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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 130B0CD5BAB for ; Sun, 24 May 2026 18:21:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ti+0QCXGT7ETl1POeyETi1M8HN2lZW4xpw/OVCjE8eQ=; b=GDHzqH5rHS1L9jASwshV45IskW 27JhiKMXUd2SAgfBg564cfQ6ccGAMK0FKImcQEnPuVPe1oWDwyhD2zgVhTgcj2G4O3qaGBW8PiwS0 dkINL2VAChWp7OyQaDy8bfU+Nf3mWcVa8y2/9RDtDY7K7xaBYesQZSuTtuRKHZ6dk6mEVup/yw8ko LxtMM0NwPPz73tfV9KkLoyrV4fnKt6tiD04Bn1zzH3kB2gVIjBsjuDKa5s+2tYcTnSU8dOE4PL2O0 e7KT+wjFUaBU2zmn2uhmT3Hx5Gbwq1RYVY/sotb0+Wadw1hbpjy/YUastBdtOM65bGBClub0MpBYi nu0K3WOQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRDRb-0000000FPfD-1FED; Sun, 24 May 2026 18:20:59 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRDRa-0000000FPf2-0ZDX for linux-arm-kernel@lists.infradead.org; Sun, 24 May 2026 18:20:58 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 32254601F4; Sun, 24 May 2026 18:20:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3D8C1F000E9; Sun, 24 May 2026 18:20:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779646856; bh=ti+0QCXGT7ETl1POeyETi1M8HN2lZW4xpw/OVCjE8eQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=amOuWBZRkpbbzWRXSo0gLh2BW8aM/+huZFF2HgwpnPIrHiaifu58+cgFfxhkF4Yu9 4tjk0xP50i8CFEvfYatq3JDxwCU7iykVppJ/J1PD5sD7WMqceQ0YtJhWw36nQTdFxF rEp77CXtuolc9w+Gcc+YkxFjC3WnAt0U9VWh5Y4QsOHBMryussGc2P09HAdmAuAM56 znOWGWHlv/Q9JcIRiqSdAUKHZFQUtaxuKOJLBjj4Q7YwRb4VYtWE8Seiu22Gqw0h2D HVMbttNmUIiRokX5YHhFZLOoU6u0/5xCymzbnz+Wg4HV6KEh/c1PGtP1UXD/dNuFnz OlRdFgjSuZykQ== Message-ID: <74eb56fb-546d-4b2c-9bbc-01a40937f5d3@kernel.org> Date: Sun, 24 May 2026 20:20:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] dt-bindings: connector: Add fsl,io-connector binding To: Frank Li Cc: "Chancel Liu (OSS)" , Chancel Liu , "robh@kernel.org" , "krzk+dt@kernel.org" , "conor+dt@kernel.org" , "s.hauer@pengutronix.de" , "festevam@gmail.com" , "mturquette@baylibre.com" , "sboyd@kernel.org" , "kernel@pengutronix.de" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "imx@lists.linux.dev" , "linux-arm-kernel@lists.infradead.org" , "linux-clk@vger.kernel.org" References: <20260509024846.2094049-1-chancel.liu@nxp.com> <20260509024846.2094049-3-chancel.liu@nxp.com> <20260515-resourceful-singing-roadrunner-ce25ec@quoll> <20260519-macho-degu-from-nibiru-960af2@quoll> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 20/05/2026 16:33, Frank Li wrote: > On Wed, May 20, 2026 at 09:08:42AM +0200, Krzysztof Kozlowski wrote: >> On 20/05/2026 07:02, Chancel Liu (OSS) wrote: >>>>>>>>> +description: >>>>>>>>> + The NXP I/O connector represents a physically present I/O >>>>>>>>> +connector on the >>>>>>>>> + base board. It acts as a nexus that exposes a constrained set >>>> of >>>>>>>>> +I/O >>>>>>>>> + resources, such as GPIOs, clocks, PWMs and interrupts, through >>>>>>>>> +fixed >>>>>>>>> + electrical wiring. All actual hardware providers reside on the >>>> base >>>>>> board. >>>>>>>>> + The connector node only defines index-based mappings to those >>>>>>>> providers. >>>>>>>>> + >>>>>>>>> +properties: >>>>>>>>> + compatible: >>>>>>>>> + const: fsl,io-connector >>>>>>>> >>>>>>>> Everything is IO. Everything is connector, so your compatible does >>>>>>>> not match requirements from writing bindings. >>>>>>>> >>>>>>> >>>>>>> Yes, this compatible is too generic. I will rename the compatible to >>>>>>> fsl,aud-io-connector. >>>>>> >>>>>> aud is not much better. Which boards have it? What's the pinout? >>>> What's >>>>>> standard? Is it described anywhere? If so, provide reference to >>>> spec/docs. >>>>>> >>>>> >>>>> This is not an industry standard electrical interface. This connector >>>> >>>> Then if you do not have standard, then you have board specific layouts >>>> thus you need board-specific compatibles. You can use fallbacks. Generic >>>> fallback could work, but both io-connector and aud-io-connector are just >>>> too generic. Every connector is "connector" and "io", thus absolutely >>>> anything can be "io-connector". "aud" improves it only a bit, thus >>>> honestly I would go with board specific fallback as well. >>>> >>> >>> How about board specific + common fallback compatible like this: >>> compatible: >>> items: >>> - enum: >>> - fsl,imx95-19x19-evk-aud-io-connector >>> - fsl,imx952-evk-aud-io-connector >>> - const: fsl,imx-aud-io-connector >>> Since the daughter board is named “IMX-AUD-IO” in publicly available >> >> I don't think it is named like that. >> >> git grep -i imx-aud-io >> >>> documentation, common compatible clearly indicates that this connector >>> is intended for that. >>> >>> Also, I want to talk about the topic of generic connector. It's a common >>> design that daughter board is connected to base board through a >>> connector. This connector more often acts as a nexus that exposes a >>> constrained subset of GPIO, clock, PWM and interrupt resources to the >>> daughter board. Can we document this kind of connector as a generic >>> binding? >> >> So this binding is the connector between carrier and some addon? Then >> you don't get a compatible for that at all, because it is not necessary, >> not useful and NEVER used. Do you see socket LGA "connector" bindings? No. > > Not exactly. Any connector connects a carrier board with an add-on board. > The key point here is that this connector type is reused across different > boards, even though it is not an industry-standard connector. Both the > signal definitions and the mechanical layout are defined. > > The same add-on boards can therefore be reused across different base boards > that use this type of connector. > > There are also GPIO mappings involved. For example, pin 1 on the connector > may represent reset-gpios, but it could be connected to GPIO0 on board A > and GPIO1 on board B. > > Without a connector definition layer, this would create an N × M > combination problem. The Nexus node discussion already covered this topic: > https://osseu2025.sched.com/event/25Vrw > > An LGA socket is a CPU socket, where the signals are completely transparent > to software, so it is not a good comparison. A PCIe M.2 Key-M/E connector > would be a more appropriate comparison. > So the terminology of daughter and carrier boards was confusing. If this is a hat, mezzanine or other addon, it's fine. I still insist on board specific compatibles - fallback and specific. Best regards, Krzysztof