Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754968AbdLTJ4i (ORCPT ); Wed, 20 Dec 2017 04:56:38 -0500 Received: from smtprelay0113.hostedemail.com ([216.40.44.113]:38401 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754643AbdLTJ4c (ORCPT ); Wed, 20 Dec 2017 04:56:32 -0500 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,joe@perches.com,:::::::::::::::::::::::::::::,RULES_HIT:41:355:379:541:599:960:988:989:1260:1277:1311:1313:1314:1345:1359:1373:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2393:2559:2562:2828:3138:3139:3140:3141:3142:3353:3622:3865:3866:3867:3870:3871:4321:5007:6117:6119:6742:7875:7903:7904:10004:10400:10848:11026:11232:11473:11658:11914:12296:12438:12740:12760:12895:13069:13311:13357:13439:14659:14721:21080:21433:21627:30054:30091,0,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: shelf37_72cbc981d1911 X-Filterd-Recvd-Size: 2716 Message-ID: <1513763787.1234.102.camel@perches.com> Subject: Re: [PATCH v9 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: Wed, 20 Dec 2017 01:56:27 -0800 In-Reply-To: <20171220093315.25311-1-cmo@melexis.com> References: <20171220093315.25311-1-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 Content-Length: 1432 Lines: 65 On Wed, 2017-12-20 at 10:33 +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. [] > diff --git a/include/linux/kernel.h b/include/linux/kernel.h [] > @@ -459,6 +459,7 @@ extern int kernel_text_address(unsigned long addr); > extern int func_ptr_is_kernel_text(void *ptr); > > unsigned long int_sqrt(unsigned long); > +u32 int_sqrt64(u64 x); #ifdef BITS_PER_LONG == 64 static inline u32 int_sqrt64(u64 x) { re turn (u32)int_sqrt(x); } #else u32 int_sqrt64(u64 x); #endif [] > +#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 << (fls64(x) & ~1ULL); > + while (m != 0) { > + b = y + m; > + y >>= 1; > + > + if (x >= b) { > + x -= b; > + y += m; > + } > + m >>= 2; > + } > + > + return y; > +} > +EXPORT_SYMBOL(int_sqrt64); > +#else > +u32 int_sqrt64(u64 x) > +{ > + return int_sqrt(x); > +} > +EXPORT_SYMBOL(int_sqrt64); > +#endif This doesn't need to be EXPORT_SYMBOL for the BITS_PER_LONG == 64 case