From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AFEC1ECE587 for ; Tue, 1 Oct 2019 13:09:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F71321906 for ; Tue, 1 Oct 2019 13:09:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726770AbfJANJK (ORCPT ); Tue, 1 Oct 2019 09:09:10 -0400 Received: from mga14.intel.com ([192.55.52.115]:30595 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725821AbfJANJK (ORCPT ); Tue, 1 Oct 2019 09:09:10 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Oct 2019 06:09:10 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,571,1559545200"; d="scan'208";a="205061262" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.157]) by fmsmga001.fm.intel.com with SMTP; 01 Oct 2019 06:09:06 -0700 Received: by lahna (sSMTP sendmail emulation); Tue, 01 Oct 2019 16:09:05 +0300 Date: Tue, 1 Oct 2019 16:09:05 +0300 From: Mika Westerberg To: Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, Andreas Noever , Michael Jamet , Yehezkel Bernat , Rajmohan Mani , Nicholas Johnson , Lukas Wunner , Alan Stern , Mario.Limonciello@dell.com, Anthony Wong , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 17/22] thunderbolt: Add initial support for USB4 Message-ID: <20191001130905.GO2714@lahna.fi.intel.com> References: <20191001113830.13028-1-mika.westerberg@linux.intel.com> <20191001113830.13028-18-mika.westerberg@linux.intel.com> <20191001124748.GH2954373@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191001124748.GH2954373@kroah.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Oct 01, 2019 at 02:47:48PM +0200, Greg Kroah-Hartman wrote: > > - Thunderbolt Controller driver. This driver is required if you > > - want to hotplug Thunderbolt devices on Apple hardware or on PCs > > - with Intel Falcon Ridge or newer. > > + USB4 (Thunderbolt) driver. USB4 is the public spec based on > > + Thunderbolt 3 protocol. This driver is required if you want to > > + hotplug Thunderbolt and USB4 compliant devices on Apple > > + hardware or on PCs with Intel Falcon Ridge or newer. > > Wait, did "old" thunderbolt just get re-branded as USB4? Not but the driver started supporting USB4 as well :) USB4 is pretty much public spec of Thunderbolt 3 but with some differences in register layouts (this is because Thunderbolt uses some vendor specific capabilities which are now moved to more "standard" places). > Because if I have an "old" laptop that needs Thunderbolt support, how am > I going to know it is now called USB4 instead? Well the Kconfig option tries to have both names there: tristate "USB4 (Thunderbolt) support" and then USB4 (Thunderbolt) driver. USB4 is the public spec based on Thunderbolt 3 protocol. This driver is required if you want to hotplug Thunderbolt and USB4 compliant devices on Apple hardware or on PCs with Intel Falcon Ridge or newer. and the Kconfig option is still CONFIG_THUNDERBOLT. I know this is confusing but I don't have better ideas how we can advertise both. I borrowed this "format" from firewire. > Shouldn't there just be a new USB4 option that only enables/builds the > USB4 stuff if selected? Why would I want all of this additional code on > my old system if it's not going to do anything at all? USB4 devices are backward compatible with Thunderbolt 3 so you should be able to plug in USB4 device to your old Thunderbolt 3 laptop for example. It goes the other way as well. Some things are optional but for example USB4 hubs must support also Thunderbolt 3. Does that clarify?