iio: magn: hmc5843: Fix buffer alignment in iio_push_to_buffers_with_timestamp()

To make code more readable, use a structure to express the channel
layout and ensure the timestamp is 8 byte aligned.

Found during an audit of all calls of uses of
iio_push_to_buffers_with_timestamp()

Fixes: 7247645f ("iio: hmc5843: Move hmc5843 out of staging")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210501170121.512209-16-jic23@kernel.org

drivers/iio/magnetometer/hmc5843.h

@@ -33,7 +33,8 @@ enum hmc5843_ids {
  * @lock:		update and read regmap data
  * @regmap:		hardware access register maps
  * @variant:		describe chip variants
- * @buffer:		3x 16-bit channels + padding + 64-bit timestamp
+ * @scan:		buffer to pack data for passing to
+ *			iio_push_to_buffers_with_timestamp()
  */
 struct hmc5843_data {
 	struct device *dev;
@@ -41,7 +42,10 @@ struct hmc5843_data {
 	struct regmap *regmap;
 	const struct hmc5843_chip_info *variant;
 	struct iio_mount_matrix orientation;
-	__be16 buffer[8];
+	struct {
+		__be16 chans[3];
+		s64 timestamp __aligned(8);
+	} scan;
 };
 
 int hmc5843_common_probe(struct device *dev, struct regmap *regmap,

drivers/iio/magnetometer/hmc5843_core.c

@@ -446,13 +446,13 @@ static irqreturn_t hmc5843_trigger_handler(int irq, void *p)
 	}
 
 	ret = regmap_bulk_read(data->regmap, HMC5843_DATA_OUT_MSB_REGS,
-			       data->buffer, 3 * sizeof(__be16));
+			       data->scan.chans, sizeof(data->scan.chans));
 
 	mutex_unlock(&data->lock);
 	if (ret < 0)
 		goto done;
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
 					   iio_get_time_ns(indio_dev));
 
 done: