linux-kernel - Re: [PATCH 3/9] software node: allow referencing firmware nodes

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Message-ID: <aPPqWTohCi-Huvfq@ashevche-desk.local>
Date: Sat, 18 Oct 2025 22:28:25 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Daniel Scally <djrscally@...il.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Krzysztof Kozlowski <krzk@...nel.org>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 3/9] software node: allow referencing firmware nodes


On Mon, Oct 06, 2025 at 03:00:18PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> At the moment software nodes can only reference other software nodes.
> This is a limitation for devices created, for instance, on the auxiliary
> bus with a dynamic software node attached which cannot reference devices
> the firmware node of which is "real" (as an OF node or otherwise).
> 
> Make it possible for a software node to reference all firmware nodes in
> addition to static software nodes. To that end: use a union of different
> pointers in struct software_node_ref_args and add an enum indicating
> what kind of reference given instance of it is. Rework the helper macros
> and deprecate the existing ones whose names don't indicate the reference
> type.
> 
> Software node graphs remain the same, as in: the remote endpoints still
> have to be software nodes.

...

> +enum software_node_ref_type {
> +	/* References a software node. */
> +	SOFTWARE_NODE_REF_SWNODE = 0,


I don't see why we need an explicit value here.

> +	/* References a firmware node. */
> +	SOFTWARE_NODE_REF_FWNODE,
> +};

...

>  /**
>   * struct software_node_ref_args - Reference property with additional arguments
> - * @node: Reference to a software node
> + * @swnode: Reference to a software node
> + * @fwnode: Alternative reference to a firmware node handle
>   * @nargs: Number of elements in @args array
>   * @args: Integer arguments
>   */
>  struct software_node_ref_args {
> -	const struct software_node *node;
> +	enum software_node_ref_type type;
> +	union {
> +		const struct software_node *swnode;
> +		struct fwnode_handle *fwnode;
> +	};

Can't we always have an fwnode reference?

>  	unsigned int nargs;
>  	u64 args[NR_FWNODE_REFERENCE_ARGS];
>  };

-- 
With Best Regards,
Andy Shevchenko