Re: [PATCH v2] driver core/ACPI: Introduce companion_bus_register()

[Rafael J. Wysocki (Intel)]

On Wed, Sep 23, 2026 at 7:06 PM Michael Kelley <mhklinux@xxxxxxxxxxx> wrote:
>
> From: Rafael J. Wysocki <rafael@xxxxxxxxxx> Sent: Wednesday, September 9, 2026 9:41 AM
> >
> > The ACPI bus type does not allow drivers to be registered, so the sysfs
> > attributes related to drivers created for it and its devices are
> > useless, and its drivers/ directory is always empty.  All of that is
> > confusing and wasteful.
> >
> > To allow skipping the creation of those sysfs attributes, introduce a
> > "companion" bus type concept and add a special registration function for
> > registering "companion" bus types, companion_bus_register().
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> As a heads up, this patch breaks Linux guests booting on Hyper-V.
> Something goes wrong in the VMBus driver getting loaded and
> initialized (drivers/hv/vmbus_drv.c).

This patch doesn't affect anything except for bus registration and
driver addition and lookup for the ACPI bus type.

> It may be that the VMBus
> driver is doing something wrong or making an invalid assumption.
> I'll debug the problem today or tomorrow, but any insight you can
> offer would be appreciated. I'm working with linux-next20260921.

No idea what's going on.