Section: Serial Peripheral Interface (S (9)
Updated: February 2011
Index Return to Main Contents


struct_spi_device - Master side proxy for an SPI slave device  


struct spi_device {
  struct device dev;
  struct spi_master * master;
  u32 max_speed_hz;
  u8 chip_select;
  u8 mode;
#define SPI_CPHA        0x01
#define SPI_CPOL        0x02
#define SPI_MODE_0      (0|0)
#define SPI_MODE_1      (0|SPI_CPHA)
#define SPI_MODE_2      (SPI_CPOL|0)
#define SPI_MODE_3      (SPI_CPOL|SPI_CPHA)
#define SPI_CS_HIGH     0x04
#define SPI_LSB_FIRST   0x08
#define SPI_3WIRE       0x10
#define SPI_LOOP        0x20
#define SPI_NO_CS       0x40
#define SPI_READY       0x80
  u8 bits_per_word;
  int irq;
  void * controller_state;
  void * controller_data;
  char modalias[SPI_NAME_SIZE];



Driver model representation of the device.


SPI controller used with the device.


Maximum clock rate to be used with this chip (on this board); may be changed by the device's driver. The spi_transfer.speed_hz can override this for each transfer.


Chipselect, distinguishing chips handled by master.


The spi mode defines how data is clocked out and in. This may be changed by the device's driver. The lqactive lowrq default for chipselect mode can be overridden (by specifying SPI_CS_HIGH) as can the lqMSB firstrq default for each word in a transfer (by specifying SPI_LSB_FIRST).


Data transfers involve one or more words; word sizes like eight or 12 bits are common. In-memory wordsizes are powers of two bytes (e.g. 20 bit samples use 32 bits). This may be changed by the device's driver, or left at the default (0) indicating protocol words are eight bit bytes. The spi_transfer.bits_per_word can override this for each transfer.


Negative, or the number passed to request_irq to receive interrupts from this device.


Controller's runtime state


Board-specific definitions for controller, such as FIFO initialization parameters; from board_info.controller_data


Name of the driver to use with this device, or an alias for that name. This appears in the sysfs lqmodaliasrq attribute for driver coldplugging, and in uevents used for hotplugging


A spi_device is used to interchange data between an SPI slave (usually a discrete chip) and CPU memory.

In dev, the platform_data is used to hold information about this device that's meaningful to the device's protocol driver, but not to its controller. One example might be an identifier for a chip variant with slightly different functionality; another might be information about how this particular board wires the chip's pins.