From: Sinan Kaya <okaya@codeaurora.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: linux-scsi <linux-scsi@vger.kernel.org>,
timur@codeaurora.org, cov@codeaurora.org, jcm@redhat.com,
Doug Gilbert <dgilbert@interlog.com>,
"James E.J. Bottomley" <JBottomley@odin.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/4] scsi: fix compiler warning for sg
Date: Sun, 8 Nov 2015 20:17:39 -0500 [thread overview]
Message-ID: <563FF433.8000308@codeaurora.org> (raw)
In-Reply-To: <CAHp75VdaeGZ-cD6j4cUc_wdGnGYN2_x6vqua3Xrt2Fi8MGH+tQ@mail.gmail.com>
On 11/5/2015 2:56 PM, Andy Shevchenko wrote:
> On Thu, Nov 5, 2015 at 9:31 PM, Andy Shevchenko
> <andy.shevchenko@gmail.com> wrote:
>> On Thu, Nov 5, 2015 at 8:32 PM, Sinan Kaya <okaya@codeaurora.org> wrote:
>>> On 11/5/2015 1:07 PM, Andy Shevchenko wrote:
>>
>>> Let's try again.
>>>
>>> static inline u64 mult_frac64(u64 x, u32 numer, u32 denom) {
>>> u64 rem = x % denom;
>>> u64 quot = do_div(x, denom);
>>> u64 mul = rem * numer;
>>>
>>> return (quot * numer) + do_div(mul, denom);
>>> }
>>
>> First of all why not to put this to generic header? We have math64.h
>> and kernel.h.
>> Might be a good idea (needs to check current users) to move mult_frac
>> to math64.h.
>>
>> Then, x % y is already a problem. After all, you seems messed quot and
>> remainder.
>>
>> What about something like
>>
>> #if BITS_PER_LONG == 64
>>
>> #define mult_frac64(x,n,d) mult_frac(x,n,d)
>>
>> #else
>>
>> static inline u64 mult_frac64(u64 x, u32 numer, u32 denom) {
>> u64 r1 = do_div(x, denom);
>> u64 r2 = r1 * numer;
>>
>> do_div(r2, denom);
>> return (x * numer) + r2;
>> }
I'll use this instead. This is cleaner, scalable and functionally
correct to the original code. I'll post a patch with this soon.
>>
>> #endif
>>
>> ?
>
> One more look to the users of MULDIV.
>
> They all seems 32 bit for x.
> It means you don't need two do_div()s at all.
>
> Just do something like:
>
> u64 d = x * numer;
> do_div(d, denom);
> return d;
>
--
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project
next prev parent reply other threads:[~2015-11-09 1:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-05 4:46 [PATCH 1/4] scsi: mpt2sas: try 64 bit DMA when 32 bit DMA fails Sinan Kaya
2015-11-05 4:46 ` [PATCH 2/4] scsi: mpt3sas: " Sinan Kaya
2015-11-05 4:46 ` [PATCH 3/4] scsi: fix compiler warning for sg Sinan Kaya
2015-11-05 5:39 ` kbuild test robot
2015-11-05 6:40 ` kbuild test robot
2015-11-05 6:51 ` kbuild test robot
2015-11-05 8:48 ` Andy Shevchenko
2015-11-05 15:10 ` Sinan Kaya
2015-11-05 15:25 ` Timur Tabi
2015-11-05 18:07 ` Andy Shevchenko
2015-11-05 18:32 ` Sinan Kaya
2015-11-05 19:31 ` Andy Shevchenko
2015-11-05 19:56 ` Andy Shevchenko
2015-11-05 20:16 ` Sinan Kaya
2015-11-09 1:17 ` Sinan Kaya [this message]
2015-11-05 4:46 ` [PATCH 4/4] scsi: mptxsas: offload IRQ execution Sinan Kaya
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