Re: [PATCH v8 1/2] i2c: mux: Factor out channel node lookup

[Andy Shevchenko]

On Mon, Aug 31, 2026 at 10:22:06AM -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 = muxc->dev->of_node;

It's better for maintenance to split assignment (due to validation below).

	struct device_node *dev_node;

> +	struct device_node *mux_node, *child;
> +	u32 reg;
> +	int ret;

// also use getter
	dev_node = dev_of_node(dev);

> +	if (!dev_node)
> +		return NULL;

Looking at the code, it's NULL-aware as far as I can see and this check is just
a shortcut.

> +	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