void* underlay;
int (*read)(struct device* dev, void* buf, size_t offset, size_t len);
int (*write)(struct device* dev, void* buf, size_t offset, size_t len);
+ int (*read_page)(struct device* dev, void* buf, size_t offset);
+ int (*write_page)(struct device* dev, void* buf, size_t offset);
int (*exec_cmd)(struct device* dev, uint32_t req, va_list args);
};