From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751829AbdLSQKC (ORCPT ); Tue, 19 Dec 2017 11:10:02 -0500 Received: from smtprelay0226.hostedemail.com ([216.40.44.226]:50787 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751171AbdLSQJ7 (ORCPT ); Tue, 19 Dec 2017 11:09:59 -0500 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,joe@perches.com,:::::::::::::::::::::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1373:1437:1515:1516:1518:1534:1542:1593:1594:1711:1730:1747:1777:1792:2393:2559:2562:2828:3138:3139:3140:3141:3142:3354:3622:3865:3866:3867:3870:3871:3873:4321:4605:5007:6117:6119:6742:7875:7903:7904:10004:10400:10848:11026:11232:11473:11658:11914:12043:12291:12296:12438:12555:12683:12740:12760:12895:12986:13161:13229:13439:14181:14659:14721:21080:21433:21451:21627:30054:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:1,LUA_SUMMARY:none X-HE-Tag: spade97_73aa142644e5b X-Filterd-Recvd-Size: 3243 Message-ID: <1513699793.1234.41.camel@perches.com> Subject: Re: [PATCH v7 1/3] lib: Add strongly typed 64bit int_sqrt From: Joe Perches To: Crt Mori , Jonathan Cameron Cc: Ingo Molnar , Andrew Morton , Kees Cook , Rusty Russell , Ian Abbott , Larry Finger , Niklas Soderlund , Thomas Gleixner , Krzysztof Kozlowski , Masahiro Yamada , linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, Peter Zijlstra Date: Tue, 19 Dec 2017 08:09:53 -0800 In-Reply-To: <20171219155908.29528-1-cmo@melexis.com> References: <20171219155908.29528-1-cmo@melexis.com> Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.26.1-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2017-12-19 at 16:59 +0100, Crt Mori wrote: > There is no option to perform 64bit integer sqrt on 32bit platform. > Added stronger typed int_sqrt64 enables the 64bit calculations to > be performed on 32bit platforms. Although int_sqrt() is a rough > approximation, the same algorithm is used in int_sqrt64() as good > enough on 32bit platform. > > Signed-off-by: Crt Mori > --- > include/linux/kernel.h | 6 ++++++ > lib/int_sqrt.c | 32 ++++++++++++++++++++++++++++++++ > 2 files changed, 38 insertions(+) > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index 0ad4c3044cf9..f3bebd3a9213 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -459,6 +459,12 @@ extern int kernel_text_address(unsigned long addr); > extern int func_ptr_is_kernel_text(void *ptr); > > unsigned long int_sqrt(unsigned long); > +#if BITS_PER_LONG != 64 > +#define int_sqrt64 _int_sqrt64 > +u32 _int_sqrt64(u64 x); > +#else > +#define int_sqrt64 int_sqrt > +#endif As you've changed the return type for the 64-bit function to u32, there is a unsigned long / u32 return mismatch on 64 bit platforms. I suspect you need to define this as: #define int_sqrt64(x) ((u32)int_sqrt(x)) > diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c [] > @@ -36,3 +36,35 @@ unsigned long int_sqrt(unsigned long x) > return y; > } > EXPORT_SYMBOL(int_sqrt); > + > +#if BITS_PER_LONG != 64 > +/** > + * > + * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input > + * is expected. > + * @x: 64bit integer of which to calculate the sqrt > + */ > +u32 _int_sqrt64(u64 x) > +{ > + u64 b, m, y = 0; > + > + if (x <= 1) > + return x; > + > + m = 1ULL << (64 - 2); Should probably use fls64 here. > + while (m != 0) { > + b = y + m; > + y >>= 1; > + > + if (x >= b) { > + x -= b; > + y += m; > + } > + m >>= 2; > + } > + > + return y; > +} > +EXPORT_SYMBOL(_int_sqrt64); > +#endif > +