linux-kernel - Re: [PATCH] iio: cros_ec_accel_legacy: Mark expected switch fall-throughs

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Message-ID: <20190220183425.202d4d40@archlinux>
Date:   Wed, 20 Feb 2019 18:34:25 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Gwendal Grignou <gwendal@...omium.org>
Subject: Re: [PATCH] iio: cros_ec_accel_legacy: Mark expected switch
 fall-throughs

On Wed, 20 Feb 2019 10:20:39 -0800
Kees Cook <keescook@...omium.org> wrote:

> On Mon, Oct 8, 2018 at 10:24 AM Gustavo A. R. Silva
> <gustavo@...eddedor.com> wrote:
> >
> > In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> > where we are expecting to fall through.
> >
> > Addresses-Coverity-ID: 1397962 ("Missing break in switch")
> > Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> > ---
> >  drivers/iio/accel/cros_ec_accel_legacy.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/iio/accel/cros_ec_accel_legacy.c b/drivers/iio/accel/cros_ec_accel_legacy.c
> > index 063e89e..d609654 100644
> > --- a/drivers/iio/accel/cros_ec_accel_legacy.c
> > +++ b/drivers/iio/accel/cros_ec_accel_legacy.c
> > @@ -385,8 +385,10 @@ static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
> >                 switch (i) {
> >                 case X:
> >                         ec_accel_channels[X].scan_index = Y;
> > +                       /* fall through */
> >                 case Y:
> >                         ec_accel_channels[Y].scan_index = X;
> > +                       /* fall through */
> >                 case Z:
> >                         ec_accel_channels[Z].scan_index = Z;
> >                 }  
> 
> Shouldn't these actually be "break;"s ? It seems like the loop is
> stepping through X, Y, and Z. The _result_ is accidentally the same:
> 
> X: set X, Y, and Z
> Y: set Y and Z
> Z: set Z
> 
> result: X, Y, and Z are set correctly. But the code is technically wrong.
> 

Agreed, it's 'novel'.  Waiting for Gwendal or someone else to come
back and check it wasn't meant to be doing something else.

Jonathan

>