1. NAME▲

struct_spi_master - interface to SPI master controller

2. SYNOPSIS ▲



 
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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;
};

3. 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 itAqs 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 itAqs 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 deviceAqs SPI controller; protocol code may call this. This must fail if an unrecognized or unsupported mode is requested. ItAqs always safe to call this unless transfers are pending on the device whose settings are being modified.

transfer
    adds a message to the controllerAqs 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).

4. 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 messageAqs completion function when the transaction completes.

5. COPYRIGHT ▲