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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 CC495C433DB for ; Thu, 4 Feb 2021 04:08:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6602664F41 for ; Thu, 4 Feb 2021 04:08:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229996AbhBDEIg (ORCPT ); Wed, 3 Feb 2021 23:08:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229786AbhBDEIg (ORCPT ); Wed, 3 Feb 2021 23:08:36 -0500 Received: from mail-pf1-x42a.google.com (mail-pf1-x42a.google.com [IPv6:2607:f8b0:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3FCBC0613D6 for ; Wed, 3 Feb 2021 20:07:55 -0800 (PST) Received: by mail-pf1-x42a.google.com with SMTP id m6so1288927pfk.1 for ; Wed, 03 Feb 2021 20:07:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=fOA87upY96wx5CXAVS9O4APStVDrdyQiHwsnXM+mTec=; b=sa59R/OzxkpnEIbtqjhQL5jTExM8FKCANWqyFCslWMkMYwBSZWDj4d1mAcRw8R7xn7 isiwAAhKC31uEQSIjaYGr5EMoFAg+rIo/s0b8dQV82uqYwtZ8InKg9q8sjR7+6afEOb3 SqsGALoM3Pa3yE9c8TQNhE0fRilA8LEBFltrujA3xzmyFjdVtRY8QnHSnNl6gFfxJahm wXXE2KSG4t0F5IIqSf70vxO6dwQDb+jdGgmbmcwsB1sVQov05cu/znMNuqq6ZhxDop51 AZkb7laPpVi27NYfr8uhNjTea+XaDNUT4d3m7PDAzOwoZuZ6WCn0YTzl7GVFNvDtQKah Llrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=fOA87upY96wx5CXAVS9O4APStVDrdyQiHwsnXM+mTec=; b=JhwDnPabr4y5zA/B2Ul23AqG3WcXTCZL03tFkOAnebp0Yzu2zd5sLizHlqifBvF0Yu 0wkQeiso95vxGM+DZo9ezTMvmnL0umvXmkdgoj2+UwQEcIfOrVn8Q44PMGBMLU13KsgF YKBWq6Xy2i5ayYkrmvMkWNZBgJKzdTeUlhBhG96e4qQqeuLnRasbZgCH4kyvqCjIs+1P WYn+we+zaf8ELKl7IcUR5F5X7+/NMFsTU0wzq1xjsfrnSLQhylj6K8gebd3jChPZQOsz Jio7oZ+muYQmBKPTWhYQvWkX7apR8wNiEqWu03yl8kc/BwUugRA/yIsv1l9DAQ4WN0dD HWNg== X-Gm-Message-State: AOAM530aTzTcoaCn1Q3RtN9Kl6NoOPH12SLN0pbZt7ZU2zp1xZFwsS+F pXvsqlMMxOAmm2VzYYIA82LH X-Google-Smtp-Source: ABdhPJy467GxfvHn3Ve+OONVt2FbgC7gDKGno9kW/cY2dEIbXI24laqwCf54pVWRUEvz4zrvZuASrQ== X-Received: by 2002:a62:bd05:0:b029:1ab:6d2:5edf with SMTP id a5-20020a62bd050000b02901ab06d25edfmr6267487pff.32.1612411675035; Wed, 03 Feb 2021 20:07:55 -0800 (PST) Received: from thinkpad ([2409:4072:502:e1e4:2c42:3883:f540:5b9c]) by smtp.gmail.com with ESMTPSA id j3sm3435456pjs.50.2021.02.03.20.07.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Feb 2021 20:07:54 -0800 (PST) Date: Thu, 4 Feb 2021 09:37:46 +0530 From: Manivannan Sadhasivam To: Jakub Kicinski Cc: Loic Poulain , Greg KH , David Miller , linux-arm-msm , open list , Jeffrey Hugo , Bhaumik Bhatt , Network Development Subject: Re: [RESEND PATCH v18 0/3] userspace MHI client interface driver Message-ID: <20210204040746.GA8235@thinkpad> References: <20210201105549.GB108653@thinkpad> <20210201121322.GC108653@thinkpad> <20210202042208.GB840@work> <20210202201008.274209f9@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <835B2E08-7B84-4A02-B82F-445467D69083@linaro.org> <20210203100508.1082f73e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <20210203104028.62d41962@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210203104028.62d41962@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Wed, Feb 03, 2021 at 10:40:28AM -0800, Jakub Kicinski wrote: > On Wed, 3 Feb 2021 19:28:28 +0100 Loic Poulain wrote: > > On Wed, 3 Feb 2021 at 19:05, Jakub Kicinski wrote: > > > On Wed, 03 Feb 2021 09:45:06 +0530 Manivannan Sadhasivam wrote: > > > > The current patchset only supports QMI channel so I'd request you to > > > > review the chardev node created for it. The QMI chardev node created > > > > will be unique for the MHI bus and the number of nodes depends on the > > > > MHI controllers in the system (typically 1 but not limited). > > > > > > If you want to add a MHI QMI driver, please write a QMI-only driver. > > > This generic "userspace client interface" driver is a no go. Nobody will > > > have the time and attention to police what you throw in there later. > > > > Think it should be seen as filtered userspace access to MHI bus > > (filtered because not all channels are exposed), again it's not > > specific to MHI, any bus in Linux offers that (i2c, spi, usb, serial, > > etc...). It will not be specific to QMI, since we will also need it > > for MBIM (modem control path), AT commands, and GPS (NMEA frames), all > > these protocols are usually handled by userspace tools and not linked > > to any internal Linux framework, so it would be better not having a > > dedicated chardev for each of them. > > The more people argue for this backdoor interface the more distrustful > of it we'll become. Keep going at your own peril. Sorry, I do not want this to go towards rant... But I don't think this is anyway near a backdoor interface. There are userspace tools available to evaluate the chardev node and whatever this driver supports and going to support in the future is part of the Qualcomm modems. The fact that we can't add a separate driver for MHI QMI is due to the code duplication as the underlying interface is same it is just the channel which differs. And I got your point in doing everything in the chardev'ish way here. But we don't have any standard mechanism (QMI, MBIM, firmware/crash dump download). And lot of people argued that we are too far away from creating a WWAN subsystem. And the usecase we are dealing here is specific to Qualcomm. So IMO we should go ahead with the current interface this driver offers. Thanks, Mani