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[78.26.46.173]) by smtp.gmail.com with ESMTPSA id 197-20020a2e05ce000000b0025d70efeaaasm3912382ljf.75.2022.07.27.05.12.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Jul 2022 05:12:10 -0700 (PDT) Message-ID: Date: Wed, 27 Jul 2022 14:12:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH v2 3/9] arm64: dts: bcmbca: update BCM4908 board dts files Content-Language: en-US To: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , William Zhang Cc: Rob Herring , Linux ARM List , joel.peshkin@broadcom.com, f.fainelli@gmail.com, Broadcom Kernel List , dan.beygelman@broadcom.com, anand.gore@broadcom.com, kursad.oney@broadcom.com, Krzysztof Kozlowski , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220725055402.6013-1-william.zhang@broadcom.com> <20220725055402.6013-4-william.zhang@broadcom.com> <20220725233238.GA2960972-robh@kernel.org> <1004391f-fb6c-5f84-de28-8f76dc3471e5@broadcom.com> <0af44be8f5802e66011b4642de4632d4@milecki.pl> From: Krzysztof Kozlowski In-Reply-To: <0af44be8f5802e66011b4642de4632d4@milecki.pl> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/07/2022 12:39, Rafał Miłecki wrote: > On 2022-07-26 03:09, William Zhang wrote: >> On 07/25/2022 04:32 PM, Rob Herring wrote: >>> On Sun, Jul 24, 2022 at 10:53:56PM -0700, William Zhang wrote: >>>> Append "brcm,bcmbca" to compatible strings based on the new bcmbca >>>> binding rule for BCM4908 family based boards. This will break drivers >>>> that use the old compatible string for binding. Fortunately there is >>>> no >>>> such usage in linux and u-boot. >>> >>> How does adding an additional compatible break things? >>> In theory when some crazy code tries to match the entire string. But >>> not >> in linux, u-boot code and hopefully not in other bootloader and Os >> does that. But this does change an existing compatible string so >> Krzysztof suggested to add comment about the breakage in the commit >> message. I can remove this and send v3 if you guys think it is >> necessary. > > Krzysztof commented on ABI breakage [1] when you tried removing > "brcm,bcm4908" from the "compatible" list in your patch > [RFC PATCH 3/3] arm64: dts: bcmbca: update bcm4808 board dts file [2] > > In this version of your patch you don't remove "brcm,bcm4908" anymore so > this change doesn't break anything. Adding a new "compatible" string > doesn't break things. You can remove that info from the commit message. Thanks... It is second thing (after not existing Reviewed-by) attributed to me by William, although here probably by misunderstanding... So for clarity (obvious stuff is not always obvious to everyone): 1. Removal of compatible is an ABI break. 2. Add of compatible is not an ABI break. See also: https://elixir.bootlin.com/linux/v5.19-rc8/source/Documentation/devicetree/bindings/ABI.rst#L26 Best regards, Krzysztof