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

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On Thu, Nov 5, 2015 at 6:46 AM, Sinan Kaya <okaya@codeaurora.org> 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@codeaurora.org>
> ---
>  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;
}


>
>  #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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-- 
With Best Regards,
Andy Shevchenko
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[PATCH 3/4] scsi: fix compiler warning for sg Sinan Kaya <okaya@codeaurora.org> - 2015-11-05 05:50 +0100
  Re: [PATCH 3/4] scsi: fix compiler warning for sg kbuild test robot <lkp@intel.com> - 2015-11-05 06:50 +0100
  Re: [PATCH 3/4] scsi: fix compiler warning for sg kbuild test robot <lkp@intel.com> - 2015-11-05 08:00 +0100
  Re: [PATCH 3/4] scsi: fix compiler warning for sg kbuild test robot <lkp@intel.com> - 2015-11-05 08:10 +0100
  Re: [PATCH 3/4] scsi: fix compiler warning for sg Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-05 09:50 +0100
    Re: [PATCH 3/4] scsi: fix compiler warning for sg Sinan Kaya <okaya@codeaurora.org> - 2015-11-05 16:20 +0100
      Re: [PATCH 3/4] scsi: fix compiler warning for sg Timur Tabi <timur@codeaurora.org> - 2015-11-05 16:30 +0100
      Re: [PATCH 3/4] scsi: fix compiler warning for sg Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-05 19:10 +0100
        Re: [PATCH 3/4] scsi: fix compiler warning for sg Sinan Kaya <okaya@codeaurora.org> - 2015-11-05 19:40 +0100
          Re: [PATCH 3/4] scsi: fix compiler warning for sg Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-05 20:40 +0100
            Re: [PATCH 3/4] scsi: fix compiler warning for sg Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-05 21:00 +0100
              Re: [PATCH 3/4] scsi: fix compiler warning for sg Sinan Kaya <okaya@codeaurora.org> - 2015-11-05 21:20 +0100
              Re: [PATCH 3/4] scsi: fix compiler warning for sg Sinan Kaya <okaya@codeaurora.org> - 2015-11-09 02:20 +0100

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