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

[Laurent Pinchart]

Hi Sakari,

On Tue, Apr 08, 2025 at 08:48:45AM +0000, Sakari Ailus wrote:
> On Fri, Mar 21, 2025 at 12:41:00PM +0200, Laurent Pinchart wrote:
> > 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@xxxxxxxxxxxxxxx>
> 
> We should also change the documentation of the fwnode API accordingly.

Does that also mean that the fwnode_for_each_available_child_node()
function will be dropped ? It's used by few drivers (5 in addition to
the thp7312 driver, plus 3 call sites in drivers/base/core.c), so a
patch series to drop it should be easy.

> > > 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@xxxxxxxxx/
> > > 
> > > Suggested-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
> > > 
> > > ---
> > > 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