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[2001:470:b8f6:1b::1]) by smtp.gmail.com with ESMTPSA id p84-20020acaf157000000b00342df642fd3sm916967oih.48.2022.08.08.05.26.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Aug 2022 05:26:54 -0700 (PDT) Sender: Corey Minyard Received: from minyard.net (unknown [IPv6:2001:470:b8f6:1b:3153:e085:df0f:abc2]) by serve.minyard.net (Postfix) with ESMTPSA id A861A1800FA; Mon, 8 Aug 2022 12:26:53 +0000 (UTC) Date: Mon, 8 Aug 2022 07:26:52 -0500 From: Corey Minyard To: Krzysztof Kozlowski Cc: Tomer Maimon , avifishman70@gmail.com, tali.perry1@gmail.com, joel@jms.id.au, venture@google.com, yuenn@google.com, benjaminfair@google.com, jic23@kernel.org, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, openbmc@lists.ozlabs.org, openipmi-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v3] dt-binding: ipmi: add fallback to npcm845 compatible Message-ID: <20220808122652.GO3834@minyard.net> Reply-To: minyard@acm.org References: <20220808075452.115907-1-tmaimon77@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Mon, Aug 08, 2022 at 11:11:16AM +0300, Krzysztof Kozlowski wrote: > On 08/08/2022 09:54, Tomer Maimon wrote: > > Add to npcm845 KCS compatible string a fallback to npcm750 KCS compatible > > string becuase NPCM845 and NPCM750 BMCs are using identical KCS modules. > > > > Fixes: 84261749e58a ("dt-bindings: ipmi: Add npcm845 compatible") > > Signed-off-by: Tomer Maimon > > > Acked-by: Krzysztof Kozlowski Ok, I think I understand how this is supposed to work. It's not altogether clear from the device tree documentation. It says in Documentation/devicetree/bindings/writing-bindings.rst: - DO make 'compatible' properties specific. DON'T use wildcards in compatible strings. DO use fallback compatibles when devices are the same as or a subset of prior implementations. DO add new compatibles in case there are new features or bugs. AFAICT, there are no new features or bugs, just a new SOC with the same device. In general usage I have seen, you would just use the same compatible. However, if I understand this, that last sentence should say: DO add new compatibles in case there is a new version of hardware with the possibility of new features and/or bugs. Also, the term "specific" is, ironically, vague. Specific to what? It would be nice to have something added to "Typical cases and caveats" that says: - If you are writing a binding for a new device that is the same as, or a superset of another existing device, add a new specific compatible for the new device followed by a compatible for the existing device. That way, if the device has new bugs or new specific features are added, you can add workarounds without modifying the device tree. Anyway, I have added this to my tree with your ack. -corey > > > Best regards, > Krzysztof