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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;


  struct list_head list;


  s16 bus_num;


  u16 num_chipselect;


  u16 dma_alignment;


  u16 mode_bits;


  u32 bits_per_word_mask;


  u16 flags;
#define SPI_MASTER_HALF_DUPLEX	BIT(0)
#define SPI_MASTER_NO_RX	BIT(1)
#define SPI_MASTER_NO_TX	BIT(2)


  spinlock_t bus_lock_spinlock;


  struct mutex bus_lock_mutex;


  bool bus_lock_flag;


  int (* setup) (struct spi_device *spi);


  int (* transfer) (struct spi_device *spi,struct spi_message *mesg);


  void (* cleanup) (struct spi_device *spi);


  bool queued;


  struct kthread_worker kworker;


  struct task_struct * kworker_task;


  struct kthread_work pump_messages;


  spinlock_t queue_lock;


  struct list_head queue;


  struct spi_message * cur_msg;


  bool busy;


  bool running;


  bool rt;


  int (* prepare_transfer_hardware) (struct spi_master *master);


  int (* transfer_one_message) (struct spi_master *master,struct spi_message *mesg);


  int (* unprepare_transfer_hardware) (struct spi_master *master);


  int * cs_gpios;
};

MEMBERS

dev

device interface to this driver

list

link with the global spi_master list

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

bits_per_word_mask

A mask indicating which values of bits_per_word are supported by the driver. Bit n indicates that a bits_per_word n+1 is suported. If set, the SPI core will reject any transfer with an unsupported bits_per_word. If not set, this value is simply ignored, and it's up to the individual driver to perform any validation.

flags

other constraints relevant to this driver

bus_lock_spinlock

spinlock for SPI bus locking

bus_lock_mutex

mutex for SPI bus locking

bus_lock_flag

indicates that the SPI bus is locked for exclusive use

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

queued

whether this master is providing an internal message queue

kworker

thread struct for message pump

kworker_task

pointer to task for message pump kworker thread

pump_messages

work struct for scheduling work to the message pump

queue_lock

spinlock to syncronise access to message queue

queue

message queue

cur_msg

the currently in-flight message

busy

message pump is busy

running

message pump is running

rt

whether this queue is set to run as a realtime task

prepare_transfer_hardware

a message will soon arrive from the queue so the subsystem requests the driver to prepare the transfer hardware by issuing this call

transfer_one_message

the subsystem calls the driver to transfer a single message while queuing transfers that arrive in the meantime. When the driver is finished with this message, it must call spi_finalize_current_message so the subsystem can issue the next transfer

unprepare_transfer_hardware

there are currently no more messages on the queue so the subsystem notifies the driver that it may relax the hardware by issuing this call

cs_gpios

Array of GPIOs to use as chip select lines; one per CS number. Any individual value may be -ENOENT for CS lines that are not GPIOs (driven by the SPI controller itself).

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.

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June 2024 Kernel Hackers Manual 3.10