lp3972_i2c_read
lp3972_i2c_read(lp3972->i2c, reg, 1, &val);
ret = lp3972_i2c_read(lp3972->i2c, reg, 1, &tmp);
ret = lp3972_i2c_read(i2c, LP3972_SYS_CONTROL1_REG, 1, &val);