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Linux has a header file that defines an ilog2 function and some simple functions/macros that use it: roundup_pow_of_two, is_power_of_2, rounddown_pow_of_two, and order_base_2. This change moves three of those simple functions (all but is_power_of_2) from linuxkpi to libkern. It also deletes a few implementations of these functions that have previously been copied into code for various device drivers, so that they can use the libkern version. The is_power_of_2 macro was not moved because powerof2 in param.h provides almost the same service already (except that they disagree about whether 0 is a power of two). Since the linux definitions of these functions were copied into FreeBSD 11 years ago, linux has improved them, and this change provides those improvements. In particular, a giant table of log values for evaluating ilog2 for constant values is no longer necessary. Reviewed by: alc, markj (previous version) Differential Revision: https://reviews.freebsd.org/D45536 (cherry picked from commit c8b0c33b03ac072413b27bed2bdae2ae27426f3a)
41 lines
1.7 KiB
C
41 lines
1.7 KiB
C
/*-
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* Copyright (c) 2010 Isilon Systems, Inc.
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* Copyright (c) 2010 iX Systems, Inc.
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* Copyright (c) 2010 Panasas, Inc.
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* Copyright (c) 2013-2015 Mellanox Technologies, Ltd.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _LINUXKPI_LINUX_LOG2_H_
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#define _LINUXKPI_LINUX_LOG2_H_
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#include <linux/types.h>
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#include <sys/libkern.h>
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#define is_power_of_2(n) ({ \
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__typeof(n) _n = (n); \
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_n != 0 && (_n & (_n - 1)) == 0; \
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})
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#endif /* _LINUXKPI_LINUX_LOG2_H_ */
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