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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 29 Oct 2019 10:05:15 +0100
Message-ID: <CAMuHMdUCx31k3VJt=nYSkFXcOQdRhH7FiY8_f5RX4w4zaksP-w@mail.gmail.com>
Subject: Re: linux-next: build warning after merge of the thermal tree
To:     Stephen Rothwell <sfr@canb.auug.org.au>
Cc:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Linux Next Mailing List <linux-next@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Amit Kucheria <amit.kucheria@linaro.org>
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On Tue, Oct 22, 2019 at 1:25 AM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> After merging the thermal tree, today's linux-next build (x86_64
> allmodconfig) produced this warning:
>
> In file included from drivers/thermal/qcom/tsens-common.c:13:
> drivers/thermal/qcom/tsens-common.c: In function 'tsens_set_interrupt':
> include/linux/regmap.h:87:2: warning: 'index' may be used uninitialized in this function [-Wmaybe-uninitialized]
>    87 |  regmap_field_update_bits_base(field, ~0, val, NULL, false, false)
>       |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/thermal/qcom/tsens-common.c:183:6: note: 'index' was declared here
>   183 |  u32 index;
>       |      ^~~~~
> In file included from drivers/thermal/qcom/tsens-common.c:13:
> include/linux/regmap.h:87:2: warning: 'index_clear' may be used uninitialized in this function [-Wmaybe-uninitialized]
>    87 |  regmap_field_update_bits_base(field, ~0, val, NULL, false, false)
>       |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/thermal/qcom/tsens-common.c:199:18: note: 'index_clear' was declared here
>   199 |  u32 index_mask, index_clear;
>       |                  ^~~~~~~~~~~
> drivers/thermal/qcom/tsens-common.c:199:6: warning: 'index_mask' may be used uninitialized in this function [-Wmaybe-uninitialized]
>   199 |  u32 index_mask, index_clear;
>       |      ^~~~~~~~~~
>
> Introduced by commit
>
>   fbfe1a042cfd ("drivers: thermal: tsens: Add interrupt support")

And kisskb reported the following link failure on m68k:

    ERROR: "__udivdi3" [drivers/thermal/qcom/qcom_tsens.ko] undefined!

Probably caused by a plain 64-bit division in the code.
I expect this shows up on other 32-bit platforms, too.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds