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 CE7A33806A6; Wed, 15 Apr 2026 14:46:45 +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=1776264405; cv=none; b=vCDRgSjEruYQiP11rV6hvShfDiWgmseTZTGz6BrCGyAslQ0l8TLP8oPDLG89BNfAfMQrkVUNaU8e2nT9tu4VMAllY8WxsjmFumphUwsbvPsCa/dUs4d6USQ1y584JYPBnRceC1Jgh+wjwUlfMCvEVOolmN3/O8tJxD68/1ymrFY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776264405; c=relaxed/simple; bh=Df7sEiD8rbNH6f0QBcSo3vTb6HODcM2EnP8UyOVA41E=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=S34+gkXeuTFPX+lhkU4JWOK0FVtbdK3xgHzPtQbGnYEmNXqXLov9oJZ4rNx+hlenSVchGa/kx5HChnDsSzx2/b+yCUnLFwiVrkLr7dMHTwBju/0Kr6EegxH+uLGURbOSpAcRlRSctQ21UWS3gXrOgRpixGxmKMyakbd+jZXHjww= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=imhi3uH/; 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="imhi3uH/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 270C4C19424; Wed, 15 Apr 2026 14:46:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776264405; bh=Df7sEiD8rbNH6f0QBcSo3vTb6HODcM2EnP8UyOVA41E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=imhi3uH/P1Uk8JSR4e8nhvpxP8FWN81LoH+HThxxyjhX7rUikV3bEhMjkw7tF5XVr g/90NVeCDRg6BKZr5FCK/swpvo26dGdFmE7evnOt39963JkFM0JgT2uG84vZnKHYPi EvhFotZ07UfkSgELBBYR/o2t7NTPmvklWn4JJlwsBUHgmriPsiJfKj6xyvTCgXKliu DOBt2oijMs24n4DFMmVtVIolR4D3RX9PgjSgLUWF4A2ark/+Aze9iDfZHIDJOxZUpf xOnfBwcmJFTa9bbkEDdySJ/Dyi7//jqUciQBxDGMZomK78arKIr6JHZG+5Bkb6+xpt ER2TinS0PaCzA== Date: Wed, 15 Apr 2026 15:46:41 +0100 From: Conor Dooley To: Krzysztof Kozlowski Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] docs: dt: writing-bindings: Extend compatible fallbacks guideline Message-ID: <20260415-rinsing-pushup-ba81cc249086@spud> References: <20260415082113.22775-2-krzysztof.kozlowski@oss.qualcomm.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="PL4PO5LQw84Z+gcI" Content-Disposition: inline In-Reply-To: <20260415082113.22775-2-krzysztof.kozlowski@oss.qualcomm.com> --PL4PO5LQw84Z+gcI Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 15, 2026 at 10:21:14AM +0200, Krzysztof Kozlowski wrote: > Extend the guidelines when to use fallback compatibles to cover to > common review responses. Devices are most likely compatible and should > use fallbacks when having: >=20 > 1. Compatible programming interface, meaning one is a subset, and Linux > device drivers can use the subset to correctly match/bind and still > operate with the subset features. >=20 > 2. Device variant discovery through some means, like registers. >=20 > Devices are incompatible and fallback is not suitable when that > fallback cannot be used by the drivers to match/bind. >=20 > Signed-off-by: Krzysztof Kozlowski > --- > Documentation/devicetree/bindings/writing-bindings.rst | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) >=20 > diff --git a/Documentation/devicetree/bindings/writing-bindings.rst b/Doc= umentation/devicetree/bindings/writing-bindings.rst > index 667816dd7d50..03e29e2d50af 100644 > --- a/Documentation/devicetree/bindings/writing-bindings.rst > +++ b/Documentation/devicetree/bindings/writing-bindings.rst > @@ -53,7 +53,12 @@ Properties > - DON'T use wildcards or device-family names in compatible strings. > =20 > - DO use fallback compatibles when devices are the same as or a super= set of > - prior implementations. > + prior implementations. Fallback compatibles are applicable especia= lly > + when sharing a programming interface or when able to discover the > + variants. > + > + - DON'T add fake fallback compatibles when software cannot use such t= o match > + and bind to a device, and still operate correctly. > =20 > - DO add new compatibles in case there are new features or bugs. Acked-by: Conor Dooley - DO use the commit message explain why devices that may appear compatible in a diff (e.g. no differences in property use) but are not compatible, are not compatible. --PL4PO5LQw84Z+gcI Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCad+k0QAKCRB4tDGHoIJi 0tgKAQDDSNRcnSCt2aP42OSv1ldhVWCslyiVM9CvkMjzoxMfqQD8D99oiara1TOl aVrvBc2U0Gotu8IVpv7qiMWHcMfBBQE= =A5BV -----END PGP SIGNATURE----- --PL4PO5LQw84Z+gcI--