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From:   Anders Roxell <anders.roxell@linaro.org>
Date:   Tue, 21 Dec 2021 13:24:38 +0100
Message-ID: <CADYN=9K8fD7sSdTy+mCY6dvjutabLnibs3BoAmv1W4sKcPLpXw@mail.gmail.com>
Subject: Re: [PATCH 4.19 6/6] Input: touchscreen - avoid bitwise vs logical OR warning
To:     Greg KH <greg@kroah.com>
Cc:     stable@vger.kernel.org, linux-kernel@vger.kernel.org,
        woojung.huh@microchip.com, UNGLinuxDriver@microchip.com,
        davem@davemloft.net, netdev@vger.kernel.org,
        linux-usb@vger.kernel.org, clang-built-linux@googlegroups.com,
        ulli.kroll@googlemail.com, linux@armlinux.org.uk,
        linux-arm-kernel@lists.infradead.org, amitkarwar@gmail.com,
        nishants@marvell.com, gbhat@marvell.com, huxinming820@gmail.com,
        kvalo@codeaurora.org, linux-wireless@vger.kernel.org,
        rostedt@goodmis.org, mingo@redhat.com, dmitry.torokhov@gmail.com,
        ndesaulniers@google.com, nathan@kernel.org,
        linux-input@vger.kernel.org
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On Mon, 20 Dec 2021 at 11:59, Greg KH <greg@kroah.com> wrote:
>
> On Fri, Dec 17, 2021 at 03:41:19PM +0100, Anders Roxell wrote:
> > From: Nathan Chancellor <nathan@kernel.org>
> >
> > commit a02dcde595f7cbd240ccd64de96034ad91cffc40 upstream.
> >
> > A new warning in clang points out a few places in this driver where a
> > bitwise OR is being used with boolean types:
> >
> > drivers/input/touchscreen.c:81:17: warning: use of bitwise '|' with boolean operands [-Wbitwise-instead-of-logical]
> >         data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
> >                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > This use of a bitwise OR is intentional, as bitwise operations do not
> > short circuit, which allows all the calls to touchscreen_get_prop_u32()
> > to happen so that the last parameter is initialized while coalescing the
> > results of the calls to make a decision after they are all evaluated.
> >
> > To make this clearer to the compiler, use the '|=' operator to assign
> > the result of each touchscreen_get_prop_u32() call to data_present,
> > which keeps the meaning of the code the same but makes it obvious that
> > every one of these calls is expected to happen.
> >
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > Reported-by: Nick Desaulniers <ndesaulniers@google.com>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > Link: https://lore.kernel.org/r/20211014205757.3474635-1-nathan@kernel.org
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
> > ---
> >  drivers/input/touchscreen/of_touchscreen.c | 18 +++++++++---------
> >  1 file changed, 9 insertions(+), 9 deletions(-)
>
> Also needed in 5.10.y and 5.4.y.
>
> Please be more careful next time.

Yes I will, I'm sorry.

Cheers,
Anders