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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;
       #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.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                      STRUCT SPI_MASTER(9)


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