From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 66AC42EFD99; Wed, 3 Dec 2025 11:08:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764760115; cv=none; b=DxnxRBhM5s9JvNtLARZ//vkMwIUQGWLU+xgDB0OdiMRRjEqCfwQRcwa5l4hfHentiYYr69bNZ+l4SMt5XrzC9UZP9InPfuTxJHis0t0oiP87aUf0Z7Hy74VfUQJYGjefszrvw+jEk84DyaYinsix3l5HhGr9C2Ks3sVbsxTD/tg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764760115; c=relaxed/simple; bh=t3W10qsRJTd3xYWo8h8fePXxAi5MXuaO7mW7w3R5grs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KDh7C55do5ivcBA9nFyZ6Ge1OpgYJD6Bv4uGVdbP2Tk9/rXh38gX1bqIdhf6NXiP0XjcDctBLUira+KxtguLEWW9IMx5KbuF4/wC9pU3wtqNc2zAIoOY/arLCb4svxAow/oHg2/bPB5mTcC9X3n0Wld+Kfk58Pn5Yyh2QIRUR3g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XhQCS2ob; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XhQCS2ob" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99B5AC113D0; Wed, 3 Dec 2025 11:08:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764760114; bh=t3W10qsRJTd3xYWo8h8fePXxAi5MXuaO7mW7w3R5grs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=XhQCS2obvmNKPGBY06kIZu5LLFLMx+5blL04pytjUsPg0V/oow+iVojGuqozLsImC azxrSjfXhkCpfCa2QIdb1gr+UAmlHcJCOXmmkOrEv8tluW86E3RbGFNV/xQmcUQ2iZ uXiUaeOFDnR4BzFiUv3CJLk890f+kjBmqxL1zsg9OM86KXG2Uz6lyqdkw+F0mLJVhV x0ez1mmTpfNHJ0dNXXE9aKB+D3+U21xsUp1HYghLGBtNBYuDCtgIu6emuNfLfQHbDn cGY6DjtaZzLJLvypVwUUwEOI0bo9V8rJGUsc96uWtUNL9TE3yTWlxYM0gaSkUsnzbk u30BN+0+hvFtg== Message-ID: Date: Wed, 3 Dec 2025 12:08:30 +0100 Precedence: bulk X-Mailing-List: devicetree-spec@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: SoC-specific device tree aliases? To: Matthias Schiffer Cc: Sascha Hauer , "devicetree@vger.kernel.org" , Conor Dooley , devicetree-spec@vger.kernel.org, quentin.schulz@cherry.de, Marc Kleine-Budde , "kernel@pengutronix.de" , Krzysztof Kozlowski , Ahmad Fatoum , Rob Herring References: <58816b68-3b09-4320-9a4e-09f2c2b2d0fa@kernel.org> <8ce701c9-6c8d-4b3e-8706-760b8aba89fc@kernel.org> <20251117-smooth-spiked-loon-52df28-mkl@pengutronix.de> <576a9eae-7dba-47d0-ad66-0a81d1893271@kernel.org> <9e14fb8e-af84-4072-b0ac-9ead882782be@kernel.org> <07ee3540-d0c1-436e-9e1d-db1952f609a6@kernel.org> <6638e499-2320-41c9-b720-faf4f976e476@kernel.org> <34bd1a0d8e579aba0a6a88039006500fe822ef3d.camel@ew.tq-group.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; keydata= xsFNBFVDQq4BEAC6KeLOfFsAvFMBsrCrJ2bCalhPv5+KQF2PS2+iwZI8BpRZoV+Bd5kWvN79 cFgcqTTuNHjAvxtUG8pQgGTHAObYs6xeYJtjUH0ZX6ndJ33FJYf5V3yXqqjcZ30FgHzJCFUu JMp7PSyMPzpUXfU12yfcRYVEMQrmplNZssmYhiTeVicuOOypWugZKVLGNm0IweVCaZ/DJDIH gNbpvVwjcKYrx85m9cBVEBUGaQP6AT7qlVCkrf50v8bofSIyVa2xmubbAwwFA1oxoOusjPIE J3iadrwpFvsZjF5uHAKS+7wHLoW9hVzOnLbX6ajk5Hf8Pb1m+VH/E8bPBNNYKkfTtypTDUCj NYcd27tjnXfG+SDs/EXNUAIRefCyvaRG7oRYF3Ec+2RgQDRnmmjCjoQNbFrJvJkFHlPeHaeS BosGY+XWKydnmsfY7SSnjAzLUGAFhLd/XDVpb1Een2XucPpKvt9ORF+48gy12FA5GduRLhQU vK4tU7ojoem/G23PcowM1CwPurC8sAVsQb9KmwTGh7rVz3ks3w/zfGBy3+WmLg++C2Wct6nM Pd8/6CBVjEWqD06/RjI2AnjIq5fSEH/BIfXXfC68nMp9BZoy3So4ZsbOlBmtAPvMYX6U8VwD TNeBxJu5Ex0Izf1NV9CzC3nNaFUYOY8KfN01X5SExAoVTr09ewARAQABzSVLcnp5c3p0b2Yg S296bG93c2tpIDxrcnprQGtlcm5lbC5vcmc+wsGVBBMBCgA/AhsDBgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgBYhBJvQfg4MUfjVlne3VBuTQ307QWKbBQJoF1BKBQkWlnSaAAoJEBuTQ307 QWKbHukP/3t4tRp/bvDnxJfmNdNVn0gv9ep3L39IntPalBFwRKytqeQkzAju0whYWg+R/rwp +r2I1Fzwt7+PTjsnMFlh1AZxGDmP5MFkzVsMnfX1lGiXhYSOMP97XL6R1QSXxaWOpGNCDaUl ajorB0lJDcC0q3xAdwzRConxYVhlgmTrRiD8oLlSCD5baEAt5Zw17UTNDnDGmZQKR0fqLpWy 786Lm5OScb7DjEgcA2PRm17st4UQ1kF0rQHokVaotxRM74PPDB8bCsunlghJl1DRK9s1aSuN hL1Pv9VD8b4dFNvCo7b4hfAANPU67W40AaaGZ3UAfmw+1MYyo4QuAZGKzaP2ukbdCD/DYnqi tJy88XqWtyb4UQWKNoQqGKzlYXdKsldYqrLHGoMvj1UN9XcRtXHST/IaLn72o7j7/h/Ac5EL 8lSUVIG4TYn59NyxxAXa07Wi6zjVL1U11fTnFmE29ALYQEXKBI3KUO1A3p4sQWzU7uRmbuxn naUmm8RbpMcOfa9JjlXCLmQ5IP7Rr5tYZUCkZz08LIfF8UMXwH7OOEX87Y++EkAB+pzKZNNd hwoXulTAgjSy+OiaLtuCys9VdXLZ3Zy314azaCU3BoWgaMV0eAW/+gprWMXQM1lrlzvwlD/k whyy9wGf0AEPpLssLVt9VVxNjo6BIkt6d1pMg6mHsUEVzsFNBFVDXDQBEADNkrQYSREUL4D3 Gws46JEoZ9HEQOKtkrwjrzlw/tCmqVzERRPvz2Xg8n7+HRCrgqnodIYoUh5WsU84N03KlLue MNsWLJBvBaubYN4JuJIdRr4dS4oyF1/fQAQPHh8Thpiz0SAZFx6iWKB7Qrz3OrGCjTPcW6ei OMheesVS5hxietSmlin+SilmIAPZHx7n242u6kdHOh+/SyLImKn/dh9RzatVpUKbv34eP1wA GldWsRxbf3WP9pFNObSzI/Bo3kA89Xx2rO2roC+Gq4LeHvo7ptzcLcrqaHUAcZ3CgFG88CnA 6z6lBZn0WyewEcPOPdcUB2Q7D/NiUY+HDiV99rAYPJztjeTrBSTnHeSBPb+qn5ZZGQwIdUW9 YegxWKvXXHTwB5eMzo/RB6vffwqcnHDoe0q7VgzRRZJwpi6aMIXLfeWZ5Wrwaw2zldFuO4Dt 91pFzBSOIpeMtfgb/Pfe/a1WJ/GgaIRIBE+NUqckM+3zJHGmVPqJP/h2Iwv6nw8U+7Yyl6gU BLHFTg2hYnLFJI4Xjg+AX1hHFVKmvl3VBHIsBv0oDcsQWXqY+NaFahT0lRPjYtrTa1v3tem/ JoFzZ4B0p27K+qQCF2R96hVvuEyjzBmdq2esyE6zIqftdo4MOJho8uctOiWbwNNq2U9pPWmu 4vXVFBYIGmpyNPYzRm0QPwARAQABwsF8BBgBCgAmAhsMFiEEm9B+DgxR+NWWd7dUG5NDfTtB YpsFAmgXUF8FCRaWWyoACgkQG5NDfTtBYptO0w//dlXJs5/42hAXKsk+PDg3wyEFb4NpyA1v qmx7SfAzk9Hf6lWwU1O6AbqNMbh6PjEwadKUk1m04S7EjdQLsj/MBSgoQtCT3MDmWUUtHZd5 RYIPnPq3WVB47GtuO6/u375tsxhtf7vt95QSYJwCB+ZUgo4T+FV4hquZ4AsRkbgavtIzQisg Dgv76tnEv3YHV8Jn9mi/Bu0FURF+5kpdMfgo1sq6RXNQ//TVf8yFgRtTUdXxW/qHjlYURrm2 H4kutobVEIxiyu6m05q3e9eZB/TaMMNVORx+1kM3j7f0rwtEYUFzY1ygQfpcMDPl7pRYoJjB dSsm0ZuzDaCwaxg2t8hqQJBzJCezTOIkjHUsWAK+tEbU4Z4SnNpCyM3fBqsgYdJxjyC/tWVT AQ18NRLtPw7tK1rdcwCl0GFQHwSwk5pDpz1NH40e6lU+NcXSeiqkDDRkHlftKPV/dV+lQXiu jWt87ecuHlpL3uuQ0ZZNWqHgZoQLXoqC2ZV5KrtKWb/jyiFX/sxSrodALf0zf+tfHv0FZWT2 zHjUqd0t4njD/UOsuIMOQn4Ig0SdivYPfZukb5cdasKJukG1NOpbW7yRNivaCnfZz6dTawXw XRIV/KDsHQiyVxKvN73bThKhONkcX2LWuD928tAR6XMM2G5ovxLe09vuOzzfTWQDsm++9UKF a/A= In-Reply-To: <34bd1a0d8e579aba0a6a88039006500fe822ef3d.camel@ew.tq-group.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 03/12/2025 11:36, Matthias Schiffer wrote: > On Wed, 2025-12-03 at 11:25 +0100, Krzysztof Kozlowski wrote: >> On 03/12/2025 11:16, Ahmad Fatoum wrote: >>> Hello Krzysztof, >>> >>> On 11/17/25 5:29 PM, Krzysztof Kozlowski wrote: >>>> On 17/11/2025 17:06, Rob Herring wrote: >>>>>> So you want it to be an ABI for barebox, sure, just make it a binding. >>>>> >>>>> What do you have in mind? Other than standard names for the aliases, >>>>> what can we check here? That a specific alias points to a specific >>>>> path? That would be a bit too much IMO. That would be equivalent to >>>>> specifying possible values in 'reg' for all devices. >>>> >>>> Binding with pattern or list of needed alias names, referenced by given >>>> soc-platform top-level schema. >>>> >>>> One of the points is to make it explicit and obvious (e.g. to Arnd or to >>>> me if I forget, because I follow the same logic of aliases per board) >>>> that these aliases are used outside of kernel. >>>> >>>> Just because ufs/mmc/spi can be used that way, does not mean we should >>>> accept any possible alias into soc.dtsi. >>> >>> I can't see how this could work. A number of boards renumber MMC devices >>> in a different manner than the SoC reference manual: >>> >>> - Changing the alias numbering is an ABI break, because Linux derives >>> its /dev/mmcblkX numbering from it >> >> First, why the alias would change? Isn't the board following the SoC >> numbering in 99.9% cases? > > At least for our TQ-Systems boards, we have a convention based on usage (mmc0: > eMMC, mmc1: SD card; serial0 is often the console) rather than following the SoC > numbering; that is, we're using the aliases as a form of hardware abstraction > rather than hardware description. Huh, does it even match numbering on the schematics / board / user-guides? I would prefer not to create bindings purely because some existing DTS code is not matching our expectations. However there could be a case where board numbering is different than soc number and we want to keep aliases configured for board. Basically what you propose here is the discouraged instance ID disguised under one more 'alias' which is not really alias. It's just an instance ID. There is no other use of soc-aliases beside instance ID. I see the problem you want to solve, I agree it is worth solving and I agree that DT is the place for this mapping between register value and device node. However solution of discouraged instance ID is just... well, discouraged, so not optimal. I don't have particular advice expect a dedicated property for each device in such case. Best regards, Krzysztof