iio: core: Forbid use of both labels and extended names

Extended names are a problem for user-space as they make the filenames
in sysfs sometimes not parsable. They are now deprecated in favor of
labels.

This change makes sure that a device driver won't provide both labels
and extended names for its channels. It has never been the case and we
don't want it to happen.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210618123005.49867-2-paul@crapouillou.netSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -1858,6 +1858,24 @@ static int iio_check_unique_scan_index(struct iio_dev *indio_dev)
 	return 0;
 }
 
+static int iio_check_extended_name(const struct iio_dev *indio_dev)
+{
+	unsigned int i;
+
+	if (!indio_dev->info->read_label)
+		return 0;
+
+	for (i = 0; i < indio_dev->num_channels; i++) {
+		if (indio_dev->channels[i].extend_name) {
+			dev_err(&indio_dev->dev,
+				"Cannot use labels and extend_name at the same time\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 static const struct iio_buffer_setup_ops noop_ring_setup_ops;
 
 int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
@@ -1882,6 +1900,10 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
 	if (ret < 0)
 		return ret;
 
+	ret = iio_check_extended_name(indio_dev);
+	if (ret < 0)
+		return ret;
+
 	iio_device_register_debugfs(indio_dev);
 
 	ret = iio_buffers_alloc_sysfs_and_mask(indio_dev);