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

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Message-ID: <CALfa3vFgh7jtb=B6doOu-y2Bm77wu4zVdLE1LuxbruTTKjLU=A@mail.gmail.com>
Date:   Mon, 16 Apr 2018 11:47:05 -0300
From:   Hernán Gonzalez <hernan@...guardiasur.com.ar>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     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 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.

>>
>> 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;
>>               }
>