From: Luca Coelho <luca@coelho.fi>
To: Nick Desaulniers <ndesaulniers@google.com>,
Nathan Chancellor <natechancellor@gmail.com>
Cc: Johannes Berg <johannes.berg@intel.com>,
Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
Intel Linux Wireless <linuxwifi@intel.com>,
Kalle Valo <kvalo@codeaurora.org>,
linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iwlwifi: mvm: Use div64_s64 instead of do_div in iwl_mvm_debug_range_resp
Date: Wed, 20 Feb 2019 11:39:54 +0200 [thread overview]
Message-ID: <cd93696bcca66944ec2d472758d86e8f7c6e81de.camel@coelho.fi> (raw)
In-Reply-To: <CAKwvOdmFE0kQoxvRDcarT+kYLXxqKYJfVHo4uTiYm7-wDefrrw@mail.gmail.com>
On Tue, 2019-02-19 at 11:05 -0800, Nick Desaulniers wrote:
> On Tue, Feb 19, 2019 at 10:21 AM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> > Clang warns:
> >
> > drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c:465:2:
> > warning:
> > comparison of distinct pointer types ('typeof ((rtt_avg)) *' (aka
> > 'long
> > long *') and 'uint64_t *' (aka 'unsigned long long *'))
> > [-Wcompare-distinct-pointer-types]
> > do_div(rtt_avg, 6666);
> > ^~~~~~~~~~~~~~~~~~~~~
> > include/asm-generic/div64.h:222:28: note: expanded from macro
> > 'do_div'
> > (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
> > ~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
> > 1 warning generated.
> >
> > do_div expects an unsigned dividend. Use div64_s64, which expects a
> > signed dividend.
>
> Eh, IIRC, signed vs unsigned division has implications for rounding
> towards zero or not, but I doubt that the round trip time average
> (RTT
> avg) should ever be negative. General rule of thumb for C is to keep
> arithmetic signed (even when working with non zero values), so rather
> than make the literal (6666) a unsigned long, I agree with your
> change
> to keep the division signed as well. Thanks for the fix.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Thanks for the patch and for the review. I've applied this to our
internal tree and it will be sent upstreaming following our normal
upstreaming process.
--
Cheers,
Luca.
next prev parent reply other threads:[~2019-02-20 9:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-19 18:21 [PATCH] iwlwifi: mvm: Use div64_s64 instead of do_div in iwl_mvm_debug_range_resp Nathan Chancellor
2019-02-19 19:05 ` Nick Desaulniers
2019-02-20 9:39 ` Luca Coelho [this message]
2019-02-20 10:51 ` Arnd Bergmann
2019-02-20 17:56 ` Nathan Chancellor
2019-02-21 7:33 ` Luciano Coelho
2019-02-21 8:06 ` [PATCH v2] iwlwifi: mvm: Use div_s64 " Nathan Chancellor
2019-02-22 0:13 ` Nick Desaulniers
2019-02-22 7:45 ` Luciano Coelho
2019-02-22 8:52 ` Arnd Bergmann
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