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
