iio: backend: add support for data source get

Add backend support for getting the data source used.

The ad3552r HDL implements an internal ramp generator, so adding the
getter to allow data source get/set by debugfs.

Note: removed quotes for GPL export over porting to ADI linux.

Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Link: https://patch.msgid.link/20250409-wip-bl-ad3552r-fixes-v5-3-fb429c3a6515@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: spectrum70

drivers/iio/industrialio-backend.c

@@ -378,6 +378,34 @@ int iio_backend_data_source_set(struct iio_backend *back, unsigned int chan,
 }
 EXPORT_SYMBOL_NS_GPL(iio_backend_data_source_set, IIO_BACKEND);
 
+/**
+ * iio_backend_data_source_get - Get current data source
+ * @back: Backend device
+ * @chan: Channel number
+ * @data: Pointer to receive the current source value
+ *
+ * A given backend may have different sources to stream/sync data. This allows
+ * to know what source is in use.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int iio_backend_data_source_get(struct iio_backend *back, unsigned int chan,
+				enum iio_backend_data_source *data)
+{
+	int ret;
+
+	ret = iio_backend_op_call(back, data_source_get, chan, data);
+	if (ret)
+		return ret;
+
+	if (*data >= IIO_BACKEND_DATA_SOURCE_MAX)
+		return -EINVAL;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(iio_backend_data_source_get, IIO_BACKEND);
+
 /**
  * iio_backend_set_sampling_freq - Set channel sampling rate
  * @back: Backend device

include/linux/iio/backend.h

@@ -78,6 +78,7 @@ enum iio_backend_sample_trigger {
  * @chan_disable: Disable one channel.
  * @data_format_set: Configure the data format for a specific channel.
  * @data_source_set: Configure the data source for a specific channel.
+ * @data_source_get: Data source getter for a specific channel.
  * @set_sample_rate: Configure the sampling rate for a specific channel.
  * @test_pattern_set: Configure a test pattern.
  * @chan_status: Get the channel status.
@@ -106,6 +107,8 @@ struct iio_backend_ops {
 			       const struct iio_backend_data_fmt *data);
 	int (*data_source_set)(struct iio_backend *back, unsigned int chan,
 			       enum iio_backend_data_source data);
+	int (*data_source_get)(struct iio_backend *back, unsigned int chan,
+			       enum iio_backend_data_source *data);
 	int (*set_sample_rate)(struct iio_backend *back, unsigned int chan,
 			       u64 sample_rate_hz);
 	int (*test_pattern_set)(struct iio_backend *back,
@@ -162,6 +165,8 @@ int iio_backend_data_format_set(struct iio_backend *back, unsigned int chan,
 				const struct iio_backend_data_fmt *data);
 int iio_backend_data_source_set(struct iio_backend *back, unsigned int chan,
 				enum iio_backend_data_source data);
+int iio_backend_data_source_get(struct iio_backend *back, unsigned int chan,
+				enum iio_backend_data_source *data);
 int iio_backend_set_sampling_freq(struct iio_backend *back, unsigned int chan,
 				  u64 sample_rate_hz);
 int iio_backend_test_pattern_set(struct iio_backend *back,