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STRUCT 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

May 2024 Kernel Hackers Manual 2.6.