[PATCH v9 0/2] i2c: mux: Propagate firmware nodes to channel adapters

[PATCH v9 0/2] i2c: mux: Propagate firmware nodes to channel adapters

[Ahmad Byagowi]

Device Tree channel nodes are associated with the adapters created by
i2c-mux, but equivalent firmware-node descriptions are not. Convert the
existing lookup to generic firmware-node operations so software-node and
ACPI descriptions can use the same property traversal.

This is the remaining I2C prerequisite split out of the Time Card series.
The channel-node leak fix from v7 was applied to i2c-next as commit
385c7af4e3b9 ("i2c: mux: Fix channel node leak on adapter add failure"), so
it is no longer included here. The first patch factors the Device Tree
lookup into a helper without changing behavior. The second converts the
helper and node lifetime handling to generic firmware-node operations.

The existing acpi_preset_companion() call remains in place after the generic
lookup. A separate reference to the node returned by that lookup is retained
because ACPI companion setup may replace the adapter's primary firmware
node. The dependent ptp_ocp board profiles will be resent to net-next after
the LED and I2C prerequisites land.

Changes since v8:
  - Split the dev_node declaration from its assignment and use
    dev_of_node() in the Device Tree helper, as suggested by Andy
    Shevchenko.
  - Preserve the split declaration and assignment when converting the
    helper to dev_fwnode().
  - Leave broader __free(fwnode_handle) cleanup for a separate follow-up.

Validation:
  - git diff --check
  - strict checkpatch with an 80-column limit
  - x86-64 GCC W=1 object build of drivers/i2c/i2c-mux.o
  - mailbox replay onto the declared base with an identical resulting tree

v8: https://lore.kernel.org/r/cover.1788181174.git.ahmadexp@gmail.com/

Ahmad Byagowi (2):
  i2c: mux: Factor out channel node lookup
  i2c: mux: Propagate firmware nodes to channel adapters

 drivers/i2c/i2c-mux.c | 97 +++++++++++++++++++++++--------------------
 1 file changed, 51 insertions(+), 46 deletions(-)


base-commit: 1f3e66348d2527c31b9bedb0b4d9e28bdad9bc83
-- 
2.50.1 (Apple Git-155)

[PATCH v9 1/2] i2c: mux: Factor out channel node lookup

[Ahmad Byagowi]

Move the existing Device Tree channel-node lookup into a helper in
preparation for using generic firmware-node operations.

This is a pure refactoring with no functional change.

Signed-off-by: Ahmad Byagowi <ahmadexp@gmail.com>
---
 drivers/i2c/i2c-mux.c | 83 +++++++++++++++++++++++--------------------
 1 file changed, 45 insertions(+), 38 deletions(-)

diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 68a4c34b5987..37529c7627a6 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -264,6 +264,50 @@ static const struct i2c_lock_operations i2c_parent_lock_ops = {
 	.unlock_bus =  i2c_parent_unlock_bus,
 };
 
+static struct device_node *
+i2c_mux_get_channel_node(struct i2c_mux_core *muxc, u32 chan_id)
+{
+	struct device_node *dev_node;
+	struct device_node *mux_node, *child;
+	u32 reg;
+	int ret;
+
+	dev_node = dev_of_node(muxc->dev);
+	if (!dev_node)
+		return NULL;
+
+	if (muxc->arbitrator)
+		mux_node = of_get_child_by_name(dev_node, "i2c-arb");
+	else if (muxc->gate)
+		mux_node = of_get_child_by_name(dev_node, "i2c-gate");
+	else
+		mux_node = of_get_child_by_name(dev_node, "i2c-mux");
+
+	if (mux_node) {
+		/* A "reg" property indicates an old-style DT entry */
+		if (!of_property_read_u32(mux_node, "reg", &reg)) {
+			of_node_put(mux_node);
+			mux_node = NULL;
+		}
+	}
+
+	if (!mux_node)
+		mux_node = of_node_get(dev_node);
+	else if (muxc->arbitrator || muxc->gate)
+		return mux_node;
+
+	for_each_child_of_node(mux_node, child) {
+		ret = of_property_read_u32(child, "reg", &reg);
+		if (ret)
+			continue;
+		if (chan_id == reg)
+			break;
+	}
+
+	of_node_put(mux_node);
+	return child;
+}
+
 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 			u32 force_nr, u32 chan_id)
 {
@@ -327,44 +371,7 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 	 * Try to populate the mux adapter's of_node, expands to
 	 * nothing if !CONFIG_OF.
 	 */
-	if (muxc->dev->of_node) {
-		struct device_node *dev_node = muxc->dev->of_node;
-		struct device_node *mux_node, *child = NULL;
-		u32 reg;
-
-		if (muxc->arbitrator)
-			mux_node = of_get_child_by_name(dev_node, "i2c-arb");
-		else if (muxc->gate)
-			mux_node = of_get_child_by_name(dev_node, "i2c-gate");
-		else
-			mux_node = of_get_child_by_name(dev_node, "i2c-mux");
-
-		if (mux_node) {
-			/* A "reg" property indicates an old-style DT entry */
-			if (!of_property_read_u32(mux_node, "reg", &reg)) {
-				of_node_put(mux_node);
-				mux_node = NULL;
-			}
-		}
-
-		if (!mux_node)
-			mux_node = of_node_get(dev_node);
-		else if (muxc->arbitrator || muxc->gate)
-			child = of_node_get(mux_node);
-
-		if (!child) {
-			for_each_child_of_node(mux_node, child) {
-				ret = of_property_read_u32(child, "reg", &reg);
-				if (ret)
-					continue;
-				if (chan_id == reg)
-					break;
-			}
-		}
-
-		priv->adap.dev.of_node = child;
-		of_node_put(mux_node);
-	}
+	priv->adap.dev.of_node = i2c_mux_get_channel_node(muxc, chan_id);
 
 	/*
 	 * Associate the mux channel with an ACPI node.
-- 
2.50.1 (Apple Git-155)

Re: [PATCH v9 1/2] i2c: mux: Factor out channel node lookup

[Andy Shevchenko]

On Thu, Sep 03, 2026 at 12:40:55PM -0700, Ahmad Byagowi wrote:
> Move the existing Device Tree channel-node lookup into a helper in
> preparation for using generic firmware-node operations.
> 
> This is a pure refactoring with no functional change.

...

> +static struct device_node *
> +i2c_mux_get_channel_node(struct i2c_mux_core *muxc, u32 chan_id)
> +{
> +	struct device_node *dev_node;
> +	struct device_node *mux_node, *child;

Now all three can be defined in a single line.

> +	u32 reg;
> +	int ret;
> +
> +	dev_node = dev_of_node(muxc->dev);
> +	if (!dev_node)
> +		return NULL;
> +
> +	if (muxc->arbitrator)
> +		mux_node = of_get_child_by_name(dev_node, "i2c-arb");
> +	else if (muxc->gate)
> +		mux_node = of_get_child_by_name(dev_node, "i2c-gate");
> +	else
> +		mux_node = of_get_child_by_name(dev_node, "i2c-mux");
> +
> +	if (mux_node) {
> +		/* A "reg" property indicates an old-style DT entry */
> +		if (!of_property_read_u32(mux_node, "reg", &reg)) {
> +			of_node_put(mux_node);
> +			mux_node = NULL;
> +		}
> +	}
> +
> +	if (!mux_node)
> +		mux_node = of_node_get(dev_node);
> +	else if (muxc->arbitrator || muxc->gate)
> +		return mux_node;
> +
> +	for_each_child_of_node(mux_node, child) {
> +		ret = of_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			continue;
> +		if (chan_id == reg)
> +			break;
> +	}
> +
> +	of_node_put(mux_node);
> +	return child;
> +}

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v9 1/2] i2c: mux: Factor out channel node lookup

[Peter Rosin]

Den Thu, Sep 03, 2026 at 10:58:53PM +0300, skrev Andy Shevchenko:
> On Thu, Sep 03, 2026 at 12:40:55PM -0700, Ahmad Byagowi wrote:
> > Move the existing Device Tree channel-node lookup into a helper in
> > preparation for using generic firmware-node operations.
> > 
> > This is a pure refactoring with no functional change.
> 
> ...
> 
> > +static struct device_node *
> > +i2c_mux_get_channel_node(struct i2c_mux_core *muxc, u32 chan_id)
> > +{
> > +	struct device_node *dev_node;
> > +	struct device_node *mux_node, *child;
> 
> Now all three can be defined in a single line.

They could, but three is a crowd. So, if you bother to send an update,
please use one declaration per line instead to make future diffs
clearer.

Cheers,
Peter

Re: [PATCH v9 1/2] i2c: mux: Factor out channel node lookup

[Andy Shevchenko]

On Sat, Sep 05, 2026 at 07:46:36AM +0200, Peter Rosin wrote:
> Den Thu, Sep 03, 2026 at 10:58:53PM +0300, skrev Andy Shevchenko:
> > On Thu, Sep 03, 2026 at 12:40:55PM -0700, Ahmad Byagowi wrote:

...

> > > +	struct device_node *dev_node;
> > > +	struct device_node *mux_node, *child;
> > 
> > Now all three can be defined in a single line.
> 
> They could, but three is a crowd. So, if you bother to send an update,
> please use one declaration per line instead to make future diffs
> clearer.

True, but it can reduce churn between these two patches if placed on
a single line. Whatever, it's a bikeshedding, so go with what Peter
prefers (as he is a maintainer IIRC of this code).

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v9 1/2] i2c: mux: Factor out channel node lookup

[Ahmad Byagowi]

Peter, Andy,

Thanks for clarifying. I'll use one declaration per line for dev_node,
mux_node, and child in both patches in the next revision.

Regards,
Ahmad

[PATCH v9 2/2] i2c: mux: Propagate firmware nodes to channel adapters

[Ahmad Byagowi]

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

Use generic firmware-node operations for the existing channel lookup
and associate the returned node with the adapter. Do not restrict the
lookup by firmware-node type, so Device Tree, software nodes, and ACPI
descriptions all follow the same property traversal. The existing
acpi_preset_companion() call remains in place for the standard ACPI
channel association.

Keep a separate reference to the node returned by the generic lookup
because acpi_preset_companion() may replace the device's primary
firmware node. Release the saved reference after adapter deletion.

Signed-off-by: Ahmad Byagowi <ahmadexp@gmail.com>
---
 drivers/i2c/i2c-mux.c | 44 +++++++++++++++++++++----------------------
 1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 37529c7627a6..e0b0116d5b6d 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -24,7 +24,7 @@
 #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 +33,7 @@ struct i2c_mux_priv {
 	struct i2c_adapter adap;
 	struct i2c_algorithm algo;
 	struct i2c_mux_core *muxc;
+	struct fwnode_handle *channel_node;
 	u32 chan_id;
 };
 
@@ -264,47 +265,47 @@ static const struct i2c_lock_operations i2c_parent_lock_ops = {
 	.unlock_bus =  i2c_parent_unlock_bus,
 };
 
-static struct device_node *
+static struct fwnode_handle *
 i2c_mux_get_channel_node(struct i2c_mux_core *muxc, u32 chan_id)
 {
-	struct device_node *dev_node;
-	struct device_node *mux_node, *child;
+	struct fwnode_handle *dev_node;
+	struct fwnode_handle *mux_node, *child;
 	u32 reg;
 	int ret;
 
-	dev_node = dev_of_node(muxc->dev);
+	dev_node = dev_fwnode(muxc->dev);
 	if (!dev_node)
 		return NULL;
 
 	if (muxc->arbitrator)
-		mux_node = of_get_child_by_name(dev_node, "i2c-arb");
+		mux_node = fwnode_get_named_child_node(dev_node, "i2c-arb");
 	else if (muxc->gate)
-		mux_node = of_get_child_by_name(dev_node, "i2c-gate");
+		mux_node = fwnode_get_named_child_node(dev_node, "i2c-gate");
 	else
-		mux_node = of_get_child_by_name(dev_node, "i2c-mux");
+		mux_node = fwnode_get_named_child_node(dev_node, "i2c-mux");
 
 	if (mux_node) {
-		/* A "reg" property indicates an old-style DT entry */
-		if (!of_property_read_u32(mux_node, "reg", &reg)) {
-			of_node_put(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 = of_node_get(dev_node);
+		mux_node = fwnode_handle_get(dev_node);
 	else if (muxc->arbitrator || muxc->gate)
 		return mux_node;
 
-	for_each_child_of_node(mux_node, child) {
-		ret = of_property_read_u32(child, "reg", &reg);
+	fwnode_for_each_child_node(mux_node, child) {
+		ret = fwnode_property_read_u32(child, "reg", &reg);
 		if (ret)
 			continue;
 		if (chan_id == reg)
 			break;
 	}
 
-	of_node_put(mux_node);
+	fwnode_handle_put(mux_node);
 	return child;
 }
 
@@ -367,11 +368,9 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 	else
 		priv->adap.lock_ops = &i2c_parent_lock_ops;
 
-	/*
-	 * Try to populate the mux adapter's of_node, expands to
-	 * nothing if !CONFIG_OF.
-	 */
-	priv->adap.dev.of_node = i2c_mux_get_channel_node(muxc, chan_id);
+	/* Associate the mux adapter with its channel firmware node. */
+	priv->channel_node = i2c_mux_get_channel_node(muxc, chan_id);
+	device_set_node(&priv->adap.dev, priv->channel_node);
 
 	/*
 	 * Associate the mux channel with an ACPI node.
@@ -415,7 +414,7 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 	return 0;
 
 err_free_priv:
-	of_node_put(priv->adap.dev.of_node);
+	fwnode_handle_put(priv->channel_node);
 	kfree(priv);
 	return ret;
 }
@@ -428,7 +427,6 @@ void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
 	while (muxc->num_adapters) {
 		struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
 		struct i2c_mux_priv *priv = adap->algo_data;
-		struct device_node *np = adap->dev.of_node;
 
 		muxc->adapter[muxc->num_adapters] = NULL;
 
@@ -438,7 +436,7 @@ void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
 
 		sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
 		i2c_del_adapter(adap);
-		of_node_put(np);
+		fwnode_handle_put(priv->channel_node);
 		kfree(priv);
 	}
 }
-- 
2.50.1 (Apple Git-155)