diff options
Diffstat (limited to 'include/linux/log2.h')
| -rw-r--r-- | include/linux/log2.h | 40 |
1 files changed, 35 insertions, 5 deletions
diff --git a/include/linux/log2.h b/include/linux/log2.h index 2af7f77866d0..83a4a3ca3e8a 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -1,12 +1,8 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ /* Integer base 2 logarithm calculation * * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License - * as published by the Free Software Foundation; either version - * 2 of the License, or (at your option) any later version. */ #ifndef _LINUX_LOG2_H @@ -224,4 +220,38 @@ int __order_base_2(unsigned long n) ilog2((n) - 1) + 1) : \ __order_base_2(n) \ ) + +static inline __attribute__((const)) +int __bits_per(unsigned long n) +{ + if (n < 2) + return 1; + if (is_power_of_2(n)) + return order_base_2(n) + 1; + return order_base_2(n); +} + +/** + * bits_per - calculate the number of bits required for the argument + * @n: parameter + * + * This is constant-capable and can be used for compile time + * initializations, e.g bitfields. + * + * The first few values calculated by this routine: + * bf(0) = 1 + * bf(1) = 1 + * bf(2) = 2 + * bf(3) = 2 + * bf(4) = 3 + * ... and so on. + */ +#define bits_per(n) \ +( \ + __builtin_constant_p(n) ? ( \ + ((n) == 0 || (n) == 1) \ + ? 1 : ilog2(n) + 1 \ + ) : \ + __bits_per(n) \ +) #endif /* _LINUX_LOG2_H */ |