linux-kernel - Re: [PATCH v2 03/14] staging: iio: ad7746: Fix bound checkings

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Message-ID: <20180418103948.00004b93@huawei.com>
Date:   Wed, 18 Apr 2018 10:39:48 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Hernán Gonzalez <hernan@...guardiasur.com.ar>
CC:     Jonathan Cameron <jic23@...nel.org>, <knaack.h@....de>,
        <lars@...afoo.de>, Peter Meerwald-Stadler <pmeerw@...erw.net>,
        <gregkh@...uxfoundation.org>, <Michael.Hennerich@...log.com>,
        <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 03/14] staging: iio: ad7746: Fix bound checkings

On Mon, 16 Apr 2018 11:47:05 -0300
Hernán Gonzalez <hernan@...guardiasur.com.ar> wrote:

> On Sun, Apr 15, 2018 at 12:05 PM, Jonathan Cameron <jic23@...nel.org> wrote:
> > On Fri, 13 Apr 2018 13:36:40 -0300
> > Hernán Gonzalez <hernan@...guardiasur.com.ar> wrote:
> >  
> >> Also remove unnecessary parenthesis  
> > I am probably missing something.  I'm not sure what you mean
> > by fix bound checking?   There are superfluous brackets, but
> > I don't see any functional change to indicate there was anything
> > wrong with the original checks.
> >  
> 
> Maybe I'm wrong but | is a bitwise operator while || is a logical one.
> There are no functional changes as you said but, from K&R, "One must
> distinguish the bitwise operators & and | from the logical operators
> && and II, which imply left-to-right evaluation of a truth value. For
> example, if x is 1 and y is 2, then x & y is zero while x && y is one"
> so it'd be slightly faster if the first condition is true, and it
> would be the "correct" operator to use in this case, even though it
> doesn't affect the result.
Got you, I missed the operator change entirely. Doh.

Jonathan

> 
> >>
> >> Signed-off-by: Hernán Gonzalez <hernan@...guardiasur.com.ar>
> >> ---
> >>  drivers/staging/iio/cdc/ad7746.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c
> >> index 516aa93..d793785 100644
> >> --- a/drivers/staging/iio/cdc/ad7746.c
> >> +++ b/drivers/staging/iio/cdc/ad7746.c
> >> @@ -458,7 +458,7 @@ static int ad7746_write_raw(struct iio_dev *indio_dev,
> >>               ret = 0;
> >>               break;
> >>       case IIO_CHAN_INFO_CALIBBIAS:
> >> -             if ((val < 0) | (val > 0xFFFF)) {
> >> +             if (val < 0 || val > 0xFFFF) {
> >>                       ret = -EINVAL;
> >>                       goto out;
> >>               }
> >> @@ -470,7 +470,7 @@ static int ad7746_write_raw(struct iio_dev *indio_dev,
> >>               ret = 0;
> >>               break;
> >>       case IIO_CHAN_INFO_OFFSET:
> >> -             if ((val < 0) | (val > 43008000)) { /* 21pF */
> >> +             if (val < 0 || val > 43008000) { /* 21pF */
> >>                       ret = -EINVAL;
> >>                       goto out;
> >>               }  
> >  
> --
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