[PATCH 3/8] iio: add child nodes support in iio backend framework

[Olivier Moysan <olivier.moysan@foss.st.com>]

Add an API to support IIO generic channels binding:
http://devicetree.org/schemas/iio/adc/adc.yaml#
This new API is needed, as generic channel DT node
isn't populated as a device.
Add devm_iio_backend_subnode_get() to allow an IIO device
backend consumer to configure backend phandles in its
child nodes.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 drivers/iio/industrialio-backend.c | 48 ++++++++++++++++++++++--------
 include/linux/iio/backend.h        |  2 ++
 2 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index d3db048c086b..e9d29131634d 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -575,17 +575,8 @@ static int __devm_iio_backend_get(struct device *dev, struct iio_backend *back)
 	return 0;
 }
 
-/**
- * devm_iio_backend_get - Device managed backend device get
- * @dev: Consumer device for the backend
- * @name: Backend name
- *
- * Get's the backend associated with @dev.
- *
- * RETURNS:
- * A backend pointer, negative error pointer otherwise.
- */
-struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
+static struct iio_backend *__devm_iio_backend_node_get(struct device *dev, const char *name,
+						       struct fwnode_handle *node)
 {
 	struct fwnode_handle *fwnode;
 	struct iio_backend *back;
@@ -602,7 +593,7 @@ struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
 		index = 0;
 	}
 
-	fwnode = fwnode_find_reference(dev_fwnode(dev), "io-backends", index);
+	fwnode = fwnode_find_reference(node, "io-backends", index);
 	if (IS_ERR(fwnode)) {
 		dev_err_probe(dev, PTR_ERR(fwnode),
 			      "Cannot get Firmware reference\n");
@@ -625,8 +616,41 @@ struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
 	fwnode_handle_put(fwnode);
 	return ERR_PTR(-EPROBE_DEFER);
 }
+
+/**
+ * devm_iio_backend_get - Device managed backend device get
+ * @dev: Consumer device for the backend
+ * @name: Backend name
+ *
+ * Get's the backend associated with @dev.
+ *
+ * RETURNS:
+ * A backend pointer, negative error pointer otherwise.
+ */
+struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
+{
+	return __devm_iio_backend_node_get(dev, name, dev_fwnode(dev));
+}
 EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get, IIO_BACKEND);
 
+/**
+ * devm_iio_backend_subnode_get - Device managed backend device get
+ * @dev: Consumer device for the backend
+ * @name: Backend name
+ * @node: Firmware node of the backend consumer
+ *
+ * Get's the backend associated with @dev.
+ *
+ * RETURNS:
+ * A backend pointer, negative error pointer otherwise.
+ */
+struct iio_backend *devm_iio_backend_subnode_get(struct device *dev, const char *name,
+						 struct fwnode_handle *node)
+{
+	return __devm_iio_backend_node_get(dev, name, node);
+}
+EXPORT_SYMBOL_NS_GPL(devm_iio_backend_subnode_get, IIO_BACKEND);
+
 /**
  * __devm_iio_backend_get_from_fwnode_lookup - Device managed fwnode backend device get
  * @dev: Consumer device for the backend
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index 81277e5b6160..1050ab68e4e4 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -152,6 +152,8 @@ int iio_backend_extend_chan_spec(struct iio_dev *indio_dev,
 				 struct iio_chan_spec *chan);
 void *iio_backend_get_priv(const struct iio_backend *conv);
 struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name);
+struct iio_backend *devm_iio_backend_subnode_get(struct device *dev, const char *name,
+						 struct fwnode_handle *node);
 struct iio_backend *
 __devm_iio_backend_get_from_fwnode_lookup(struct device *dev,
 					  struct fwnode_handle *fwnode);
-- 
2.25.1