On Thu, Nov 5, 2015 at 5:10 PM, Sinan Kaya <okaya@xxxxxxxxxxxxxx> wrote:
>
>
> On 11/5/2015 3:48 AM, Andy Shevchenko wrote:
>>
>> On Thu, Nov 5, 2015 at 6:46 AM, Sinan Kaya <okaya@xxxxxxxxxxxxxx> wrote:
>>>
>>> The MULDIV macro has been designed for small
>>> numbers. It emits an overflow warning on 64 bit
>>> systems. This patch places type casts in the
>>> parameters to fix the compiler warning.
>>>
>>> Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
>>> ---
>>> drivers/scsi/sg.c | 5 ++++-
>>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
>>> index 9d7b7db..eb2739d 100644
>>> --- a/drivers/scsi/sg.c
>>> +++ b/drivers/scsi/sg.c
>>> @@ -88,7 +88,10 @@ static void sg_proc_cleanup(void);
>>> * Of course an overflow is inavoidable if the result of muldiv doesn't
>>> fit
>>> * in 32 bits.
>>> */
>>> -#define MULDIV(X,MUL,DIV) ((((X % DIV) * MUL) / DIV) + ((X / DIV) *
>>> MUL))
>>> +static inline u64 MULDIV(u64 X, u32 MUL, u32 DIV)
>>> +{
>>> + return ((((X % DIV) * MUL) / DIV) + ((X / DIV) * MUL));
>>> +}
>>
>>
>> Like kbuild bot already told you it would be nice to think of 32-bit
>> architectures.
>>
>> Moreover we have mult_frac() macro already for 32-bit numbers.
>>
>> For 64 bit numbers you need to do do_div().
>>
>> Like:
>>
>> static inline u64 mult_frac64(u64 x, u32 m, u32 n)
>> {
>> u64 ret;
>>
>> ret = do_div(x, n);
>> return ret * m;
>> }
>>
>
> 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.
>
> #define MULDIV(X,MUL,DIV) mult_frac64(X, MUL, DIV)
>
>>
>>>
>>> #define SG_DEFAULT_TIMEOUT MULDIV(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ)
>>>
>>> --
>>> 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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>>
>>
>>
>>
>
> --
> 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
--
With Best Regards,
Andy Shevchenko
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