linux-kernel - Re: [PATCH 0/2] thunderbolt: Link USB4 ports to their USB Type-C connectors

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Date:   Wed, 20 Apr 2022 09:39:25 -0700
From:   Won Chung <wonchung@...gle.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Alexander Usyskin <alexander.usyskin@...el.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Benson Leung <bleung@...omium.org>,
        Prashant Malani <pmalani@...omium.org>,
        Daniele Ceraolo Spurio <daniele.ceraolospurio@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] thunderbolt: Link USB4 ports to their USB Type-C connectors

On Wed, Apr 20, 2022 at 3:54 AM Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
>
> Hi,
>
> On Mon, Apr 18, 2022 at 05:59:30PM +0000, Won Chung wrote:
> > Currently, USB port is linked to Type C connector, using the component
> > framework, if they share the same _PLD fields from ACPI table. Type C
> > port-mapper searches for devices with the same _PLD values, and
> > aggregate them as components.
> >
> > When there is another device that share the same _PLD but does not
> > registers a component, Type C connector (component master) would never
> > be bound due to a component match entry device without a component
> > registered. There exists some cases where USB4 port also shares the same
> > _PLD with USB port and Type C connector, so we need to register a
> > component for USB4 ports too, linking USB4 port with Type C connector.
> > Otherwise, link between USB port and Type C connector would not
> > work either.
> >
> > Due to the nature of the component framework, all registered components
> > are shared by all component match despite the relevance. MEI subsystems
> > also use the component framework to bind to i915 driver, which try to
> > match components registered by USB ports and USB4 ports. This can be
> > problematic since MEI assumes that there is a driver bound to the
> > component device, while USB4 port does not bind to any drivers. MEI's
> > component match callback functions should handle such case to avoid NULL
> > pointer dereference when USB4 port registers a component.
> >
> > In summary this patch series
> > 1. Fixes MEI subsystem's component match callbacks to handle a component
> > device without any driver bound
> > 2. Registers a component for USB4 ports to link them to Type C
> > connectors, similar to USB ports.
> >
> > Heikki Krogerus (1):
> >   thunderbolt: Link USB4 ports to their USB Type-C connectors
> >
> > Won Chung (1):
> >   misc/mei: Add NULL check to component match callback functions
>
> The Thunderbolt patch looks good to me. Do you want me to take the both
> patches through the Thunderbolt tree or they can go separately? I need
> an ack from the mei maintainer it goes through my tree.

Hi Mika,

I would prefer the two patches to go to the same tree since it can
cause a crash with only the second patch (tbt). Would that sound okay?

Hey Alexander, would you be the right person to ask for an ack on this?

Thanks,
Won