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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 BA51CC3526D for ; Fri, 18 Dec 2020 21:18:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9661A23B97 for ; Fri, 18 Dec 2020 21:18:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727381AbgLRVRo (ORCPT ); Fri, 18 Dec 2020 16:17:44 -0500 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:47981 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725843AbgLRVRo (ORCPT ); Fri, 18 Dec 2020 16:17:44 -0500 X-Originating-IP: 86.202.109.140 Received: from localhost (lfbn-lyo-1-13-140.w86-202.abo.wanadoo.fr [86.202.109.140]) (Authenticated sender: alexandre.belloni@bootlin.com) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id EF20A60003; Fri, 18 Dec 2020 21:16:58 +0000 (UTC) Date: Fri, 18 Dec 2020 22:16:58 +0100 From: Alexandre Belloni To: Jason Gunthorpe Cc: Mark Brown , Greg KH , Dan Williams , Pierre-Louis Bossart , alsa-devel@alsa-project.org, Kiran Patil , linux-rdma , Shiraz Saleem , Martin Habets , Liam Girdwood , Ranjani Sridharan , Fred Oh , Dave Ertman , Jakub Kicinski , Netdev , Leon Romanovsky , David Miller , Linux Kernel Mailing List , Parav Pandit , lee.jones@linaro.org Subject: Re: [resend/standalone PATCH v4] Add auxiliary bus support Message-ID: <20201218211658.GH3143569@piout.net> References: <20201217211937.GA3177478@piout.net> <20201218131709.GA5333@sirena.org.uk> <20201218140854.GW552508@nvidia.com> <20201218155204.GC5333@sirena.org.uk> <20201218162817.GX552508@nvidia.com> <20201218180310.GD5333@sirena.org.uk> <20201218184150.GY552508@nvidia.com> <20201218203211.GE5333@sirena.org.uk> <20201218205856.GZ552508@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201218205856.GZ552508@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/12/2020 16:58:56-0400, Jason Gunthorpe wrote: > On Fri, Dec 18, 2020 at 08:32:11PM +0000, Mark Brown wrote: > > > > So, I strongly suspect, MFD should create mfd devices on a MFD bus > > > type. > > > > Historically people did try to create custom bus types, as I have > > pointed out before there was then pushback that these were duplicating > > the platform bus so everything uses platform bus. > > Yes, I vaugely remember.. > > I don't know what to say, it seems Greg doesn't share this view of > platform devices as a universal device. > > Reading between the lines, I suppose things would have been happier > with some kind of inheritance scheme where platform device remained as > only instantiated directly in board files, while drivers could bind to > OF/DT/ACPI/FPGA/etc device instantiations with minimal duplication & > boilerplate. > > And maybe that is exactly what we have today with platform devices, > though the name is now unfortunate. > > > I can't tell the difference between what it's doing and what SOF is > > doing, the code I've seen is just looking at the system it's running > > on and registering a fixed set of client devices. It looks slightly > > different because it's registering a device at a time with some wrapper > > functions involved but that's what the code actually does. > > SOF's aux bus usage in general seems weird to me, but if you think > it fits the mfd scheme of primarily describing HW to partition vs > describing a SW API then maybe it should use mfd. > > The only problem with mfd as far as SOF is concerned was Greg was not > happy when he saw PCI stuff in the MFD subsystem. > But then again, what about non-enumerable devices on the PCI device? I feel this would exactly fit MFD. This is a collection of IPs that exist as standalone but in this case are grouped in a single device. Note that I then have another issue because the kernel doesn't support irq controllers on PCI and this is exactly what my SoC has. But for now, I can just duplicate the irqchip driver in the MFD driver. > This whole thing started when Intel first proposed to directly create > platform_device's in their ethernet driver and Greg had a quite strong > NAK to that. Let me point to drivers/net/ethernet/cadence/macb_pci.c which is a fairly recent example. It does exactly that and I'm not sure you could do it otherwise while still not having to duplicate most of macb_probe. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com