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References: <YcIpAKV7Cmi0o7PU@debian-BULLSEYE-live-builder-AMD64>
In-Reply-To: <YcIpAKV7Cmi0o7PU@debian-BULLSEYE-live-builder-AMD64>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Wed, 22 Dec 2021 20:49:26 +0200
Message-ID: <CAHp75VcU8B8fydh874p6HpgGXXRYvNGdphH=i17JHB3DYJ1JZQ@mail.gmail.com>
Subject: Re: [PATCH] drivers:iio:dac make expression evaluation 64-bit
To:     Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc:     Lars-Peter Clausen <lars@metafoo.de>,
        Michael Hennerich <Michael.Hennerich@analog.com>,
        Jonathan Cameron <jic23@kernel.org>,
        Mihail Chindris <mihail.chindris@analog.com>,
        "open list:IIO SUBSYSTEM AND DRIVERS" <linux-iio@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        Collabora Kernel ML <kernel@collabora.com>,
        kernel-janitors <kernel-janitors@vger.kernel.org>
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Precedence: bulk

On Wed, Dec 22, 2021 at 5:59 PM Muhammad Usama Anjum
<usama.anjum@collabora.com> wrote:
>
> Two 32-bit values are being evaluated using 32-bit arithmetic and then
> passed to s64 type. It is wrong. Expression should be evaluated using
> 64-bit arithmetic and then passed.

...

>         dac->ch_data[ch].scale_dec = DIV_ROUND_CLOSEST((s64)rem * 1000000,
>                                                         65536);

Shouldn't the above be fixed as well? Has anybody tried to compile on
32-bit arch this?

> -       dac->ch_data[ch].offset_int = div_s64_rem(v_min * 65536, span, &rem);
> +       dac->ch_data[ch].offset_int = div_s64_rem(v_min * 65536L, span, &rem);
>         tmp = (s64)rem * 1000000;
>         dac->ch_data[ch].offset_dec = div_s64(tmp, span);
>  }

-- 
With Best Regards,
Andy Shevchenko