linux-kernel - Re: [PATCH 1/9] usb: typec: Add support for retimers

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Date:   Thu, 30 Jun 2022 13:18:33 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Prashant Malani <pmalani@...omium.org>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        chrome-platform@...ts.linux.dev, bleung@...omium.org,
        Daisuke Nojiri <dnojiri@...omium.org>,
        "Dustin L. Howett" <dustin@...ett.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Sebastian Reichel <sebastian.reichel@...labora.com>
Subject: Re: [PATCH 1/9] usb: typec: Add support for retimers

On Thu, Jun 30, 2022 at 11:17:59AM +0300, Heikki Krogerus wrote:
> On Wed, Jun 29, 2022 at 11:32:19PM +0000, Prashant Malani wrote:
> > Introduce a retimer device class and associated functions that register
> > and use retimer "switch" devices. These operate in a manner similar to
> > the "mode-switch" and help configure retimers that exist between the
> > Type-C connector and host controller(s).
> > 
> > Type C ports can be linked to retimers using firmware node device
> > references (again, in a manner similar to "mode-switch").
> > 
> > Signed-off-by: Prashant Malani <pmalani@...omium.org>
> 
> Cool! This looks really good to me.
> 
> I'll add Mika here, just to keep him in the loop. Thunderbolt/USB4 can
> control the same physical retimers over the SBU line. Right now there
> is no conflict, but I think we want to later be able to use these
> devices to upgrade the retimer firmware, and that is something that
> the Thunderbolt/USB4 already does. So let's keep an eye on this.
> 
> I wonder, would it make sense to later make the thunderbolt_retimer
> devices also part of the device class that's introduced here? I think
> that way it would be easier to later figure out which
> thunderbolt_retimer and which retimer_switch represent the same
> physical retimer. And perhaps it would also be more clear for the user
> space to have a single device class for the retimers?

I agree this makes sense.