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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 4B8EFC282CE for ; Tue, 4 Jun 2019 21:29:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F666207E0 for ; Tue, 4 Jun 2019 21:29:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726305AbfFDV3d (ORCPT ); Tue, 4 Jun 2019 17:29:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59564 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726033AbfFDV3d (ORCPT ); Tue, 4 Jun 2019 17:29:33 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AC5872F8BEA; Tue, 4 Jun 2019 21:29:32 +0000 (UTC) Received: from ovpn-112-67.rdu2.redhat.com (ovpn-112-67.rdu2.redhat.com [10.10.112.67]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5271C5C207; Tue, 4 Jun 2019 21:29:27 +0000 (UTC) Message-ID: <0264d7f9a35430201a89c068bb13c84c622af11a.camel@redhat.com> Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver From: Dan Williams To: Arnd Bergmann Cc: Alex Elder , Subash Abhinov Kasiviswanathan , Bjorn Andersson , David Miller , Ilias Apalodimas , evgreen@chromium.org, Ben Chan , Eric Caruso , cpratapa@codeaurora.org, syadagir@codeaurora.org, abhishek.esse@gmail.com, Networking , DTML , Linux Kernel Mailing List , linux-soc@vger.kernel.org, Linux ARM , linux-arm-msm@vger.kernel.org Date: Tue, 04 Jun 2019 16:29:26 -0500 In-Reply-To: References: <20190531035348.7194-1-elder@linaro.org> <065c95a8-7b17-495d-f225-36c46faccdd7@linaro.org> <20190531233306.GB25597@minitux> <040ce9cc-7173-d10a-a82c-5186d2fcd737@linaro.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 04 Jun 2019 21:29:33 +0000 (UTC) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Tue, 2019-06-04 at 22:04 +0200, Arnd Bergmann wrote: > On Tue, Jun 4, 2019 at 5:18 PM Dan Williams wrote: > > On Tue, 2019-06-04 at 10:13 +0200, Arnd Bergmann wrote: > > > Can you describe what kind of multiplexing is actually going on? > > > I'm still unclear about what we actually use multiple logical > > > interfaces for here, and how they relate to one another. > > > > Each logical interface represents a different "connection" (PDP/EPS > > context) to the provider network with a distinct IP address and > > QoS. > > VLANs may be a suitable analogy but here they are L3+QoS. > > > > In realistic example the main interface (say rmnet0) would be used > > for > > web browsing and have best-effort QoS. A second interface (say > > rmnet1) > > would be used for VOIP and have certain QoS guarantees from both > > the > > modem and the network itself. > > > > QMAP can also aggregate frames for a given channel > > (connection/EPS/PDP > > context/rmnet interface/etc) to better support LTE speeds. > > Thanks, that's a very helpful explanation! > > Is it correct to say then that the concept of having those separate > connections would be required for any proper LTE modem > implementation, > but the QMAP protocol (and based on that, the rmnet implementation) > is Qualcomm specific and shared only among several generations of > modems from that one vendor? Exactly correct. This is what Johannes is discussing in his "cellular modem APIs - take 2" thread about how this should all be organized at the driver level and I think we should figure that out before we commit to IPA-with-a-useless-netdev that requires rmnets to be created on top. That may end up being the solution but let's have that discussion. > > You mentioned the need to have a common user space interface > for configuration, and if the above is true, I agree that we should > try > to achieve that, either by ensuring rmnet is generic enough to > cover other vendors (and non-QMAP clients), or by creating a > new user level interface that IPA/rmnet can be adapted to. I would not suggest making rmnet generic; it's pretty QMAP specific (but QMAP is spoken by many many modems both SoC, USB stick, and PCIe minicard). Instead, I think what Johannes is discussing is a better approach. A kernel WWAN framework with consistent user API that rmnet/IPA/qmi_wwan/MBIM/QMI/serial/Sierra can all implement. That wouldn't affect the core packet processing of IPA/rmnet but instead: 1) when/how an rmnet device actually gets created on top of the IPA (or qmi_wwan) device AND (one of these two) a) whether IPA creates a netdev on probe OR b) whether there is some "WWAN device" kernel object which userspace interacts with create rmnet channels on top of IPA Dan