Re: [PATCH v2] media: i2c: thp7312: use fwnode_for_each_child_node()

Sakari Ailus
2025-04-08T08:48:50Z

Hi Laurent, Matti,

On Fri, Mar 21, 2025 at 12:41:00PM +0200, Laurent Pinchart wrote:
> 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 ?

I discussed this with Rafael and he didn't recall why the original
implementation was like that. The general direction later on has been not
to present unavailable nodes over the fwnode interface.

So I'd say:

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

We should also change the documentation of the fwnode API accordingly.

>
> > 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@linux.intel.com>
> > Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.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,

Sakari Ailus