linux-kernel - Re: [PATCH v3 02/10] software node: increase the reference of the swnode by its fwnode

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Message-ID: <CAMRc=MdfbbkWBeAgw3G=k7xgSc8TPhZQ56ks9Or9p9Ah-y5YQw@mail.gmail.com>
Date: Fri, 31 Oct 2025 05:27:10 -0500
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Bartosz Golaszewski <brgl@...ev.pl>, Linus Walleij <linus.walleij@...aro.org>, 
	Daniel Scally <djrscally@...il.com>, Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>, 
	Krzysztof Kozlowski <krzk@...nel.org>, linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-acpi@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v3 02/10] software node: increase the reference of the
 swnode by its fwnode

On Fri, 31 Oct 2025 10:44:46 +0100, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> said:
> On Fri, Oct 31, 2025 at 10:03:47AM +0100, Bartosz Golaszewski wrote:
>> On Fri, Oct 31, 2025 at 9:30 AM Andy Shevchenko
>> <andriy.shevchenko@...ux.intel.com> wrote:
>> > On Thu, Oct 30, 2025 at 03:33:02AM -0700, Bartosz Golaszewski wrote:
>> > > On Thu, 30 Oct 2025 10:34:46 +0100, Andy Shevchenko
>> > > <andriy.shevchenko@...ux.intel.com> said:
>
> ...
>
>> > > Andy: the resulting code after patch 3/10 looks like this:
>> > >
>> > > struct fwnode_handle *refnode;
>> > >
>> > > (...)
>> >
>> > Let's say something like below to be put here
>> >
>> > /*
>> >  * The reference in software node may refer to a node of a different type.
>> >  * Depending on the type we choose either to use software node directly, or
>> >  * delegate that to fwnode API.
>> >  */
>>
>> But this is incorrect: we're not really doing that. We either use the
>> firmware node reference directly OR cast the software node to its
>> firmware node representation. We ALWAYS use the firmware node API
>> below.
>>
>> This really *is* evident from the code but if it'll make you happy and
>> make you sign off on this, I'll add a corrected version.
>
> The comment should answer to the Q: "Why the heck are we calling fwnode APIs here?"
>
>> IMO It's completely redundant.
>
> This is unusual case for swnode API (see other functions, they call directly
> the low-level implementation instead of going to a round via fwnode). That's
> why I insist on a comment of this piece. It may be obvious for you, but the
> unprepared read would be surprised by this inconsistency.
>

I propose to have the following:

+       /*
+        * A software node can reference other software nodes or firmware
+        * nodes (which are the abstraction layer sitting on top of them).
+        * This is done to ensure we can create references to static software
+        * nodes before they're registered with the firmware node framework.
+        * At the time the reference is being resolved, we expect the swnodes
+        * in question to already have been registered and to be backed by
+        * a firmware node. This is why we use the fwnode API below to read the
+        * relevant properties and bump the reference count.
+        */

This at least adds relevant information on *why* we're using the fwnode API.

Bart