linux-kernel - Re: [PATCH v1 3/4] ACPI: property: Do not pass NULL handles to acpi_attach

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Message-ID: <CAJZ5v0hPjWHwSSc9cTdC76RypWGPUYrkqw+W3Vb52uy_UJpk9A@mail.gmail.com>
Date: Mon, 15 Sep 2025 14:57:31 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Linux ACPI <linux-acpi@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	Mika Westerberg <mika.westerberg@...ux.intel.com>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v1 3/4] ACPI: property: Do not pass NULL handles to acpi_attach_data()

Hi Sakari,

On Mon, Sep 15, 2025 at 1:50 PM Sakari Ailus
<sakari.ailus@...ux.intel.com> wrote:
>
> Hi Rafael,
>
> On Fri, Sep 12, 2025 at 09:42:55PM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > In certain circumstances, the ACPI handle of a data-only node may be
> > NULL, in which case it does not make sense to attempt to attach that
> > node to an ACPI namespace object, so update the code to avoid attempts
> > to do so.
> >
> > This prevents confusing and unuseful error messages from being printed.
> >
> > Also document the fact that the ACPI handle of a data-only node may be
> > NULL, and when that happens, in a code comment.
> >
> > In addition, make acpi_add_nondev_subnodes() print a diagnostic message
> > for each data-only node with an unknown ACPI namespace scope.
> >
> > Fixes: 1d52f10917a7 ("ACPI: property: Tie data nodes to acpi handles")
> > Cc: 6.0+ <stable@...r.kernel.org> # 6.0+
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/acpi/property.c |   12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > --- a/drivers/acpi/property.c
> > +++ b/drivers/acpi/property.c
> > @@ -124,6 +124,10 @@ static bool acpi_nondev_subnode_extract(
> >               result = true;
> >
> >       if (result) {
> > +             /*
> > +              * This will be NULL if the desc package is embedded in an outer
> > +              * _DSD-equivalent package and its scope cannot be determined.
> > +              */
>
> I think indeed this happens in particular when when references to
> non-device nodes; there's no handle because when you get is basically a
> dynamically allocated copy of a node.

I know for a fact that this happens, that's why I'm adding the comment here.

> >               dn->handle = handle;
> >               dn->data.pointer = desc;
> >               list_add_tail(&dn->sibling, list);
> > @@ -245,6 +249,8 @@ static bool acpi_add_nondev_subnodes(acp
> >                        * strings because there is no way to build full
> >                        * pathnames out of them.
> >                        */
> > +                     acpi_handle_info(scope, "Unknown namespace scope of node %s\n",
> > +                                      link->package.elements[0].string.pointer);
> >                       desc = &link->package.elements[1];
> >                       result = acpi_nondev_subnode_extract(desc, NULL, link,
> >                                                            list, parent);
> > @@ -408,6 +414,9 @@ static void acpi_untie_nondev_subnodes(s
> >       struct acpi_data_node *dn;
> >
> >       list_for_each_entry(dn, &data->subnodes, sibling) {
> > +             if (!dn->handle)
> > +                     continue;
> > +
> >               acpi_detach_data(dn->handle, acpi_nondev_subnode_tag);
> >
> >               acpi_untie_nondev_subnodes(&dn->data);
> > @@ -422,6 +431,9 @@ static bool acpi_tie_nondev_subnodes(str
> >               acpi_status status;
> >               bool ret;
> >
> > +             if (!dn->handle)
> > +                     continue;
> > +
> >               status = acpi_attach_data(dn->handle, acpi_nondev_subnode_tag, dn);
> >               if (ACPI_FAILURE(status) && status != AE_ALREADY_EXISTS) {
> >                       acpi_handle_err(dn->handle, "Can't tag data node\n");
> >
> >
> >
>
> --
> Kind regards,
>
> Sakari Ailus