns.

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

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010							       SPI_SYNC(9)

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 2.6.					     July 2010						     STRUCT SPI_MESSAGE(9)