Re: [PATCH v3] driver core/ACPI: Introduce companion_bus_register()

[Rafael J. Wysocki (Intel)]

On Fri, Sep 25, 2026 at 1:34 PM Danilo Krummrich <dakr@xxxxxxxxxx> wrote:
>
> On Fri Sep 25, 2026 at 11:23 AM CEST, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > The ACPI bus type does not allow drivers to be matched to devices, so
> > the sysfs attributes related to drivers created for it are useless and
> > their existence is confusing.
> >
> > Moreover, it is better to prevent drivers from being registered and
> > looked up for a bus like that.
> >
> > To allow skipping the creation of those sysfs attributes and preventing
> > driver registration and lookup for the ACPI bus type, introduce a
> > "companion" bus type concept and add a special registration function
> > for registering "companion" bus types, companion_bus_register().
> >
> > The "drivers" directory under the ACPI bus type is still needed because
> > there are versions of systemd that depend on it [1].
>
> Maybe we should also add a brief note above kset_create_and_add("drivers", ...)
> why we retain the directory even if !use_drivers.

Yeah, won't hurt.  I'll add one, or somebody will try to "fix" it in the future.

> > Link: https://lore.kernel.org/linux-acpi/SN6PR02MB41575266A4580339E186E5D9D4812@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ [1]
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> Reviewed-by: Danilo Krummrich <dakr@xxxxxxxxxx>

Thanks!