[PATCH net-next v5 3/7] i2c: mux: Propagate software nodes to channel adapters

[Ahmad Byagowi]

Device Tree channel nodes are associated with the adapters created by
i2c-mux, but equivalent software-node descriptions are not.

Find the software-node child whose reg value matches the channel and
attach it to the new adapter. Preserve an ACPI primary node when present
and extend I2C firmware-node adapter lookup to match the attached
secondary node.

Track attachment ownership so failure cleanup cannot detach a
pre-existing node. Keep the owned node attached through child-client
removal, then release its reference after adapter deletion.

Signed-off-by: Ahmad Byagowi <ahmadexp@xxxxxxxxx>
---
 drivers/i2c/i2c-core-base.c | 24 +++++++++---
 drivers/i2c/i2c-mux.c       | 77 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 93 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 3ec04787a737..f39575ee0244 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1876,12 +1876,22 @@ int devm_i2c_add_adapter(struct device *dev, struct i2c_adapter *adapter)
 }
 EXPORT_SYMBOL_GPL(devm_i2c_add_adapter);
 
-static int i2c_dev_or_parent_fwnode_match(struct device *dev, const void *data)
+static bool i2c_device_match_fwnode(struct device *dev, const void *data)
 {
+	struct fwnode_handle *fwnode = dev_fwnode(dev);
+
 	if (device_match_fwnode(dev, data))
+		return true;
+
+	return !IS_ERR_OR_NULL(fwnode) && fwnode->secondary == data;
+}
+
+static int i2c_dev_or_parent_fwnode_match(struct device *dev, const void *data)
+{
+	if (i2c_device_match_fwnode(dev, data))
 		return 1;
 
-	if (dev->parent && device_match_fwnode(dev->parent, data))
+	if (dev->parent && i2c_device_match_fwnode(dev->parent, data))
 		return 1;
 
 	return 0;
@@ -1891,8 +1901,9 @@ static int i2c_dev_or_parent_fwnode_match(struct device *dev, const void *data)
  * i2c_find_adapter_by_fwnode() - find an i2c_adapter for the fwnode
  * @fwnode: &struct fwnode_handle corresponding to the &struct i2c_adapter
  *
- * Look up and return the &struct i2c_adapter corresponding to the @fwnode.
- * If no adapter can be found, or @fwnode is NULL, this returns NULL.
+ * Look up and return the &struct i2c_adapter corresponding to the @fwnode,
+ * including a secondary firmware node. If no adapter can be found, or
+ * @fwnode is NULL, this returns NULL.
  *
  * The user must call put_device(&adapter->dev) once done with the i2c adapter.
  */
@@ -1922,8 +1933,9 @@ EXPORT_SYMBOL(i2c_find_adapter_by_fwnode);
  * @fwnode: &struct fwnode_handle corresponding to the &struct i2c_adapter
  *
  * Look up and return the &struct i2c_adapter corresponding to the @fwnode,
- * and increment the adapter module's use count. If no adapter can be found,
- * or @fwnode is NULL, this returns NULL.
+ * including a secondary firmware node, and increment the adapter module's
+ * use count. If no adapter can be found, or @fwnode is NULL, this returns
+ * NULL.
  *
  * The user must call i2c_put_adapter(adapter) once done with the i2c adapter.
  * Note that this is different from i2c_find_adapter_by_node().
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 681a201c239b..3bca123907b3 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -20,11 +20,13 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/err.h>
 #include <linux/i2c.h>
 #include <linux/i2c-mux.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 
@@ -33,6 +35,7 @@ struct i2c_mux_priv {
 	struct i2c_adapter adap;
 	struct i2c_algorithm algo;
 	struct i2c_mux_core *muxc;
+	struct fwnode_handle *swnode;
 	u32 chan_id;
 };
 
@@ -264,10 +267,60 @@ static const struct i2c_lock_operations i2c_parent_lock_ops = {
 	.unlock_bus =  i2c_parent_unlock_bus,
 };
 
+static struct fwnode_handle *
+i2c_mux_get_channel_swnode(struct i2c_mux_core *muxc, u32 chan_id)
+{
+	struct fwnode_handle *dev_node = dev_fwnode(muxc->dev);
+	struct fwnode_handle *mux_node, *child = NULL;
+	u32 reg;
+
+	/* A software node supplementing ACPI is the secondary fwnode. */
+	if (!is_software_node(dev_node)) {
+		if (IS_ERR_OR_NULL(dev_node))
+			return NULL;
+		dev_node = dev_node->secondary;
+	}
+	if (!is_software_node(dev_node))
+		return NULL;
+
+	if (muxc->arbitrator)
+		mux_node = fwnode_get_named_child_node(dev_node, "i2c-arb");
+	else if (muxc->gate)
+		mux_node = fwnode_get_named_child_node(dev_node, "i2c-gate");
+	else
+		mux_node = fwnode_get_named_child_node(dev_node, "i2c-mux");
+
+	if (mux_node) {
+		/* A "reg" property indicates an old-style firmware entry. */
+		if (!fwnode_property_read_u32(mux_node, "reg", &reg)) {
+			fwnode_handle_put(mux_node);
+			mux_node = NULL;
+		}
+	}
+
+	if (!mux_node)
+		mux_node = fwnode_handle_get(dev_node);
+	else if (muxc->arbitrator || muxc->gate)
+		child = fwnode_handle_get(mux_node);
+
+	if (!child) {
+		fwnode_for_each_child_node(mux_node, child) {
+			if (fwnode_property_read_u32(child, "reg", &reg))
+				continue;
+			if (chan_id == reg)
+				break;
+		}
+	}
+
+	fwnode_handle_put(mux_node);
+	return child;
+}
+
 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 			u32 force_nr, u32 chan_id)
 {
 	struct i2c_adapter *parent = muxc->parent;
+	struct fwnode_handle *channel_node = NULL;
 	struct i2c_mux_priv *priv;
 	char symlink_name[20];
 	int ret;
@@ -324,8 +377,8 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 		priv->adap.lock_ops = &i2c_parent_lock_ops;
 
 	/*
-	 * Try to populate the mux adapter's of_node, expands to
-	 * nothing if !CONFIG_OF.
+	 * Associate the mux adapter with its DT or software-node channel.
+	 * DT support expands to nothing if !CONFIG_OF.
 	 */
 	if (muxc->dev->of_node) {
 		struct device_node *dev_node = muxc->dev->of_node;
@@ -364,6 +417,8 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 
 		priv->adap.dev.of_node = child;
 		of_node_put(mux_node);
+	} else {
+		channel_node = i2c_mux_get_channel_swnode(muxc, chan_id);
 	}
 
 	/*
@@ -374,6 +429,16 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 				      ACPI_COMPANION(muxc->dev),
 				      chan_id);
 
+	if (channel_node) {
+		ret = device_add_software_node(&priv->adap.dev,
+					       to_software_node(channel_node));
+		if (!ret)
+			priv->swnode = channel_node;
+		fwnode_handle_put(channel_node);
+		if (ret)
+			goto err_free_priv;
+	}
+
 	if (force_nr) {
 		priv->adap.nr = force_nr;
 		ret = i2c_add_numbered_adapter(&priv->adap);
@@ -408,6 +473,8 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 	return 0;
 
 err_free_priv:
+	if (priv->swnode)
+		device_remove_software_node(&priv->adap.dev);
 	kfree(priv);
 	return ret;
 }
@@ -429,7 +496,13 @@ void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
 		sysfs_remove_link(&muxc->dev->kobj, symlink_name);
 
 		sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
+		/*
+		 * Keep the software node through child removal. The adapter
+		 * device is cleared on deletion, so release the software-node
+		 * attachment reference via the saved handle afterwards.
+		 */
 		i2c_del_adapter(adap);
+		fwnode_handle_put(priv->swnode);
 		of_node_put(np);
 		kfree(priv);
 	}
-- 
2.50.1 (Apple Git-155)