From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-03.galae.net (smtpout-03.galae.net [185.246.85.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A2917327A1B; Tue, 23 Sep 2025 13:37:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.85.4 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758634631; cv=none; b=WYXfwCJGteQ+lalV+qduVR3k65xjQohpzKTlVokR0KZOAdkDP9m+tLKpxdkiU4Vbr8umyfe3uBh0KykSri8AyB0dVp4Wgp1OP8G2eswR8nTwwKmYhvuiaEh4AyYpYJOhB2DPVmusZmE8wD8q66RMxz0L0e/JpYQHObxOGxblmJc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758634631; c=relaxed/simple; bh=IjG04YAsgqRFw7Eb4bkKvESHmFuVAEmEfIf7vfwOwb4=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=lNVUwmduxoNAzqpSqloQQ4r8uNNJSQWR1sv3r4rw9VcasbKrZOmUq9E+rwu751Ljp4SoH3mwiXVCX9ChJrdcJOPLfjzrkS0FUATZSpcS8Nd8/lu7xg2U8LFfu+IESXY3fMMfMtmx2t8z5XPBr8cAgaVsf3/1QUD5EoENvB/2ZVI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=DVpWf27E; arc=none smtp.client-ip=185.246.85.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="DVpWf27E" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-03.galae.net (Postfix) with ESMTPS id ACCA44E40CAD; Tue, 23 Sep 2025 13:37:06 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 8088C60690; Tue, 23 Sep 2025 13:37:06 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 901BD102F1950; Tue, 23 Sep 2025 15:36:47 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1758634625; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=KBPR5buXz86hknin/D1hAnT/+VJp1Du2pRilGmtvOAw=; b=DVpWf27EyfK2+Gd/sf4BJ5J0yv2Sl36D5fnkCVNFBZOPRkyCLlgY8T+tPxjzW0F5YXpUtf 0MpB8DZpOdzDeZ6108lfaKxgN7URcpdc9jNQ9EMVcuAwdFXi7+J6RelhVyIeZ2xgB/cGnf GBZet49ZmXyY4pV55yX0u3ta+loar2Zfq4chLMR2VEnaAn1X+WWdimwOJ/5BUkRc2Hfxlj t75DnNVvgCIXP91f+q52pTUY4itQz9RQ7XJIKAZqL1MiC0N71NUTC1MpBWkfFr52Dv6UvX drfeGAk7+xVfgs7+TNGrJVN8084+YjjJabDjkdZZ3KLOz51RW/D57fI/cdcp9Q== Date: Tue, 23 Sep 2025 15:36:46 +0200 From: Herve Codina To: Geert Uytterhoeven Cc: David Gibson , Ayush Singh , Krzysztof Kozlowski , Rob Herring , Andrew Davis , Wolfram Sang , Luca Ceresoli , devicetree@vger.kernel.org, Jason Kridner , Krzysztof Kozlowski , Conor Dooley , devicetree-compiler@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Petazzoni Subject: Re: Device tree representation of (hotplug) connectors: discussion at ELCE Message-ID: <20250923153646.754e86f8@bootlin.com> In-Reply-To: References: <20250909114126.219c57b8@bootlin.com> <20250911104828.48ef2c0e@bootlin.com> <20250916084631.77127e29@bootlin.com> <20250918094409.0d5f92ec@bootlin.com> <20250923114849.2385736d@bootlin.com> Organization: Bootlin X-Mailer: Claws Mail 4.3.1 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 On Tue, 23 Sep 2025 12:29:27 +0200 Geert Uytterhoeven wrote: > Hi Hervé, > > On Tue, 23 Sept 2025 at 11:49, Herve Codina wrote: > > On Tue, 23 Sep 2025 18:09:13 +1000 > > David Gibson wrote: > > > Ah, right. To be clear: we absolutely don't want multiple addons > > > altering the same nodes. But I think we could do that in ways other > > > than putting everything under a connector. This is exactly why I > > > think we should think this through as an end-to-end problem, rather > > > trying to do it as a tweak to the existing (crap) overlay system. > > > > > > So, if we're thinking of this as an entirely new way of updating the > > > base dt - not "an overlay" - we can decide on the rules to ensure that > > > addition and removal is sane. Two obvious ones I think we should > > > definitely have are: > > > > > > a) Addons can only add completely new nodes, never modify existing > > > ones. This means that whatever addons are present at runtime, > > > every node has a single well defined owner (either base board or > > > addon). > > > > In this rule I suppose that "never modify existing ones" should be understood > > as "never modify, add or remove properties in existing ones". Because, of course > > adding a full node in a existing one is allowed (rule b). > > What if the add-on board contains a provider for the base board. > E.g. the connector has a clock input, fed by an optional clock generator > on the add-on board. Hooking that into the system requires modifying > a clocks property in the base board, cfr. [1]. > Or is there some other solution? > > I was also wondering about endpoints, as they have two sides: one on > the base board, and one on the add-on board. But it seems that typically > both ends are added by the extension, so these fall under rule b. > > Thanks! > > [1] https://elixir.bootlin.com/linux/v6.16/source/arch/arm64/boot/dts/renesas/white-hawk-ard-audio-da7212.dtso#L165 > Hi Geert, Addon DT we talk about is not a way to fine tune base board devices. For the clock, you need a clock driver which is able to support clock hot-plugging. Same for endpoint, the remote endpoint part should support hot-plugging. I don't think that addon DT should support what is done in the dtso you pointed out. Best regards, Hervé