From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9E038315D31 for ; Tue, 16 Sep 2025 12:22:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758025348; cv=none; b=b4mWa09rQJYsFes/D/i/LklEzJupOiRuRiECZ32OAHSiG34xnwMF1xNwuTeMVtlQEx3/OCR7n4R2Cxb+BZJ1BL93qns0h15enDO+LiEU4ISfQir10Dpx+Kw4rf7WW8EIqmFBJF0dbNMLBnbJzqgfBzdK6UPw5AUAs/OJlyCGJB8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758025348; c=relaxed/simple; bh=fqM/JGxWXDvWSyz6fzJ8EaAgZz1wCn9ix0KOBZDkuEs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DaogS/GF0BFtVuAoMHpnjXCK9IbPSIfQQXQ8qfldyHNV1CuqcFc//FJfoWg6r8eOP2a5bWs8L4Wk53pwg/seAxquJ1Sj6oqeKRYr/EPP/qTYnScWQxJOc2bsobNjXFmlMRZxpLPbUoJ0VtPjp5T4jdRR4DSPD+LkxEP20xR+9A8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=beagleboard.org; spf=fail smtp.mailfrom=beagleboard.org; dkim=pass (2048-bit key) header.d=beagleboard-org.20230601.gappssmtp.com header.i=@beagleboard-org.20230601.gappssmtp.com header.b=z7NfGuaM; arc=none smtp.client-ip=209.85.214.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=beagleboard.org Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=beagleboard.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=beagleboard-org.20230601.gappssmtp.com header.i=@beagleboard-org.20230601.gappssmtp.com header.b="z7NfGuaM" Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-2570bf6058aso70193625ad.0 for ; Tue, 16 Sep 2025 05:22:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=beagleboard-org.20230601.gappssmtp.com; s=20230601; t=1758025346; x=1758630146; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=nLRhawfUOnzg917Vpj9Yo7NT/ncmZFWuu+3t8quChCY=; b=z7NfGuaMEujffC2agRNlu32/G1h0DuHPIXz/M39LNU4eP9bKAphTXYaMYqTcYjWPIa pi4FZsZpYG93Yfgk0gaN1gK4MFJ4Hmx55caMZiGpfbkIz4mTvDvZcpAk3B7Fj4KaRDZU UUFu27h/n1yjfh+7jOHebYPR7z6GZYGBz3iwpYkBGsAMTizyRZOkmqYVTQKni/nL38G2 vv8+EYGgWbTQYiFLlDalG5Z8Q9lMWT97aHqZpZ+9GDxEUOzOGAY3YokiXnJMbumdVOll 9gnBKk7PYJx+Mq6ipAg+05+WGXoDbyYQpbj48x7+h9drV5fpCVYI8CQwM246RW0dNfPK Mvww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758025346; x=1758630146; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=nLRhawfUOnzg917Vpj9Yo7NT/ncmZFWuu+3t8quChCY=; b=C027fEw2YcMnbDDXNGkDTqBBWH30m3YRNzX6bD8qYEKRFWapICkNtRoivGIEYRMIZz yS5jHvBuRFOK0Lc5g3j7sznHLuBFcGcPeejFHAc1kBdL9ZAaYyPRswGh97MgPW7MWksQ xq/omr3/dlM0IT3HujfXm0K8ehYAKfHvzKp/oPHL491edaL8W2rtJlJGTLrTVDZuxFtT HFHIf+2D1pQMYvdSf7xtGktJNJ4JjyM49wCSb1R9SuhuYjlPThut3PuW33V8noW2ak2D aJWw7ncuXMq6HCKrKEVrzddPIAou1GjOlXk7BJBjnwKLWU7kmbfbooOQZCjYU8qG7jkW tnLQ== X-Forwarded-Encrypted: i=1; AJvYcCUJOPl3OeM3HDOMRe/4RSz+uBnqjtOTGZGltArpqyp3/zdVJvqHEuPIeP3545mW/idqaQevTelbprboXOo=@vger.kernel.org X-Gm-Message-State: AOJu0YyX687t5Zao0iesGp30LDhveSnL3igmxA5hRjjlJD9Ut8US07Ao eYDlGN10IpgJ9WmD3ryS/wwSvlJhdjPyQrV3aGSMibGqrNEwUTrerTQnTvsr79IPgQ== X-Gm-Gg: ASbGncvXuNsPQwZqW1JhQ0Mzo9unhs+V7B/kvj8eqm3haNd9/2NuhDchuPr+o+rZXgy myifxoOiaYCqP5Vrzs9xgZEIfHwfDGHgPG2ohxyNSVpjRmfA9WWQDZ1wuVtlRPHJ2vTC9YHsjcE halKTgQNOdMKc68Y19VdxdBlG6TW1uEoncCZfqTyf2JTzPzp2dznfzWEbWZwbXJK6qweJw1klpn qU/WRy7JXmrTFqhUqqN4jfnUHWIUJLSMx3tchbpri3OhKD13hi+1ue0XmWUs3T0OchJu1zAY+vL un53E4+3Qz83Z8nSw/14NVqSzMiY4c/A+PU4fo4+PsZvdVWWpSci1jH54rFqpW96GthhHfHHDt6 a90ySBK60X1w24h2ukAfLqLRNzactGE4AJFx/tAasWQpfRgNL7ECe7YtWuEU+GqPYhlNuOGRZIq 4J0/S7WkFz+2U= X-Google-Smtp-Source: AGHT+IHmBwkxP+Zhpk5HnX/FJ08tuJ9zeLX2LjBddCIb0Zkm2NtUoGbkRB7285Cr8PepXjQeRcICXA== X-Received: by 2002:a17:903:3d05:b0:267:f131:d657 with SMTP id d9443c01a7336-267f131d9a4mr5560315ad.33.1758025345718; Tue, 16 Sep 2025 05:22:25 -0700 (PDT) Received: from ?IPV6:2401:4900:1f3f:4017:94e1:4956:54cb:7de7? ([2401:4900:1f3f:4017:94e1:4956:54cb:7de7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2656a9caf7dsm66844215ad.133.2025.09.16.05.22.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 Sep 2025 05:22:25 -0700 (PDT) Message-ID: <397483db-91de-4ff2-82e3-52ae785bc343@beagleboard.org> Date: Tue, 16 Sep 2025 17:52:18 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Device tree representation of (hotplug) connectors: discussion at ELCE To: Geert Uytterhoeven , Herve Codina Cc: David Gibson , Luca Ceresoli , Krzysztof Kozlowski , devicetree@vger.kernel.org, Rob Herring , Jason Kridner , Krzysztof Kozlowski , Conor Dooley , devicetree-compiler@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Petazzoni , Andrew Davis , Wolfram Sang References: <20250902105710.00512c6d@booty> <337281a8-77f9-4158-beef-ae0eda5000e4@beagleboard.org> <20250908145155.4f130aec@bootlin.com> <20250909114126.219c57b8@bootlin.com> <20250911104828.48ef2c0e@bootlin.com> <20250916084631.77127e29@bootlin.com> Content-Language: en-US From: Ayush Singh In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 9/16/25 15:44, Geert Uytterhoeven wrote: > Hi Hervé, > > On Tue, 16 Sept 2025 at 08:46, Herve Codina wrote: >> On Mon, 15 Sep 2025 14:51:41 +1000 >> David Gibson wrote: >>> On Thu, Sep 11, 2025 at 10:48:28AM +0200, Herve Codina wrote: >>>> From the addon board point of view, the only think we can >>>> say is "me, as an addon board, I need a connector of type 'foo' and a >>>> connector of type 'bar'". >>> Agreed. >>> >>>> Also, at base board level, statically defined in the DT >>>> connA is described (type 'foo'), connB and connC are >>>> described (type 'bar'). >>>> >>>> The choice to map connA to the type 'foo' connector expected by the addon >>>> and the choice to map connB or connC to the type 'bar' connector expected by >>>> the addon can only be done at runtime and probably with the help of a driver >>>> that have the knowledge of the 3 connectors. >>> Agreed. >>> >>>> I have the feeling that the choice of physical connectors to which the addon >>>> board is connected to is a human choice when the board is connected. >>> Yes. Although if the addons have an EEPROM, or some other sort of ID >>> register, it may be possible for some connector drivers to probe this. >> Right, I think we agree that a driver is needed to help in the mapping at >> least when multiple connectors are involved. > I agree you need a driver to read an ID EEPROM. > But why would you need a driver if no ID EEPROM is involved? > If the connector types on base board and add-on match, it should work. > > Gr{oetje,eeting}s, > > Geert > How would a connector be disabled in such a setup? I guess maybe status property can be used while applying overlay to check if the connector is enabled. But maybe that goes outside the scope of fdtoverlay? Also, I would assume that most such connectors would want to provide some kind of configfs based API to add/remove addon boards. Best Regards, Ayush Singh