struct spi_driver — Host side “protocol” driver
struct spi_driver {
int (* probe) (struct spi_device *spi);
int (* remove) (struct spi_device *spi);
void (* shutdown) (struct spi_device *spi);
int (* suspend) (struct spi_device *spi, pm_message_t mesg);
int (* resume) (struct spi_device *spi);
struct device_driver driver;
}; Binds this driver to the spi device. Drivers can verify that the device is actually present, and may need to configure characteristics (such as bits_per_word) which weren't needed for the initial configuration done during system setup.
Unbinds this driver from the spi device
Standard shutdown callback used during system state transitions such as powerdown/halt and kexec
Standard suspend callback used during system state transitions
Standard resume callback used during system state transitions
SPI device drivers should initialize the name and owner field of this structure.
This represents the kind of device driver that uses SPI messages to interact with the hardware at the other end of a SPI link. It's called a “protocol” driver because it works through messages rather than talking directly to SPI hardware (which is what the underlying SPI controller driver does to pass those messages). These protocols are defined in the specification for the device(s) supported by the driver.
As a rule, those device protocols represent the lowest level interface supported by a driver, and it will support upper level interfaces too. Examples of such upper levels include frameworks like MTD, networking, MMC, RTC, filesystem character device nodes, and hardware monitoring.