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spi_async_locked(9) [centos man page]

SPI_ASYNC_LOCKED(9)					  Serial Peripheral Interface (S				       SPI_ASYNC_LOCKED(9)

spi_async_locked - version of spi_async with exclusive bus usage SYNOPSIS
int spi_async_locked(struct spi_device * spi, struct spi_message * message); ARGUMENTS
spi device with which data will be exchanged message describes the data transfers, including completion callback CONTEXT
any (irqs may be blocked, etc) DESCRIPTION
This call may be used in_irq and other contexts which can't sleep, as well as from task contexts which can sleep. The completion callback is invoked in a context which can't sleep. Before that invocation, the value of message->status is undefined. When the callback is issued, message->status holds either zero (to indicate complete success) or a negative error code. After that callback returns, the driver which issued the transfer request may deallocate the associated memory; it's no longer in use by any SPI core or controller driver code. Note that although all messages to a spi_device are handled in FIFO order, messages may go to different devices in other orders. Some device might be higher priority, or have various "hard" access time requirements, for example. On detection of any fault during the transfer, processing of the entire message is aborted, and the device is deselected. Until returning from the associated message completion callback, no other spi_message queued to that device will be processed. (This rule applies equally to all the synchronous transfer calls, which are wrappers around this core asynchronous primitive.) COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 SPI_ASYNC_LOCKED(9)

Check Out this Related Man Page

SPI_MASTER(9) Serial Peripheral Interface (S STRUCT SPI_MASTER(9) NAME
struct_spi_master - interface to SPI master controller SYNOPSIS
struct spi_master { struct device dev; s16 bus_num; u16 num_chipselect; u16 dma_alignment; u16 mode_bits; u16 flags; #define SPI_MASTER_HALF_DUPLEX BIT(0) #define SPI_MASTER_NO_RX BIT(1) #define SPI_MASTER_NO_TX BIT(2) int (* setup) (struct spi_device *spi); int (* transfer) (struct spi_device *spi,struct spi_message *mesg); void (* cleanup) (struct spi_device *spi); }; MEMBERS
dev device interface to this driver bus_num board-specific (and often SOC-specific) identifier for a given SPI controller. num_chipselect chipselects are used to distinguish individual SPI slaves, and are numbered from zero to num_chipselects. each slave has a chipselect signal, but it's common that not every chipselect is connected to a slave. dma_alignment SPI controller constraint on DMA buffers alignment. mode_bits flags understood by this controller driver flags other constraints relevant to this driver setup updates the device mode and clocking records used by a device's SPI controller; protocol code may call this. This must fail if an unrecognized or unsupported mode is requested. It's always safe to call this unless transfers are pending on the device whose settings are being modified. transfer adds a message to the controller's transfer queue. cleanup frees controller-specific state DESCRIPTION
Each SPI master controller can communicate with one or more spi_device children. These make a small bus, sharing MOSI, MISO and SCK signals but not chip select signals. Each device may be configured to use a different clock rate, since those shared signals are ignored unless the chip is selected. The driver for an SPI controller manages access to those devices through a queue of spi_message transactions, copying data between CPU memory and an SPI slave device. For each such message it queues, it calls the message's completion function when the transaction completes. COPYRIGHT
Kernel Hackers Manual 2.6. July 2010 STRUCT SPI_MASTER(9)

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