[PATCH v5 03/13] iio: core: add hierarchical channel relationships

[Rodrigo Alencar via B4 Relay]

From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>

Add parent-child relationship between iio channels by creating a parent
pointer field in iio_chan_spec struct and exposing a sysfs attribute that
returns the parent channel label.

Signed-off-by: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
---
 drivers/iio/industrialio-core.c | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/iio/iio.h         |  5 +++++
 2 files changed, 43 insertions(+)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 5c8404efd0a5..348ac7a59738 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -776,6 +776,14 @@ static ssize_t iio_read_channel_label(struct device *dev,
 					 to_iio_dev_attr(attr)->c, buf);
 }
 
+static ssize_t iio_read_channel_parent(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	return do_iio_read_channel_label(dev_to_iio_dev(dev),
+					 to_iio_dev_attr(attr)->c->parent, buf);
+}
+
 static ssize_t iio_read_channel_info(struct device *dev,
 				     struct device_attribute *attr,
 				     char *buf)
@@ -1263,6 +1271,31 @@ static int iio_device_add_channel_label(struct iio_dev *indio_dev,
 	return 1;
 }
 
+static int iio_device_add_channel_parent(struct iio_dev *indio_dev,
+					 struct iio_chan_spec const *chan)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	int ret;
+
+	if (!chan->parent || (!indio_dev->info->read_label &&
+			      !chan->parent->extend_name))
+		return 0;
+
+	ret = __iio_add_chan_devattr("parent",
+				     chan,
+				     &iio_read_channel_parent,
+				     NULL,
+				     0,
+				     IIO_SEPARATE,
+				     &indio_dev->dev,
+				     NULL,
+				     &iio_dev_opaque->channel_attr_list);
+	if (ret < 0)
+		return ret;
+
+	return 1;
+}
+
 static int iio_device_add_info_mask_type(struct iio_dev *indio_dev,
 					 struct iio_chan_spec const *chan,
 					 enum iio_shared_by shared_by,
@@ -1401,6 +1434,11 @@ static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
 		return ret;
 	attrcount += ret;
 
+	ret = iio_device_add_channel_parent(indio_dev, chan);
+	if (ret < 0)
+		return ret;
+	attrcount += ret;
+
 	if (chan->ext_info) {
 		unsigned int i = 0;
 
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 86d17ee69e05..09a97518e4bd 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -258,6 +258,10 @@ struct iio_scan_type {
  *			by all channels.
  * @info_mask_shared_by_all_available: What availability information is to be
  *			exported that is shared by all channels.
+ * @parent:		Optional pointer to the parent channel spec for
+ *			hierarchical channel relationships. When set, a read-only
+ *			"parent" sysfs attribute is created containing the
+ *			parent channel's label.
  * @event_spec:		Array of events which should be registered for this
  *			channel.
  * @num_event_specs:	Size of the event_spec array.
@@ -306,6 +310,7 @@ struct iio_chan_spec {
 	unsigned long			info_mask_shared_by_dir_available;
 	unsigned long			info_mask_shared_by_all;
 	unsigned long			info_mask_shared_by_all_available;
+	const struct iio_chan_spec *parent;
 	const struct iio_event_spec *event_spec;
 	unsigned int		num_event_specs;
 	const struct iio_chan_spec_ext_info *ext_info;

-- 
2.43.0