Messages in this thread | | | Subject | Re: [PATCH 3/4] scsi: fix compiler warning for sg | From | Sinan Kaya <> | Date | Thu, 5 Nov 2015 10:10:56 -0500 |
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On 11/5/2015 3:48 AM, Andy Shevchenko wrote: > 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; > } >
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; }
#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 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > >
-- 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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