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Re: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

Started byJonathan Cameron <jic23@kernel.org>
First post2017-04-02 11:30 +0200
Last post2017-04-02 12:20 +0200
Articles 3 — 2 participants

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  Re: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative  values Jonathan Cameron <jic23@kernel.org> - 2017-04-02 11:30 +0200
    Re: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative  values Lars-Peter Clausen <lars@metafoo.de> - 2017-04-02 12:10 +0200
      Re: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative  values Jonathan Cameron <jic23@kernel.org> - 2017-04-02 12:20 +0200

#1614684 — Re: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

FromJonathan Cameron <jic23@kernel.org>
Date2017-04-02 11:30 +0200
SubjectRe: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values
Message-ID<trJZE-71T-15@gated-at.bofh.it>
On 25/03/17 18:03, Jonathan Cameron wrote:
> On 24/03/17 12:41, Nikolaus Schulz wrote:
>> Fix formatting of negative values of type IIO_VAL_FRACTIONAL_LOG2 by
>> switching from do_div(), which can't handle negative numbers, to
>> div_s64_rem().  Also use shift_right for shifting, which is safe with
>> negative values.
>>
>> Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
>> Cc: stable@vger.kernel.org
> Looks sane to me, but I'd like to give others time to comment on this
> just in case there is some odd condition neither of us has thought of!
> 
> Give me a poke if we get nothing else for a few weeks.
Lars, I think this might have been your magic in the first place.

Could you sanity check this one please. It's in the category of very
risky of both Nikolaus and I have missed something!

Thanks,

Jonathan
> 
> Jonathan
>> ---
>>  drivers/iio/industrialio-core.c | 7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
>> index d18ded4..3ff91e0 100644
>> --- a/drivers/iio/industrialio-core.c
>> +++ b/drivers/iio/industrialio-core.c
>> @@ -610,10 +610,9 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
>>  		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
>>  		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>>  	case IIO_VAL_FRACTIONAL_LOG2:
>> -		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
>> -		tmp1 = do_div(tmp, 1000000000LL);
>> -		tmp0 = tmp;
>> -		return snprintf(buf, len, "%d.%09u", tmp0, tmp1);
>> +		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
>> +		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
>> +		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>>  	case IIO_VAL_INT_MULTIPLE:
>>  	{
>>  		int i;
>>
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

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#1614691

FromLars-Peter Clausen <lars@metafoo.de>
Date2017-04-02 12:10 +0200
Message-ID<trKCm-7vQ-9@gated-at.bofh.it>
In reply to#1614684
On 04/02/2017 11:26 AM, Jonathan Cameron wrote:
> On 25/03/17 18:03, Jonathan Cameron wrote:
>> On 24/03/17 12:41, Nikolaus Schulz wrote:
>>> Fix formatting of negative values of type IIO_VAL_FRACTIONAL_LOG2 by
>>> switching from do_div(), which can't handle negative numbers, to
>>> div_s64_rem().  Also use shift_right for shifting, which is safe with
>>> negative values.
>>>
>>> Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
>>> Cc: stable@vger.kernel.org
>> Looks sane to me, but I'd like to give others time to comment on this
>> just in case there is some odd condition neither of us has thought of!
>>
>> Give me a poke if we get nothing else for a few weeks.
> Lars, I think this might have been your magic in the first place.
> 
> Could you sanity check this one please. It's in the category of very
> risky of both Nikolaus and I have missed something!

It's the same as this:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/iio/industrialio-core.c?id=171c0091837c81ed5c949fec6966bb5afff2d1cf

Should be OK.

Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>

> 
> Thanks,
> 
> Jonathan
>>
>> Jonathan
>>> ---
>>>  drivers/iio/industrialio-core.c | 7 +++----
>>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
>>> index d18ded4..3ff91e0 100644
>>> --- a/drivers/iio/industrialio-core.c
>>> +++ b/drivers/iio/industrialio-core.c
>>> @@ -610,10 +610,9 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
>>>  		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
>>>  		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>>>  	case IIO_VAL_FRACTIONAL_LOG2:
>>> -		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
>>> -		tmp1 = do_div(tmp, 1000000000LL);
>>> -		tmp0 = tmp;
>>> -		return snprintf(buf, len, "%d.%09u", tmp0, tmp1);
>>> +		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
>>> +		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
>>> +		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>>>  	case IIO_VAL_INT_MULTIPLE:
>>>  	{
>>>  		int i;
>>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

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#1614694

FromJonathan Cameron <jic23@kernel.org>
Date2017-04-02 12:20 +0200
Message-ID<trKM2-7yR-13@gated-at.bofh.it>
In reply to#1614691
On 02/04/17 11:09, Lars-Peter Clausen wrote:
> On 04/02/2017 11:26 AM, Jonathan Cameron wrote:
>> On 25/03/17 18:03, Jonathan Cameron wrote:
>>> On 24/03/17 12:41, Nikolaus Schulz wrote:
>>>> Fix formatting of negative values of type IIO_VAL_FRACTIONAL_LOG2 by
>>>> switching from do_div(), which can't handle negative numbers, to
>>>> div_s64_rem().  Also use shift_right for shifting, which is safe with
>>>> negative values.
>>>>
>>>> Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
>>>> Cc: stable@vger.kernel.org
>>> Looks sane to me, but I'd like to give others time to comment on this
>>> just in case there is some odd condition neither of us has thought of!
>>>
>>> Give me a poke if we get nothing else for a few weeks.
>> Lars, I think this might have been your magic in the first place.
>>
>> Could you sanity check this one please. It's in the category of very
>> risky of both Nikolaus and I have missed something!
> 
> It's the same as this:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/iio/industrialio-core.c?id=171c0091837c81ed5c949fec6966bb5afff2d1cf
> 
> Should be OK.
> 
> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Good point.  I'd not thought to check and had forgotten that one.

Applied to the fixes-togreg branch.  Thanks,

Jonathan
> 
>>
>> Thanks,
>>
>> Jonathan
>>>
>>> Jonathan
>>>> ---
>>>>  drivers/iio/industrialio-core.c | 7 +++----
>>>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
>>>> index d18ded4..3ff91e0 100644
>>>> --- a/drivers/iio/industrialio-core.c
>>>> +++ b/drivers/iio/industrialio-core.c
>>>> @@ -610,10 +610,9 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
>>>>  		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
>>>>  		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>>>>  	case IIO_VAL_FRACTIONAL_LOG2:
>>>> -		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
>>>> -		tmp1 = do_div(tmp, 1000000000LL);
>>>> -		tmp0 = tmp;
>>>> -		return snprintf(buf, len, "%d.%09u", tmp0, tmp1);
>>>> +		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
>>>> +		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
>>>> +		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>>>>  	case IIO_VAL_INT_MULTIPLE:
>>>>  	{
>>>>  		int i;
>>>>
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>

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