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Test Your Knowledge in Computers #567
Difficulty: Medium
The ternary if-then-else operator generally has the following syntax: E ? X : Y where E is a Boolean expression and if true, the statement is assigned the value Y.
True or False?
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struct_spi_message(9) [centos man page]

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)

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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)

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