linux-kernel - Re: [PATCH v2] media: i2c: thp7312: use fwnode_for_each_child

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Message-ID: <20250321104100.GC25483@pendragon.ideasonboard.com>
Date: Fri, 21 Mar 2025 12:41:00 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
	Paul Elder <paul.elder@...asonboard.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v2] media: i2c: thp7312: use fwnode_for_each_child_node()

Hi Matti,

Thank you for the patch.

On Fri, Mar 21, 2025 at 10:58:27AM +0200, Matti Vaittinen wrote:
> When fwnode_for_each_available_child_node() is used on the device-tree
> backed systems, it renders to same operation as the
> fwnode_for_each_child_node(), because the fwnode_for_each_child_node()
> does only iterate through those device-tree nodes which are available.

This makes me wonder why the OF backend implements
fwnode_for_each_child_node() as fwnode_for_each_available_child_node().
Is that on purpose, or is it a bug ?

> The thp7312 uses the fwnode_for_each_available_child_node() to look up
> and handle nodes with specific names. This means the code is used only
> on the device-tree backed systems because the node names have little
> meaning on ACPI or swnode backed systems.
> 
> Use the fwnode_for_each_child_node() instead of the
> fwnode_for_each_available_child_node() In order to make it clearly
> visible that the 'availability' of the nodes does not need to be
> explicitly considered here. This will also make it clearly visible that
> the code in this driver is suitable candidate to be converted to use the
> new fwnode_for_each_named_child_node()[2] when it gets merged.
> 
> [1]: https://lore.kernel.org/all/Z9rhfJUlCbi7kA2m@kekkonen.localdomain/
> [2]: https://lore.kernel.org/all/9c3880f74476436f39d796b5c10c540ae50b722c.1742225817.git.mazziesaccount@gmail.com/
> 
> Suggested-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> 
> ---
> Revision history:
> v1 => v2:
>  - rephrase the commit message to not claim the 'availability' has no
>    well defined meaning on the DT backed systems. Instead, explain that
>    the fwnode_for_each_available_child_node() only iterates through the
>    available nodes on the DT backed systems and is thus functionally
>    equivalent to the fwnode_for_each_child_node().
> 
> NOTE: The change is compile tested only! Proper testing and reviewing is
> highly appreciated (as always).
> ---
>  drivers/media/i2c/thp7312.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/thp7312.c b/drivers/media/i2c/thp7312.c
> index 8852c56431fe..4b66f64f8d65 100644
> --- a/drivers/media/i2c/thp7312.c
> +++ b/drivers/media/i2c/thp7312.c
> @@ -2067,7 +2067,7 @@ static int thp7312_parse_dt(struct thp7312_device *thp7312)
>  		return -EINVAL;
>  	}
>  
> -	fwnode_for_each_available_child_node(sensors, node) {
> +	fwnode_for_each_child_node(sensors, node) {
>  		if (fwnode_name_eq(node, "sensor")) {
>  			if (!thp7312_sensor_parse_dt(thp7312, node))
>  				num_sensors++;
> 
> base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6

-- 
Regards,

Laurent Pinchart