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

spi

is_dma_mapped

complete

context

actual_length

status

queue

state

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¶