Re: [PATCH v7 2/3] i2c: mux: Factor out channel node lookup

[Peter Rosin <peda@lysator.liu.se>]

Hi!

Den Sun, Aug 23, 2026 at 09:34:37AM -0700, skrev 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 | 84 +++++++++++++++++++++++--------------------
>  1 file changed, 46 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
> index 68a4c34b5987..a8b94b97a725 100644
> --- a/drivers/i2c/i2c-mux.c
> +++ b/drivers/i2c/i2c-mux.c
> @@ -264,6 +264,51 @@ 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 = muxc->dev->of_node;
> +	struct device_node *mux_node, *child = NULL;
> +	u32 reg;
> +	int ret;
> +
> +	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)
> +		child = of_node_get(mux_node);

You can return early here with "return mux_node;" (which also
obviates the need for the above " = NULL"-initializer and the
below "if (!child)"-test).

Cheers,
Peter

> +
> +	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;
> +		}
> +	}
> +
> +	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 +372,7 @@ 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)
>