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

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Message-ID: <Z_T8N8aHR-2OzHAO@kekkonen.localdomain>
Date: Tue, 8 Apr 2025 10:36:39 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	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
Subject: Re: [PATCH v2] media: i2c: thp7312: use fwnode_for_each_child_node()

Hei Laurent, Matti,

On Tue, Apr 08, 2025 at 01:26:42PM +0300, Matti Vaittinen wrote:
> On 08/04/2025 13:12, Laurent Pinchart wrote:
> > 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@...ux.intel.com>
> > > 
> > > 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.
> > 
> 
> I assume the fwnode_for_each_available_child_node() still makes sense for
> ACPI backed users, no?

Not really (see my earlier explanation in
<Z9mQPJwnKAkPHriT@...konen.localdomain>). I think all the *available* stuff
should be removed from include/linux/property.h, apart from
fwnode_device_is_availble(), which should be turned to work on struct
device to signal its availability for device nodes only.

-- 
Terveisin,

Sakari Ailus