ad7091r_mode
enum ad7091r_mode mode;
int (*set_mode)(struct ad7091r_state *st, enum ad7091r_mode mode);
static int ad7091r5_set_mode(struct ad7091r_state *st, enum ad7091r_mode mode)
static int ad7091r8_set_mode(struct ad7091r_state *st, enum ad7091r_mode mode)