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

[Danilo Krummrich]

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.

> 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>