linux-kernel - Re: [GIT PULL] Driver core patches for 5.1-rc1

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Date:   Wed, 6 Mar 2019 15:47:11 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Greg KH <gregkh@...uxfoundation.org>, Joe Perches <joe@...ches.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>
Subject: Re: [GIT PULL] Driver core patches for 5.1-rc1

On Wed, Mar 6, 2019 at 2:33 AM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> Joe Perches (1):
>       device.h: Add __cold to dev_<level> logging functions

This is very funky, but that commit generates a new warning in a
totally unrelated area:

  drivers/iio/adc/qcom-pm8xxx-xoadc.c: In function ‘pm8xxx_xoadc_probe’:
  drivers/iio/adc/qcom-pm8xxx-xoadc.c:633:8: warning: ‘ch’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
    ret = pm8xxx_read_channel_rsv(adc, ch, AMUX_RSV4,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             &read_nomux_rsv4, true);
             ~~~~~~~~~~~~~~~~~~~~~~~
  drivers/iio/adc/qcom-pm8xxx-xoadc.c:426:27: note: ‘ch’ was declared here
    struct pm8xxx_chan_info *ch;
                             ^~

and it all looks entirely insane if you look at that line 633 where
the ostensibly uninitialized variable is (it clearly _is_ initialized
there), but if you then look at that line 426 you notice that it
actually makes some kind of sense. The value comes from another
function that was apparently inlined, and that other function does not
"obviously" initialize it.

I wonder why this wasn't seen in linux-next? Yes, the connection is
odd, and maybe it's very compiler version dependent, but I do hope
people react to new warnings. The kernel is entirely warning-free for
me for an x86-64 allmodconfig build, and I want to keep it that way.

And _because_ I want to keep it that way (one of the things I do
during the merge window is look for oddities coming in during pulls,
and new warnings is a big deal for me), I applied the attached patch.
Just FYI.

                   Linus

View attachment "0001-iio-adc-fix-warning-in-Qualcomm-PM8xxx-HK-XOADC-driv.patch" of type "text/x-patch" (2850 bytes)