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

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Date:   Thu, 21 Apr 2022 09:00:31 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Won Chung <wonchung@...gle.com>
Cc:     Alexander Usyskin <alexander.usyskin@...el.com>,
        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

Hi,

On Wed, Apr 20, 2022 at 09:39:25AM -0700, Won Chung wrote:
> 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?

Sounds good to me.