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;
#define SPI_BPW_MASK(bits) BIT((bits) - 1)
#define SPI_BIT_MASK(bits) (((bits) == 32) ? ~0U : (BIT(bits) - 1))
#define SPI_BPW_RANGE_MASK(min# max) (SPI_BIT_MASK(max) - SPI_BIT_MASK(min - 1))
  u32 min_speed_hz;
  u32 max_speed_hz;
  u16 flags;
#define SPI_MASTER_HALF_DUPLEX	BIT(0)
#define SPI_MASTER_NO_RX	BIT(1)
#define SPI_MASTER_NO_TX	BIT(2)
#define SPI_MASTER_MUST_RX      BIT(3)
#define SPI_MASTER_MUST_TX      BIT(4)
  size_t (* max_transfer_size) (struct spi_device *spi);
  struct mutex io_mutex;
  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 (* can_dma) (struct spi_master *master,struct spi_device *spi,struct spi_transfer *xfer);
  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 idling;
  bool busy;
  bool running;
  bool rt;
  bool auto_runtime_pm;
  bool cur_msg_prepared;
  bool cur_msg_mapped;
  struct completion xfer_completion;
  size_t max_dma_len;
  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 (* prepare_message) (struct spi_master *master,struct spi_message *message);
  int (* unprepare_message) (struct spi_master *master,struct spi_message *message);
  int (* spi_flash_read) (struct  spi_device *spi,struct spi_flash_read_message *msg);
  bool (* flash_read_supported) (struct spi_device *spi);
  void (* set_cs) (struct spi_device *spi, bool enable);
  int (* transfer_one) (struct spi_master *master, struct spi_device *spi,struct spi_transfer *transfer);
  void (* handle_err) (struct spi_master *master,struct spi_message *message);
  int * cs_gpios;
  struct spi_statistics statistics;
  struct dma_chan * dma_tx;
  struct dma_chan * dma_rx;
  void * dummy_rx;
  void * dummy_tx;
  int (* fw_translate_cs) (struct spi_master *master, unsigned cs);
};  

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 supported. 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.

min_speed_hz

Lowest supported transfer speed

max_speed_hz

Highest supported transfer speed

flags

other constraints relevant to this driver

max_transfer_size

function that returns the max transfer size for a spi_device; may be NULL, so the default SIZE_MAX will be used.

io_mutex

mutex for physical bus access

bus_lock_spinlock

spinlock for SPI bus locking

bus_lock_mutex

mutex for exclusion of multiple callers

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

can_dma

determine whether this master supports DMA

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

idling

the device is entering idle state

busy

message pump is busy

running

message pump is running

rt

whether this queue is set to run as a realtime task

auto_runtime_pm

the core should ensure a runtime PM reference is held while the hardware is prepared, using the parent device for the spidev

cur_msg_prepared

spi_prepare_message was called for the currently in-flight message

cur_msg_mapped

message has been mapped for DMA

xfer_completion

used by core transfer_one_message

max_dma_len

Maximum length of a DMA transfer for the device.

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 message

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

prepare_message

set up the controller to transfer a single message, for example doing DMA mapping. Called from threaded context.

unprepare_message

undo any work done by prepare_message.

spi_flash_read

to support spi-controller hardwares that provide accelerated interface to read from flash devices.

flash_read_supported

spi device supports flash read

set_cs

set the logic level of the chip select line. May be called from interrupt context.

transfer_one

transfer a single spi_transfer. - return 0 if the transfer is finished, - return 1 if the transfer is still in progress. When the driver is finished with this transfer it must call spi_finalize_current_transfer so the subsystem can issue the next transfer. Note: transfer_one and transfer_one_message are mutually exclusive; when both are set, the generic subsystem does not call your transfer_one callback.

handle_err

the subsystem calls the driver to handle an error that occurs in the generic implementation of transfer_one_message.

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).

statistics

statistics for the spi_master

dma_tx

DMA transmit channel

dma_rx

DMA receive channel

dummy_rx

dummy receive buffer for full-duplex devices

dummy_tx

dummy transmit buffer for full-duplex devices

fw_translate_cs

If the boot firmware uses different numbering scheme what Linux expects, this optional hook can be used to translate between the two.

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.