iio: gyro: bmg160: add mount matrix support

This patch allows to read a mount-matrix device tree
property and report to user-space or in-kernel iio
clients.
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/gyro/bmg160_core.c

@@ -102,6 +102,7 @@ struct bmg160_data {
 	struct regmap *regmap;
 	struct iio_trigger *dready_trig;
 	struct iio_trigger *motion_trig;
+	struct iio_mount_matrix orientation;
 	struct mutex mutex;
 	s16 buffer[8];
 	u32 dps_range;
@@ -794,6 +795,20 @@ static int bmg160_write_event_config(struct iio_dev *indio_dev,
 	return 0;
 }
 
+static const struct iio_mount_matrix *
+bmg160_get_mount_matrix(const struct iio_dev *indio_dev,
+			 const struct iio_chan_spec *chan)
+{
+	struct bmg160_data *data = iio_priv(indio_dev);
+
+	return &data->orientation;
+}
+
+static const struct iio_chan_spec_ext_info bmg160_ext_info[] = {
+	IIO_MOUNT_MATRIX(IIO_SHARED_BY_DIR, bmg160_get_mount_matrix),
+	{ }
+};
+
 static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("100 200 400 1000 2000");
 
 static IIO_CONST_ATTR(in_anglvel_scale_available,
@@ -831,6 +846,7 @@ static const struct iio_event_spec bmg160_event = {
 		.storagebits = 16,					\
 		.endianness = IIO_LE,					\
 	},								\
+	.ext_info = bmg160_ext_info,					\
 	.event_spec = &bmg160_event,					\
 	.num_event_specs = 1						\
 }
@@ -1075,6 +1091,11 @@ int bmg160_core_probe(struct device *dev, struct regmap *regmap, int irq,
 	data->irq = irq;
 	data->regmap = regmap;
 
+	ret = iio_read_mount_matrix(dev, "mount-matrix",
+				&data->orientation);
+	if (ret)
+		return ret;
+
 	ret = bmg160_chip_init(data);
 	if (ret < 0)
 		return ret;