F_RWOP
ret = regmap_field_write(i2c->fields[F_RWOP], xfer->write);
[F_RWOP] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL1, 2, 2),
[F_RWOP] = MST_REG_FIELD(RTL9310_I2C_MST_CTRL, 2, 2),