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Date:   Fri, 23 Jul 2021 10:17:30 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Serge Semin <fancer.lancer@gmail.com>
Cc:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        John Stultz <john.stultz@linaro.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
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        Felipe Balbi <balbi@kernel.org>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Andy Gross <agross@kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
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        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Amit Pundir <amit.pundir@linaro.org>
Subject: Re: [PATCH 29/29] arm64: dts: qcom: Harmonize DWC USB3 DT nodes name
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On Fri, Jul 23, 2021 at 12:54:51AM +0300, Serge Semin wrote:
> I always thought that ABI is supposed to be something what is
> thoroughly documented and firmly declared to be so. It isn't something
> claimed to be on a random nature but defined to be one when it's
> more-or-less standardized. Thus the Linux kernel developers decide not
> to change something unless it went through the series of iterations like
> testing, stable, obsolete, remove. As I see it the rule-of-thumb is
> supposed to be as "nothing is ABI unless it's declared as such".

Not true at all.  Again, if something works in an older kernel version,
and you upgrade to a new kernel version and it breaks, that is a
regression and must be fixed/reverted.

Lack of documentation does not mean an ABI can be changed.

greg k-h