AD4851_REG_CHX_OFFSET_LSB
#define AD4851_REG_CHX_OFFSET_MID(ch) (AD4851_REG_CHX_OFFSET_LSB(ch) + 0x01)
ret = regmap_read(st->regmap, AD4851_REG_CHX_OFFSET_LSB(ch), &lsb);
ret = regmap_write(st->regmap, AD4851_REG_CHX_OFFSET_LSB(ch), buf[2]);