cregit-Linux how code gets into the kernel

Release 4.18 lib/rational.c

Directory: lib
// SPDX-License-Identifier: GPL-2.0
/*
 * rational fractions
 *
 * Copyright (C) 2009 emlix GmbH, Oskar Schirmer <oskar@scara.com>
 *
 * helper functions when coping with rational numbers
 */

#include <linux/rational.h>
#include <linux/compiler.h>
#include <linux/export.h>

/*
 * calculate best rational approximation for a given fraction
 * taking into account restricted register size, e.g. to find
 * appropriate values for a pll with 5 bit denominator and
 * 8 bit numerator register fields, trying to set up with a
 * frequency ratio of 3.1415, one would say:
 *
 * rational_best_approximation(31415, 10000,
 *              (1 << 8) - 1, (1 << 5) - 1, &n, &d);
 *
 * you may look at given_numerator as a fixed point number,
 * with the fractional part size described in given_denominator.
 *
 * for theoretical background, see:
 * http://en.wikipedia.org/wiki/Continued_fraction
 */


void rational_best_approximation( unsigned long given_numerator, unsigned long given_denominator, unsigned long max_numerator, unsigned long max_denominator, unsigned long *best_numerator, unsigned long *best_denominator) { unsigned long n, d, n0, d0, n1, d1; n = given_numerator; d = given_denominator; n0 = d1 = 0; n1 = d0 = 1; for (;;) { unsigned long t, a; if ((n1 > max_numerator) || (d1 > max_denominator)) { n1 = n0; d1 = d0; break; } if (d == 0) break; t = d; a = n / d; d = n % d; n = t; t = n0 + a * n1; n0 = n1; n1 = t; t = d0 + a * d1; d0 = d1; d1 = t; } *best_numerator = n1; *best_denominator = d1; }

Contributors

PersonTokensPropCommitsCommitProp
Oskar Schirmer172100.00%1100.00%
Total172100.00%1100.00%

EXPORT_SYMBOL(rational_best_approximation);

Overall Contributors

PersonTokensPropCommitsCommitProp
Oskar Schirmer18296.30%240.00%
Paul Gortmaker42.12%120.00%
Sascha Hauer21.06%120.00%
Greg Kroah-Hartman10.53%120.00%
Total189100.00%5100.00%
Directory: lib
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