linux-kernel - Re: [PATCH 3/4] scsi: fix compiler warning for sg

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Date:	Thu, 5 Nov 2015 13:32:19 -0500
From:	Sinan Kaya <okaya@...eaurora.org>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	linux-scsi <linux-scsi@...r.kernel.org>, timur@...eaurora.org,
	cov@...eaurora.org, jcm@...hat.com,
	Doug Gilbert <dgilbert@...erlog.com>,
	"James E.J. Bottomley" <JBottomley@...n.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] scsi: fix compiler warning for sg



On 11/5/2015 1:07 PM, Andy Shevchenko wrote:
>> OK, I didn't know that we had such a macro. To make this look like the other
>> >macro, I can do this.
>> >
>> >static inline u64 mult_frac64(u64 x, u32 numer, u32 denom)
>> >{
>> >         u64 quot;
>> >         u64 rem  = x % denom;
>> >         u64 rem2;
>> >
>> >         quot = x;
>> >         do_div(quot, denom);
>> >
>> >         rem2 = rem * numer;
>> >         do_div(rem2, denom);
>> >
>> >         return (quot * numer) + rem2;
>> >}
> Might be I did a wrong smaple, but do_div() returns two values actually.
> You perhaps overlooked it and thus wrote something redundant above.
>

OK, I was looking at example usages in the kernel. The ones I looked 
always used the first argument as an input & output parameter. I got 
nervous about overwriting something.

void __ndelay(unsigned long long nsecs)
{
	u64 end;

	nsecs <<= 9;
	do_div(nsecs, 125);
...
}

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);
}

I'll do a s/MULDIV/mult_frac64/g to address Timur's concern.

-- 
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
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