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 C79642EDD6C; Fri, 13 Feb 2026 07:31:26 +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=1770967886; cv=none; b=qTrqb9PkKlJQm2EPm3P35XudBbDVKYsll1iXVSz/PilXOVL9iUC6qs9ckWsbjWIvB3vncB3Km41lPoiAFBGSuxJeJgMvRV4TEGtwhtPWkFctOk2vSDLgAjorYm7fYsXd70f7Ln0TIykyYi9O7ik3HGkjwBNlYLxTgp4veOI8T18= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770967886; c=relaxed/simple; bh=3iSHqIIGc2oCL1GreIg38gwbcTI18P0/tbeSnaPrzYk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fJR91evXPFuB4VKKRVKjyZlut7r2E6KZ+ed+3WsIjAqy6ptequoIOOCMZa7k4IVqYuvjXraFGxP40M0hEo1PgjkETx9nbEZfAQnxk76quR5dKWgIv03ZGUFF0EiD6eBcUE7SzHMLSJ8SYVE1zoEzEDtH0YXDhaIAN7Y0Mlx6iQw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JK07CpyS; 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="JK07CpyS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A44E8C116C6; Fri, 13 Feb 2026 07:31:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770967886; bh=3iSHqIIGc2oCL1GreIg38gwbcTI18P0/tbeSnaPrzYk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JK07CpySM4RnY1VWXT7aCjX3BfIzi/vlg3hYpdrngWmj8zklHqwEKpjZQ5TkO8X9U /fE20ytVaI+yvUXVJwDHhQKBWF/8a0mh1IS9xXBKvyhfPpoBHECEn1z5ESZPQJ0f2H ySivGfQFXTskv8U5jXDx15cLjWyy3o+bNYBMgzEuJzYLEQMYmKtFJ2WHfaxAnMdYPp 71wjgF9dkaPo2CC4bONxvZRjWMG9F01gVNf+0o6xPO/Vqd+LfE2pogT8Q0Vqo1nSYB Fz9Bogx3R2skbPykGucaMnGDzMWUPpi7fHwEQJ/7b7U9mrsZXzqrPnW4uRfPIHkT0S UjLvXY68X5uEA== Message-ID: <89c0dd51-fdd5-4368-b5f5-615143ffd166@kernel.org> Date: Fri, 13 Feb 2026 08:31:21 +0100 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: [PATCH v2 2/2] gpio: aggregator: add gpio-aggregator DT compatible To: James Hilliard , Geert Uytterhoeven , Bartosz Golaszewski Cc: Rob Herring , linux-gpio@vger.kernel.org, Linus Walleij , Krzysztof Kozlowski , Conor Dooley , Alexander Stein , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Herve Codina References: <20260211081355.3028947-1-james.hilliard1@gmail.com> <20260211081355.3028947-2-james.hilliard1@gmail.com> <34a9b531-4f53-47ee-861e-1b18ff1a5752@kernel.org> <20260211214708.GA3947691-robh@kernel.org> <9afa52c1-b7de-4ccb-9114-a142567d21af@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 12/02/2026 20:16, James Hilliard wrote: > On Thu, Feb 12, 2026 at 12:18 AM Krzysztof Kozlowski wrote: >> >> On 11/02/2026 22:49, James Hilliard wrote: >>>>>>> >>>>>>> Regardless of the DT bindings - this change is perfectly fine. We do >>>>>> >>>>>> You cannot have compatible without DT bindings, so this alone is not >>>>>> "perfectly fine". Maybe you wanted platform_device_id entry for >>>>>> ACPI/legacy/MFD devices? >>>>>> >>>>> >>>>> Sure you can, you just can't put it into upstream devicetree sources. >>>>> We have had a compatible for gpio-sim for testing purposes for years. >>>>> Why would it be illegal to enable matching of platform drivers over DT >>>>> for testing purposes? >>>> >>>> The primary issue is undocumented ones show up in 'make >>>> dt_compatible_check'. I would like that to be warning free. >>> >>> Would adding it here make sense? >>> https://github.com/torvalds/linux/blob/v6.19/Documentation/devicetree/bindings/incomplete-devices.yaml#L243-L245 >> >> What would you like to achieve with that? The binding patch did not have >> rationale why do we want it and here is the same question - what sort of >> problem is being solved by adding it to incomplete (so wrong) devices? > > See details for what I'm trying to accomplish with gpio-aggregator: > https://lore.kernel.org/all/CADvTj4oBtO0Yhib1rE8QQwgtJvy-x_hK46C63mjVAydtxHOV8g@mail.gmail.com/ I don't think that putting it into incomplete-devices would help you. I assume you read the binding... You still could not use that compatible in any upstreamable DTS code, even if this is only an overlay. You would have warnings... > > I'm basically trying to use it for the reasons described here: > https://bootlin.com/blog/gpio-aggregator-a-virtual-gpio-chip/ > > Is there a different device tree mechanism that can be used to > name individual gpio lines on a gpiochip without having to name > all of them for non-hog lines? > > I'm confused why a "gpio-delay" compatible is allowed but one > without the delay param is not? > > Or is the issue just with the name of the compatible I used being > called "gpio-aggregator"? No, the issue is that there is no hardware you are trying represent in DTS. > >> This is not a pure virtual device, but for use with actual hardware. >> >> Nacked-by: Geert Uytterhoeven > > I'm trying to use this with actual hardware, I just called it "virtual" > because that's how it was described in the bootlin blog post. > > I'm confused about what the issue is here as "gpio-delay" is also > a virtual device in the same way. gpio-delay IS NOT a virtual device. You can even touch it. Can I touch your gpio-aggregator? > >> Well, it is a virtual device in that there's no actual "aggregator" >> device on the board. It virtually aggregates GPIOs into a separate >> chip for user's convenience. While there's no such device as a >> gpio-aggregator - and so we must not put it into bindings nor into >> mainline devicetree sources - having a compatible matching in the >> driver is perfectly fine IMO. Just like gpio-sim. > > There's no such "gpio-delay" device either right? I'm confused There is. > why that compatible can exist but one without the delay param can > not in the mainline sources. Aren't they both virtual devices? Best regards, Krzysztof