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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8A03C28D13 for ; Mon, 22 Aug 2022 13:29:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235110AbiHVN3z (ORCPT ); Mon, 22 Aug 2022 09:29:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235190AbiHVN3k (ORCPT ); Mon, 22 Aug 2022 09:29:40 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E1D7518346; Mon, 22 Aug 2022 06:29:39 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4B50761196; Mon, 22 Aug 2022 13:29:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D7E7C433C1; Mon, 22 Aug 2022 13:29:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661174978; bh=tKR+1ncaLktuwBqOq+cs01Cvto2mRKf0wx5WnwSpD0c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LTkh9d2Haa525kwq2grlzk2TfJzupWlmdIDQ5qo0V4w55EsXMCH6v1DJh2tvLXpfu DrZ7mhtp3qKmb7fNWOImHLVlYbOQdRn88AvwmFxXXov+Y+Bv007ApBHm64gHBnHBZr s2NReW++3jE2tMLkvDU/VdpAQO1j8Q8pySCO8tns= Date: Mon, 22 Aug 2022 15:29:35 +0200 From: Greg KH To: "Gupta, Nipun" Cc: "robh+dt@kernel.org" , "krzysztof.kozlowski+dt@linaro.org" , "rafael@kernel.org" , "eric.auger@redhat.com" , "alex.williamson@redhat.com" , "cohuck@redhat.com" , "Gupta, Puneet (DCG-ENG)" , "song.bao.hua@hisilicon.com" , "mchehab+huawei@kernel.org" , "maz@kernel.org" , "f.fainelli@gmail.com" , "jeffrey.l.hugo@gmail.com" , "saravanak@google.com" , "Michael.Srba@seznam.cz" , "mani@kernel.org" , "yishaih@nvidia.com" , "jgg@ziepe.ca" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , "kvm@vger.kernel.org" , "okaya@kernel.org" , "Anand, Harpreet" , "Agarwal, Nikhil" , "Simek, Michal" , "git (AMD-Xilinx)" , "jgg@nvidia.com" , Robin Murphy Subject: Re: [RFC PATCH v2 2/6] bus/cdx: add the cdx bus driver Message-ID: References: <20220803122655.100254-1-nipun.gupta@amd.com> <20220817150542.483291-1-nipun.gupta@amd.com> <20220817150542.483291-3-nipun.gupta@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 22, 2022 at 01:21:47PM +0000, Gupta, Nipun wrote: > [AMD Official Use Only - General] > > > > > -----Original Message----- > > From: Greg KH > > Sent: Wednesday, August 17, 2022 9:03 PM > > To: Gupta, Nipun > > Cc: robh+dt@kernel.org; krzysztof.kozlowski+dt@linaro.org; rafael@kernel.org; > > eric.auger@redhat.com; alex.williamson@redhat.com; cohuck@redhat.com; > > Gupta, Puneet (DCG-ENG) ; > > song.bao.hua@hisilicon.com; mchehab+huawei@kernel.org; maz@kernel.org; > > f.fainelli@gmail.com; jeffrey.l.hugo@gmail.com; saravanak@google.com; > > Michael.Srba@seznam.cz; mani@kernel.org; yishaih@nvidia.com; > > jgg@ziepe.ca; linux-kernel@vger.kernel.org; devicetree@vger.kernel.org; > > kvm@vger.kernel.org; okaya@kernel.org; Anand, Harpreet > > ; Agarwal, Nikhil ; > > Simek, Michal ; git (AMD-Xilinx) > > Subject: Re: [RFC PATCH v2 2/6] bus/cdx: add the cdx bus driver > > > > [CAUTION: External Email] > > > > On Wed, Aug 17, 2022 at 08:35:38PM +0530, Nipun Gupta wrote: > > > CDX bus driver manages the scanning and populating FPGA > > > based devices present on the CDX bus. > > > > > > The bus driver sets up the basic infrastructure and fetches > > > the device related information from the firmware. These > > > devices are registered as platform devices. > > > > Ick, why? These aren't platform devices, they are CDX devices. Make > > them real devices here, don't abuse the platform device interface for > > things that are not actually on the platform bus. > > CDX is a virtual bus (FW based) which discovers FPGA based platform > devices based on communication with FW. virtual busses are fine to have as a real bus in the kernel, no problem there. > These devices are essentially platform devices as these are memory mapped > on system bus, but having a property that they are dynamically discovered > via FW and are rescannable. If they are dynamically discoverable and rescannable, then great, it's a bus in the kernel and NOT a platform device. > I think your point is correct in the sense that CDX bus is not an actual bus, > but a FW based mechanism to discover FPGA based platform devices. > > Can you kindly suggest us if we should have the CDX platform device scanning > code as a CDX bus in "drivers/bus/" folder OR have it in "drivers/fpga/" or > "drivers/platform/" or which other suitable location? drivers/cdx/ ? thanks, greg k-h