Date: Sat, 14 May 2016 23:24:07 -0700 From: Adrian Chadd <adrian@freebsd.org> To: cem@freebsd.org Cc: "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r299751 - head/sys/dev/bwn Message-ID: <CAJ-Vmon=qHF1douGSVd75Z7vAumAYCZOB-VcFxMum9tUk63URg@mail.gmail.com> In-Reply-To: <CAG6CVpXZgaykWX54nUnp2UVPqGj=fnS0sMc9adAdT1FH8rZEhw@mail.gmail.com> References: <201605141952.u4EJq4jP017501@repo.freebsd.org> <CAG6CVpXZgaykWX54nUnp2UVPqGj=fnS0sMc9adAdT1FH8rZEhw@mail.gmail.com>
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On 14 May 2016 at 18:33, Conrad Meyer <cem@freebsd.org> wrote: > On Sat, May 14, 2016 at 12:52 PM, Adrian Chadd <adrian@freebsd.org> wrote: >> Author: adrian >> Date: Sat May 14 19:52:04 2016 >> New Revision: 299751 >> URL: https://svnweb.freebsd.org/changeset/base/299751 >> >> Log: >> [bwn] migrate sqrt and add another couple of util routines. >> >> ... >> >> +unsigned int >> +bwn_sqrt(struct bwn_mac *mac, unsigned int x) >> +{ >> + /* Table holding (10 * sqrt(x)) for x between 1 and 256. */ >> + static uint8_t sqrt_table[256] = { >> + 10, 14, 17, 20, 22, 24, 26, 28, >> ... >> + }; >> + >> + if (x == 0) >> + return (0); >> + if (x >= 256) { >> + unsigned int tmp; >> + >> + for (tmp = 0; x >= (2 * tmp) + 1; x -= (2 * tmp++) + 1) >> + /* do nothing */ ; >> + return (tmp); > > Does this approximation method have a name? "whatever the broadcom driver requires". >> + } >> + return (sqrt_table[x - 1] / 10); > > Why do we store the table as 10*sqrt() if we're just going to divide > every entry by ten? no idea, I just shuffled the code around so newer PHY code can use it! -a
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