root/include/linux/spi/mcp23s08.h

/* FIXME driver should be able to handle IRQs...  */

struct mcp23s08_chip_info {
        bool    is_present;             /* true iff populated */
        u8      pullups;                /* BIT(x) means enable pullup x */
};

struct mcp23s08_platform_data {
        /* Four slaves (numbered 0..3) can share one SPI chipselect, and
         * will provide 8..32 GPIOs using 1..4 gpio_chip instances.
         */
        struct mcp23s08_chip_info       chip[4];

        /* "base" is the number of the first GPIO.  Dynamic assignment is
         * not currently supported, and even if there are gaps in chip
         * addressing the GPIO numbers are sequential .. so for example
         * if only slaves 0 and 3 are present, their GPIOs range from
         * base to base+15.
         */
        unsigned        base;

        void            *context;       /* param to setup/teardown */

        int             (*setup)(struct spi_device *spi,
                                        int gpio, unsigned ngpio,
                                        void *context);
        int             (*teardown)(struct spi_device *spi,
                                        int gpio, unsigned ngpio,
                                        void *context);
};