From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Meerwald Subject: Re: [PATCH 1/2] lib: int_sqrt: add int64_sqrt routine Date: Mon, 23 Jun 2014 11:52:56 +0200 (CEST) Message-ID: References: <1403516581-12560-1-git-send-email-21cnbao@gmail.com> <1403516581-12560-2-git-send-email-21cnbao@gmail.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: Received: from ns.pmeerw.net ([87.118.82.44]:44162 "EHLO pmeerw.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752441AbaFWJxB (ORCPT ); Mon, 23 Jun 2014 05:53:01 -0400 In-Reply-To: <1403516581-12560-2-git-send-email-21cnbao@gmail.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Barry Song <21cnbao@gmail.com> Cc: dmitry.torokhov@gmail.com, dtor@mail.ru, akpm@linux-foundation.org, linux-input@vger.kernel.org, workgroup.linux@csr.com, Yibo Cai , Barry Song > Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC > touchscreen driver needs it. maybe the code could be #MACRO()'d to avoid duplication see comment below > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index 4c52907..6e63081 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -418,6 +418,7 @@ struct pid; > extern struct pid *session_of_pgrp(struct pid *pgrp); > > unsigned long int_sqrt(unsigned long); > +unsigned long long int64_sqrt(unsigned long long); > > extern void bust_spinlocks(int yes); > extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */ > diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c > index 1ef4cc3..2aa9fcc 100644 > --- a/lib/int_sqrt.c > +++ b/lib/int_sqrt.c > @@ -36,3 +36,30 @@ unsigned long int_sqrt(unsigned long x) > return y; > } > EXPORT_SYMBOL(int_sqrt); > + > +/* > + * Square root of a 64-bit digit. > + * Same as int_sqrt on 64-bit platforms where "long" equals "long long" > + */ > +unsigned long long int64_sqrt(unsigned long long x) > +{ > + unsigned long long m = 0, y = 0, b = 0; initialization for b, m not needed the original int_sqrt() code correctly skips initialization > + > + if (x <= 1) > + return x; > + > + m = 1ULL << (BITS_PER_LONG_LONG - 2); > + while (m != 0) { > + b = y + m; > + y >>= 1; > + > + if (x >= b) { > + x -= b; > + y += m; > + } > + m >>= 2; > + } > + > + return y; > +} > +EXPORT_SYMBOL(int64_sqrt); > -- Peter Meerwald +43-664-2444418 (mobile)