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,URIBL_BLOCKED autolearn=unavailable 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 73FE7C04AB5 for ; Mon, 3 Jun 2019 14:50:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D20A26BA1 for ; Mon, 3 Jun 2019 14:50:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729145AbfFCOuj (ORCPT ); Mon, 3 Jun 2019 10:50:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34376 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727415AbfFCOui (ORCPT ); Mon, 3 Jun 2019 10:50:38 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0328830917AB; Mon, 3 Jun 2019 14:50:32 +0000 (UTC) Received: from ovpn-112-59.rdu2.redhat.com (ovpn-112-59.rdu2.redhat.com [10.10.112.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id CCFC72E053; Mon, 3 Jun 2019 14:50:25 +0000 (UTC) Message-ID: <99b9a24b229975689fb4686915190200606e8afc.camel@redhat.com> Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver From: Dan Williams To: Subash Abhinov Kasiviswanathan , Bjorn Andersson Cc: Alex Elder , Arnd Bergmann , 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: Mon, 03 Jun 2019 09:50:24 -0500 In-Reply-To: References: <20190531035348.7194-1-elder@linaro.org> <065c95a8-7b17-495d-f225-36c46faccdd7@linaro.org> <20190531233306.GB25597@minitux> 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 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Mon, 03 Jun 2019 14:50:38 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 2019-05-31 at 17:59 -0600, Subash Abhinov Kasiviswanathan wrote: > On 2019-05-31 17:33, Bjorn Andersson wrote: > > On Fri 31 May 13:47 PDT 2019, Alex Elder wrote: > > > > > On 5/31/19 2:19 PM, Arnd Bergmann wrote: > > > > On Fri, May 31, 2019 at 6:36 PM Alex Elder > > > > wrote: > > > > > On 5/31/19 9:58 AM, Dan Williams wrote: > > > > > > On Thu, 2019-05-30 at 22:53 -0500, Alex Elder wrote: > > > > > > > > > > > > My question from the Nov 2018 IPA rmnet driver still > > > > > > stands; how does > > > > > > this relate to net/ethernet/qualcomm/rmnet/ if at all? And > > > > > > if this is > > > > > > really just a netdev talking to the IPA itself and > > > > > > unrelated to > > > > > > net/ethernet/qualcomm/rmnet, let's call it "ipa%d" and stop > > > > > > cargo- > > > > > > culting rmnet around just because it happens to be a net > > > > > > driver for a > > > > > > QC SoC. > > > > > > > > > > First, the relationship between the IPA driver and the rmnet > > > > > driver > > > > > is that the IPA driver is assumed to sit between the rmnet > > > > > driver > > > > > and the hardware. > > > > > > > > Does this mean that IPA can only be used to back rmnet, and > > > > rmnet > > > > can only be used on top of IPA, or can or both of them be > > > > combined > > > > with another driver to talk to instead? > > > > > > No it does not mean that. > > > > > > As I understand it, one reason for the rmnet layer was to > > > abstract > > > the back end, which would allow using a modem, or using something > > > else (a LAN?), without exposing certain details of the hardware. > > > (Perhaps to support multiplexing, etc. without duplicating that > > > logic in two "back-end" drivers?) > > > > > > To be perfectly honest, at first I thought having IPA use rmnet > > > was a cargo cult thing like Dan suggested, because I didn't see > > > the benefit. I now see why one would use that pass-through layer > > > to handle the QMAP features. > > > > > > But back to your question. The other thing is that I see no > > > reason the IPA couldn't present a "normal" (non QMAP) interface > > > for a modem. It's something I'd really like to be able to do, > > > but I can't do it without having the modem firmware change its > > > configuration for these endpoints. My access to the people who > > > implement the modem firmware has been very limited (something > > > I hope to improve), and unless and until I can get corresponding > > > changes on the modem side to implement connections that don't > > > use QMAP, I can't implement such a thing. > > > > > > > But any such changes would either be years into the future or for > > specific devices and as such not applicable to any/most of devices > > on > > the market now or in the coming years. > > > > > > But as Arnd points out, if the software split between IPA and rmnet > > is > > suboptimal your are encouraged to fix that. > > > > Regards, > > Bjorn > > The split rmnet design was chosen because we could place rmnet > over any transport - IPA, PCIe (https://lkml.org/lkml/2018/4/26/1159) > or USB. Yeah, that's what I was looking for clarification on :) Clearly since rmnet can have many transports it should be able to be used by different HW drivers, be that qmi_wwan, IPA, and maybe even rmnet_smd.c? > rmnet registers a rx handler, so the rmnet packet processing itself > happens in the same softirq when packets are queued to network stack > by IPA. This directly relates to the discussion about a WWAN subsystem that Johannes Berg started a couple weeks ago. IPA appears to create a netdev of its own. Is that netdev usable immediately, or does one need to create an rmnet device on top to access the default PDN? Thanks, Dan