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, u32_t req, va_list args);
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, u32_t req, va_list args);