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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Wed, 1 Apr 2020 12:13:59 -0700
Message-ID: <CAKwvOdn7TpsZJ70mRiQARJc9Fy+364PXSAiPnSpc_M9pOaXjGw@mail.gmail.com>
Subject: Re: [PATCH v3] bitfield.h: add FIELD_MAX() and field_max()
To:     Alex Elder <elder@linaro.org>
Cc:     Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        "David S. Miller" <davem@davemloft.net>,
        Johannes Berg <johannes@sipsolutions.net>,
        Jakub Kicinski <kuba@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Network Development <netdev@vger.kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>
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On Wed, Apr 1, 2020 at 11:24 AM Alex Elder <elder@linaro.org> wrote:
>
> On 4/1/20 12:35 PM, Nick Desaulniers wrote:
> >> Define FIELD_MAX(), which supplies the maximum value that can be
> >> represented by a field value.  Define field_max() as well, to go
> >> along with the lower-case forms of the field mask functions.
> >>
> >> Signed-off-by: Alex Elder <elder@linaro.org>
> >> Acked-by: Jakub Kicinski <kuba@kernel.org>
> >> ---
> >> v3: Rebased on latest netdev-next/master.
> >>
> >> David, please take this into net-next as soon as possible.  When the
> >> IPA code was merged the other day this prerequisite patch was not
> >> included, and as a result the IPA driver fails to build.  Thank you.
> >>
> >>   See: https://lkml.org/lkml/2020/3/10/1839
> >>
> >>                                      -Alex
> >
> > In particular, this seems to now have regressed into mainline for the 5.7
> > merge window as reported by Linaro's ToolChain Working Group's CI.
> > Link: https://github.com/ClangBuiltLinux/linux/issues/963
>
> Is the problem you're referring to the result of a build done
> in the midst of a bisect?
>
> The fix for this build error is currently present in the
> torvalds/linux.git master branch:
>     6fcd42242ebc soc: qcom: ipa: kill IPA_RX_BUFFER_ORDER

Is that right? That patch is in mainline, but looks unrelated to what
I'm referring to.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6fcd42242ebcc98ebf1a9a03f5e8cb646277fd78
From my github link above, the issue I'm referring to is a
-Wimplicit-function-declaration warning related to field_max.
6fcd42242ebc doesn't look related.

>
> I may be mistaken, but I believe this is the same problem I discussed
> with Maxim Kuvyrkov this morning.  A different build problem led to
> an automated bisect, which conluded this was the cause because it
> landed somewhere between the initial pull of the IPA code and the fix
> I reference above.

Yes, Maxim runs Linaro's ToolChain Working Group (IIUC, but you work
there, so you probably know better than I do), that's the CI I was
referring to.

I'm more concerned when I see reports of regressions *in mainline*.
The whole point of -next is that warnings reported there get fixed
BEFORE the merge window opens, so that we don't regress mainline.  Or
we drop the patches in -next.
-- 
Thanks,
~Nick Desaulniers