F_DATA_WIDTH
ret = regmap_field_write(i2c->fields[F_DATA_WIDTH], (xfer->data_len - 1) & 0xf);
[F_DATA_WIDTH] = MST_REG_FIELD(RTL9300_I2C_MST_CTRL2, 4, 7),
[F_DATA_WIDTH] = MST_REG_FIELD(RTL9310_I2C_MST_CTRL, 5, 8),
[F_DATA_WIDTH] = MST_REG_FIELD(RTL9607_I2C_CONFIG, 10, 11),