linux-kernel - Re: [PATCH net-next 1/3] device property: Introduce fwnode_for_each_available_child_node

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Message-ID: <Zwi6Dn4yJxst4xv2@kekkonen.localdomain>
Date: Fri, 11 Oct 2024 05:39:26 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Daniel Scally <djrscally@...il.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Andrew Lunn <andrew@...n.ch>,
	Florian Fainelli <f.fainelli@...il.com>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] device property: Introduce
 fwnode_for_each_available_child_node_scoped()

Hi Javier,

On Tue, Oct 08, 2024 at 06:10:27PM +0200, Javier Carrasco wrote:
> Introduce the scoped variant of the
> fwnode_for_each_available_child_node() to automatically decrement the
> child's refcount when it goes out of scope, removing the need for
> explicit calls to fwnode_handle_put().
> 
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
> ---
>  include/linux/property.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/property.h b/include/linux/property.h
> index 61fc20e5f81f..b37508ecf606 100644
> --- a/include/linux/property.h
> +++ b/include/linux/property.h
> @@ -168,6 +168,11 @@ struct fwnode_handle *fwnode_get_next_available_child_node(
>  	for (child = fwnode_get_next_available_child_node(fwnode, NULL); child;\
>  	     child = fwnode_get_next_available_child_node(fwnode, child))
>  
> +#define fwnode_for_each_available_child_node_scoped(fwnode, child)	       \
> +	for (struct fwnode_handle *child __free(fwnode_handle) =	       \
> +		fwnode_get_next_available_child_node(fwnode, NULL); child;     \
> +	     child = fwnode_get_next_available_child_node(fwnode, child))
> +

On OF, the implementation of the .get_next_child_node() fwnode op is:

static struct fwnode_handle *
of_fwnode_get_next_child_node(const struct fwnode_handle *fwnode,
                              struct fwnode_handle *child)
{
        return of_fwnode_handle(of_get_next_available_child(to_of_node(fwnode),
                                                            to_of_node(child)));
}

On ACPI we currently have .device_is_available() returning false but that
probably should be returning true instead (it's been virtually unused
previously).

That makes fwnode_get_next_available_child_node() and
fwnode_get_next_child_node() equivalent on both ACPI and OF. Presumably
creating unavailable nodes would be useless on swnode, too.

So my question is: what do we gain by adding all these fwnode_*available()
helpers?

>  struct fwnode_handle *device_get_next_child_node(const struct device *dev,
>  						 struct fwnode_handle *child);

-- 
Regards,

Sakari Ailus