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

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Message-ID: <aMh6gJtQcRgqgYd6@kekkonen.localdomain>
Date: Mon, 15 Sep 2025 23:43:44 +0300
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: 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 Rafael,

On Mon, Sep 15, 2025 at 02:57:31PM +0200, Rafael J. Wysocki wrote:
> 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.

I wanted to say it could be helpful to have this written in the comment.

> 
> > >               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