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 frame_length;
         unsigned actual_length;
         int status;
         struct list_head queue;
         void * state;
         struct list_head resources;
       };

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

       frame_length
           the total number of bytes in the message

       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

       resources
           for resource management when the spi message is processed

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 always 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 4.8.                 January 2017                     STRUCT SPI_MESSAGE(9)