Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162133AbbKESHG (ORCPT ); Thu, 5 Nov 2015 13:07:06 -0500 Received: from mail-yk0-f170.google.com ([209.85.160.170]:35171 "EHLO mail-yk0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162123AbbKESHE (ORCPT ); Thu, 5 Nov 2015 13:07:04 -0500 MIME-Version: 1.0 In-Reply-To: <563B7180.2000405@codeaurora.org> References: <1446698789-19308-1-git-send-email-okaya@codeaurora.org> <1446698789-19308-3-git-send-email-okaya@codeaurora.org> <563B7180.2000405@codeaurora.org> Date: Thu, 5 Nov 2015 20:07:03 +0200 Message-ID: Subject: Re: [PATCH 3/4] scsi: fix compiler warning for sg From: Andy Shevchenko To: Sinan Kaya Cc: linux-scsi , timur@codeaurora.org, cov@codeaurora.org, jcm@redhat.com, Doug Gilbert , "James E.J. Bottomley" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3074 Lines: 110 On Thu, Nov 5, 2015 at 5:10 PM, Sinan Kaya wrote: > > > On 11/5/2015 3:48 AM, Andy Shevchenko wrote: >> >> On Thu, Nov 5, 2015 at 6:46 AM, Sinan Kaya 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 >>> --- >>> 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 >>> >>> -- >>> 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 -- With Best Regards, Andy Shevchenko -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/