Re: [PATCH v5 3/8] software node: allow referencing firmware nodes

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Bartosz,

Thanks for the update.

On Wed, Nov 05, 2025 at 09:47:34AM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.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: add a second pointer to
> struct software_node_ref_args of type struct fwnode_handle. The core
> swnode code will first check the swnode pointer and if it's NULL, it
> will assume the fwnode pointer should be set.
> 
> Software node graphs remain the same, as in: the remote endpoints still
> have to be software nodes.
> 
> Acked-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>

But see below...

> ---
>  drivers/base/swnode.c    | 24 ++++++++++++++++++++++--
>  include/linux/property.h | 13 ++++++++++---
>  2 files changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
> index 6b1ee75a908fbf272f29dbe65529ce69ce03a021..44710339255ffba1766f5984b2898a5fb4436557 100644
> --- a/drivers/base/swnode.c
> +++ b/drivers/base/swnode.c
> @@ -535,7 +535,24 @@ software_node_get_reference_args(const struct fwnode_handle *fwnode,
>  	ref_array = prop->pointer;
>  	ref = &ref_array[index];
>  
> -	refnode = software_node_fwnode(ref->node);
> +	/*
> +	 * A software node can reference other software nodes or firmware
> +	 * nodes (which are the abstraction layer sitting on top of them).
> +	 * This is done to ensure we can create references to static software
> +	 * nodes before they're registered with the firmware node framework.
> +	 * At the time the reference is being resolved, we expect the swnodes
> +	 * in question to already have been registered and to be backed by
> +	 * a firmware node. This is why we use the fwnode API below to read the
> +	 * relevant properties and bump the reference count.
> +	 */
> +
> +	if (ref->swnode)
> +		refnode = software_node_fwnode(ref->swnode);
> +	else if (ref->fwnode)
> +		refnode = ref->fwnode;
> +	else
> +		return -EINVAL;
> +
>  	if (!refnode)
>  		return -ENOENT;
>  
> @@ -633,7 +650,10 @@ software_node_graph_get_remote_endpoint(const struct fwnode_handle *fwnode)
>  
>  	ref = prop->pointer;
>  
> -	return software_node_get(software_node_fwnode(ref[0].node));
> +	if (!ref->swnode)
> +		return NULL;
> +
> +	return software_node_get(software_node_fwnode(ref[0].swnode));

This could be:

	return software_node_get(software_node_fwnode(ref->swnode));

>  }
>  
>  static struct fwnode_handle *
> diff --git a/include/linux/property.h b/include/linux/property.h
> index 50b26589dd70d1756f3b8644255c24a011e2617c..272bfbdea7bf4ab1143159fa49fc29dcdde0ef9d 100644
> --- a/include/linux/property.h
> +++ b/include/linux/property.h
> @@ -355,19 +355,26 @@ struct software_node;
>  
>  /**
>   * 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;
> +	const struct software_node *swnode;
> +	struct fwnode_handle *fwnode;
>  	unsigned int nargs;
>  	u64 args[NR_FWNODE_REFERENCE_ARGS];
>  };
>  
>  #define SOFTWARE_NODE_REFERENCE(_ref_, ...)			\
>  (const struct software_node_ref_args) {				\
> -	.node = _ref_,						\
> +	.swnode = _Generic(_ref_,				\
> +			   const struct software_node *: _ref_,	\
> +			   default: NULL),			\
> +	.fwnode = _Generic(_ref_,				\
> +			   struct fwnode_handle *: _ref_,	\
> +			   default: NULL),			\
>  	.nargs = COUNT_ARGS(__VA_ARGS__),			\
>  	.args = { __VA_ARGS__ },				\
>  }
> 

-- 
Kind regards,

Sakari Ailus