From: Lars-Peter Clausen <lars@metafoo.de>
To: Jonathan Cameron <jic23@kernel.org>,
Gregor Boirie <gregor.boirie@parrot.com>,
<linux-iio@vger.kernel.org>
Cc: Hartmut Knaack <knaack.h@gmx.de>,
Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Subject: Re: [PATCH v1 1/1] iio:core: fix IIO_VAL_FRACTIONAL sign handling
Date: Mon, 5 Sep 2016 01:59:08 -0600 [thread overview]
Message-ID: <32c015f4-bbd7-e2f4-3b4c-f7799ea95360@metafoo.de> (raw)
In-Reply-To: <e20dc6d8-7bd0-0feb-6464-a8af61b880a9@kernel.org>
On 09/03/2016 05:13 PM, Jonathan Cameron wrote:
> On 02/09/16 19:27, Gregor Boirie wrote:
>> 7985e7c100 ("iio: Introduce a new fractional value type") introduced a
>> new IIO_VAL_FRACTIONAL value type meant to represent rational type numbers
>> expressed by a numerator and denominator combination.
>>
>> Formating of IIO_VAL_FRACTIONAL values relies upon do_div() usage. This
>> fails handling negative values properly since parameters are reevaluated
>> as unsigned values.
>> Fix this by using div_s64_rem() instead. Computed integer part will carry
>> properly signed value. Formatted fractional part will always be positive.
>>
>> Fixes: 7985e7c100 ("iio: Introduce a new fractional value type")
>> Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
>
> Hi Gregor,
>
> While this looks sensible to me, I always gain an almighty headache when
> I hit the various divide functions.
>
> Lars, the fractional code was yours in the first place.
> If you have time can you sanity check this please.
Looks good. While looking into this I noticed that we have a very similar
patch[1] in our tree, seems like somebody forgot to send that upstream.
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
[1]
https://github.com/analogdevicesinc/linux/commit/1dbcdcfd0c8d3f5513572697685d9f30ba49d851
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next prev parent reply other threads:[~2016-09-08 8:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-02 18:27 [PATCH v1 1/1] iio:core: fix IIO_VAL_FRACTIONAL sign handling Gregor Boirie
2016-09-03 15:13 ` Jonathan Cameron
2016-09-04 16:11 ` Gregor Boirie
2016-09-04 16:23 ` Jonathan Cameron
2016-09-05 7:59 ` Lars-Peter Clausen [this message]
2016-09-05 20:24 ` Jonathan Cameron
2016-09-07 18:11 ` Gregor Boirie
2016-09-07 18:54 ` Lars-Peter Clausen
2016-09-08 8:21 ` Gregor Boirie
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