Re: [PATCH] mfd: core: Preserve OF node when ACPI handle is present

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Feb 26, 2026 at 09:27:50AM +0200, Andy Shevchenko wrote:
> On Wed, Feb 25, 2026 at 03:21:05PM -0800, Brian Mak wrote:
> > Switch device_set_node back to ACPI_COMPANION_SET, so that the ACPI
> 
> device_set_node()
> ACPI_COMPANION_SET() // but see below.
> 
> > fwnode does not overwrite the of_node with NULL.
> 
> > This allows MFD children with both OF nodes and ACPI handles to have OF
> > nodes again.
> 
> Do you have a real use case? Can you elaborate more (platform, drivers
> being involved, et cetera)?

Even more thinking on this it looks like a violation of the levels of
the fwnodes. The current design was not expecting the ACPI *and* OF node
to appear in the list. They both are considered "primary" from the design
point of view.

In your case it seems like an OF node comes from likely DT overlay and
messes up this logic (although it can be considered 'secondary' semantically).
But the proposed patch is not a solution, it's a band-aid.

TL;DR: if there is a use case that worked before (please elaborate),
the patch as a quick fix looks okay, but with FIXME added and open coded logic:

	/*
	 * ...description of use case...
	 *
	 * FIXME: The fwnode design doesn't allow proper sharing and stacking.
	 * Eventually this should become some device fwnode API call that will
	 * prepend the list of fwnodes (making ACPI one "primary" in that sense).
	 */
	if (adev)
		set_primary_fwnode(&pdev->dev, acpi_fwnode_handle(adev));
	else if (parent)
		set_primary_fwnode(&pdev->dev, acpi_fwnode_handle(parent));

...

> > -	device_set_node(&pdev->dev, acpi_fwnode_handle(adev ?: parent));
> > +	ACPI_COMPANION_SET(&pdev->dev, adev ?: parent);
> 
> As a quick fix this may be fine, but it needs a big FIXME explaining that this
> is actually a design limitation of fwnode that doesn't allow proper sharing
> and stacking.
> 
> Bouncing back to ACPI_COMPANION_SET() also doesn't feel right as it hides
> the real thing here, and real thing is the primary/secondary fwnode types
> that we need to care of. Just call set_primary_fwnode() directly. It helps
> also to get rid of ACPI_COMPANION_SET() calls where it may be replaced with
> simple device_set_node().

-- 
With Best Regards,
Andy Shevchenko