Re: [PATCH 0/3] Introduce Thunderbolt/USB4 <-> USB Type-C port mapping

Greg KH
2025-04-15T12:22:13Z

On Tue, Apr 15, 2025 at 12:32:11PM +0300, Heikki Krogerus wrote:
> Hi Greg,
>
> On Mon, Apr 14, 2025 at 09:03:42PM +0200, Greg KH wrote:
> > On Mon, Apr 14, 2025 at 07:55:51PM +0200, Alan Borzeszkowski wrote:
> > > Hello everyone,
> > >
> > > This patch series introduces the creation of symlinks between
> > > Thunderbolt/USB4 ports and their corresponding USB Type-C ports. The
> > > primary goal is to provide users with clear visibility into which USB4
> > > port is connected via a specific Type-C port. This provides the same
> > > functionality that is already present in Chromebooks.
> >
> > "mapping" in what way? sysfs links? If so, care to add
> > Documentation/ABI/ updates?
>
> It is already there:
> https://docs.kernel.org/admin-guide/abi-testing.html#abi-sys-bus-thunderbolt-devices-usb4-portx-connector
>
> The link is already created on Cromebooks like Alan explained, because
> there each USB4/TBT port has a device node in the ACPI tables with the
> appropriate _PLD (Physical Location of Device), but on systems
> targeted primarily for Windows, that is not the case. There ports do
> not have device nodes, so we can't make the link based on _PLD.
>
> This series makes that same link by taking advantage of the
> "usb4-host-interface" _DSD device property [1] that we always have on
> those Windows platforms. That same device property that we also use in
> drivers/usb/code/usb-acpi.c, and probable some other places too.
>
> [1] https://www.usb.org/sites/default/files/D1T2-2%20-%20USB4%20on%20Windows.pdf

Thanks for the information, sorry I had missed that it was already
there.

greg k-h