reciprocal_div.c 528 Bytes
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/kernel.h>
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#include <asm/div64.h>
#include <linux/reciprocal_div.h>
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#include <linux/export.h>
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/*
 * For a description of the algorithm please have a look at
 * include/linux/reciprocal_div.h
 */

struct reciprocal_value reciprocal_value(u32 d)
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{
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	struct reciprocal_value R;
	u64 m;
	int l;

	l = fls(d - 1);
	m = ((1ULL << 32) * ((1ULL << l) - d));
	do_div(m, d);
	++m;
	R.m = (u32)m;
	R.sh1 = min(l, 1);
	R.sh2 = max(l - 1, 0);

	return R;
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}
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EXPORT_SYMBOL(reciprocal_value);