1STRUCT SPI_MESSAGE(9)   Serial Peripheral Interface (S   STRUCT SPI_MESSAGE(9)
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NAME

6       struct_spi_message - one multi-segment SPI transaction
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SYNOPSIS

9       struct spi_message {
10         struct list_head transfers;
11         struct spi_device * spi;
12         unsigned is_dma_mapped:1;
13         void (* complete) (void *context);
14         void * context;
15         unsigned actual_length;
16         int status;
17         struct list_head queue;
18         void * state;
19       };
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MEMBERS

22       transfers
23           list of transfer segments in this transaction
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25       spi
26           SPI device to which the transaction is queued
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28       is_dma_mapped
29           if true, the caller provided both dma and cpu virtual addresses for
30           each transfer buffer
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32       complete
33           called to report transaction completions
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35       context
36           the argument to complete when it's called
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38       actual_length
39           the total number of bytes that were transferred in all successful
40           segments
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42       status
43           zero for success, else negative errno
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45       queue
46           for use by whichever driver currently owns the message
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48       state
49           for use by whichever driver currently owns the message
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DESCRIPTION

52       A spi_message is used to execute an atomic sequence of data transfers,
53       each represented by a struct spi_transfer. The sequence is “atomic” in
54       the sense that no other spi_message may use that SPI bus until that
55       sequence completes. On some systems, many such sequences can execute as
56       as single programmed DMA transfer. On all systems, these messages are
57       queued, and might complete after transactions to other devices.
58       Messages sent to a given spi_device are alway executed in FIFO order.
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60       The code that submits an spi_message (and its spi_transfers) to the
61       lower layers is responsible for managing its memory. Zero-initialize
62       every field you don't set up explicitly, to insulate against future API
63       updates. After you submit a message and its transfers, ignore them
64       until its completion callback.
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67Kernel Hackers Manual 3.10         June 2019             STRUCT SPI_MESSAGE(9)
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