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 A6C0A31196F; Mon, 27 Apr 2026 14:37:53 +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=1777300673; cv=none; b=CmswpkZHEJsgM7ztmqol5XH1zV39BfK9TsBA0zEyEUDGNouCT9Hy+nl7SmZ3J4R73bfISdQ9tJa83DBjb4HwtIU8qfgNgOraGcV60Q5v7Zsojd5PIgjg9qHNSd82Ea5tltupIAn0zqyxd9EB1EA5gTlKFAOFsgXS9JvsAG53+7A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777300673; c=relaxed/simple; bh=/zh0Wt5k0KjeFt6l4UoNKFAp5D/7oQ5SHJQxt9uh7x4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sqX/eLS5OqipjqwwJOXSAxu4EqdLmhhZKHKU7YkBGYfTq7/tPqJQuMjC7zRZo9/4+tQpmLPeSbDLj71AfUqKTXl3BEo84S6dGMFyXrMFAtk79Qx41NumX8sX0vofrvme/9BuSm3mwoUJlJZSHh6dcum68yxBYdzW89JB4oKQ3o8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IAfjW95O; 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="IAfjW95O" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE4AFC19425; Mon, 27 Apr 2026 14:37:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777300673; bh=/zh0Wt5k0KjeFt6l4UoNKFAp5D/7oQ5SHJQxt9uh7x4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=IAfjW95OzKS2EKDgoQICB3O7cL0706XXZHuDQhdRbhya4jx42dg9LkROS67MWhQWF 7ar3fgtLXa8JohZqQZyAxx0+8NpWfT2qVtTXWjeU12Y/+MilQWfnl2zp0OpDG7wjY1 oHof+ZqA1rjvmBE13Jc/se8KDNLY2qd1y7kunjTufqRhhlBEOM5Saj2MKum2qRqHTm jgtS3ExtaVpV83phNbJu9Lf8uGG7VN70vwap+bnXxbIJoksTtPtaggv4wr96qRoncm gUurDrqd4WRe4lahP8HBoB6kl1dSXAOGWr/XmWJ5Oa57+kWNDpIsZWpTAivhbqcYfm /Dfj0OTNsWxjw== Date: Mon, 27 Apr 2026 09:37:50 -0500 From: Rob Herring To: Conor Dooley Cc: Krzysztof Kozlowski , 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: <20260427143750.GA2491314-robh@kernel.org> References: <20260415082113.22775-2-krzysztof.kozlowski@oss.qualcomm.com> <20260415-rinsing-pushup-ba81cc249086@spud> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260415-rinsing-pushup-ba81cc249086@spud> On Wed, Apr 15, 2026 at 03:46:41PM +0100, Conor Dooley wrote: > 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: > > > > 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. > > > > 2. Device variant discovery through some means, like registers. > > > > Devices are incompatible and fallback is not suitable when that > > fallback cannot be used by the drivers to match/bind. > > > > Signed-off-by: Krzysztof Kozlowski > > --- > > Documentation/devicetree/bindings/writing-bindings.rst | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/Documentation/devicetree/bindings/writing-bindings.rst b/Documentation/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. > > > > - DO use fallback compatibles when devices are the same as or a superset of > > - prior implementations. > > + prior implementations. Fallback compatibles are applicable especially > > + when sharing a programming interface or when able to discover the > > + variants. > > + > > + - DON'T add fake fallback compatibles when software cannot use such to match > > + and bind to a device, and still operate correctly. > > > > - 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. Can you respin with Conor's addition. Rob