Linux Device Drivers Development

The device structure

The struct spi_device structure represents an SPI device, and is defined in include/linux/spi/spi.h:

struct spi_device { 
    struct devicedev; 
    struct spi_master*master; 
    u32 max_speed_hz; 
    u8 chip_select; 
    u8 bits_per_word; 
    u16 mode; 
    int irq; 
    [...] 
    int cs_gpio;        /* chip select gpio */ 
}; 

Some fields that are not meaningful for us have been removed.  The following are the meanings of the elements in the structure:

• master: This represents the SPI controller (bus) on which the device is connected.
• max_speed_hz: This is the maximum clock rate to be used with this chip (on the current board); this parameter can be changed from within the driver. You can override that parameter using spi_transfer.speed_hz for each transfer. We will ...