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=-0.8 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 BA6C0C4321A for ; Tue, 11 Jun 2019 08:13:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9549420652 for ; Tue, 11 Jun 2019 08:13:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404689AbfFKINE (ORCPT ); Tue, 11 Jun 2019 04:13:04 -0400 Received: from s3.sipsolutions.net ([144.76.43.62]:41602 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404512AbfFKIND (ORCPT ); Tue, 11 Jun 2019 04:13:03 -0400 Received: by sipsolutions.net with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1habtd-00061s-L7; Tue, 11 Jun 2019 10:12:45 +0200 Message-ID: Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver From: Johannes Berg To: elder@linaro.org Cc: abhishek.esse@gmail.com, arnd@arndb.de, benchan@google.com, bjorn.andersson@linaro.org, cpratapa@codeaurora.org, davem@davemloft.net, dcbw@redhat.com, devicetree@vger.kernel.org, ejcaruso@google.com, evgreen@chromium.org, ilias.apalodimas@linaro.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-soc@vger.kernel.org, netdev@vger.kernel.org, subashab@codeaurora.org, syadagir@codeaurora.org Date: Tue, 11 Jun 2019 10:12:43 +0200 In-Reply-To: <380a6185-7ad1-6be0-060b-e6e5d4126917@linaro.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-2.fc28) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Alex, all, > > 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. > > I looked at Johannes' message and the follow-on discussion. Thanks :-) Sorry also, Dan had pointed me to this thread and the discussion, but I was travelling last week and not very reachable. > As I've > made clear before, my work on this has been focused on the IPA transport, > and some of this higher-level LTE architecture is new to me. But it > seems pretty clear that an abstracted WWAN subsystem is a good plan, > because these devices represent a superset of what a "normal" netdev > implements. I'm not sure I'd actually call it a superset. By themselves, these netdevs are actually completely useless to the network stack, AFAICT. Therefore, the overlap with netdevs you can really use with the network stack is pretty small? > HOWEVER I disagree with your suggestion that the IPA code should > not be committed until after that is all sorted out. In part it's > for selfish reasons, but I think there are legitimate reasons to > commit IPA now *knowing* that it will need to be adapted to fit > into the generic model that gets defined and developed. Here > are some reasons why. I can't really argue with those, though I would point out that the converse also holds - if we commit to this now, then we will have to actually keep the API offered by IPA/rmnet today, so we cannot actually remove the netdev again, even if we do migrate it to offer support for a WWAN framework in the future. > Second, the IPA code has been out for review recently, and has been > the subject of some detailed discussion in the past few weeks. Arnd > especially has invested considerable time in review and discussion. > Delaying things until after a better generic model is settled on > (which I'm guessing might be on the order of months) I dunno if it really has to be months. I think we can cobble something together relatively quickly that addresses the needs of IPA more specifically, and then extend later? But OTOH it may make sense to take a more paced approach and think about the details more carefully than we have over in the other thread so far. > Third, having the code upstream actually means the actual requirements > for rmnet-over-IPA are clear and explicit. This might not be a huge > deal, but I think it's better to devise a generic WWAN scheme that > can refer to actual code than to do so with assumptions about what > will work with rmnet (and others). As far as I know, the upstream > rmnet has no other upstream back end; IPA will make it "real." Is that really true? I had previously been told that rmnet actually does have use with a few existing drivers. If true though, then I think this would be the killer argument *in favour* of *not* merging this - because that would mean we *don't* have to actually keep the rmnet API around for all foreseeable future. > I support the idea of developing a generic WWAN framework, and I > can assure you I'll be involved enough to perhaps be one of the > first to implement a new generic scheme. Thanks! johannes