+/* 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 _TOOLS_LINUX_LOG2_H
-#define _TOOLS_LINUX_LOG2_H
-
-#include <limits.h>
-#ifndef PAGE_SHIFT
-#define PAGE_SHIFT ilog2(PAGE_SIZE)
-#endif
+#ifndef _LINUX_LOG2_H
+#define _LINUX_LOG2_H
+#include <linux/types.h>
#include <linux/bitops.h>
-#include <linux/compiler.h>
-
-/*
- * deal with unrepresentable constant logarithms
- */
-extern __attribute__((const))
-int ____ilog2_NaN(void);
/*
* non-constant log of base 2 calculators
* more efficiently than using fls() and fls64()
* - the arch is not required to handle n==0 if implementing the fallback
*/
+#ifndef CONFIG_ARCH_HAS_ILOG2_U32
static inline __attribute__((const))
int __ilog2_u32(u32 n)
{
return fls(n) - 1;
}
+#endif
+#ifndef CONFIG_ARCH_HAS_ILOG2_U64
static inline __attribute__((const))
int __ilog2_u64(u64 n)
{
return fls64(n) - 1;
}
+#endif
-/*
- * Determine whether some value is a power of two, where zero is
+/**
+ * is_power_of_2() - check if a value is a power of two
+ * @n: the value to check
+ *
+ * Determine whether some value is a power of two, where zero is
* *not* considered a power of two.
+ * Return: true if @n is a power of 2, otherwise false.
*/
-
static inline __attribute__((const))
bool is_power_of_2(unsigned long n)
{
return (n != 0 && ((n & (n - 1)) == 0));
}
-/*
- * round up to nearest power of two
+/**
+ * __roundup_pow_of_two() - round up to nearest power of two
+ * @n: value to round up
*/
static inline __attribute__((const))
unsigned long __roundup_pow_of_two(unsigned long n)
return 1UL << fls_long(n - 1);
}
-/*
- * round down to nearest power of two
+/**
+ * __rounddown_pow_of_two() - round down to nearest power of two
+ * @n: value to round down
*/
static inline __attribute__((const))
unsigned long __rounddown_pow_of_two(unsigned long n)
}
/**
- * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
- * @n - parameter
- *
- * constant-capable log of base 2 calculation
- * - this can be used to initialise global variables from constant data, hence
- * the massive ternary operator construction
+ * const_ilog2 - log base 2 of 32-bit or a 64-bit constant unsigned value
+ * @n: parameter
*
- * selects the appropriately-sized optimised version depending on sizeof(n)
+ * Use this where sparse expects a true constant expression, e.g. for array
+ * indices.
*/
-#define ilog2(n) \
+#define const_ilog2(n) \
( \
__builtin_constant_p(n) ? ( \
- (n) < 1 ? ____ilog2_NaN() : \
+ (n) < 2 ? 0 : \
(n) & (1ULL << 63) ? 63 : \
(n) & (1ULL << 62) ? 62 : \
(n) & (1ULL << 61) ? 61 : \
(n) & (1ULL << 4) ? 4 : \
(n) & (1ULL << 3) ? 3 : \
(n) & (1ULL << 2) ? 2 : \
- (n) & (1ULL << 1) ? 1 : \
- (n) & (1ULL << 0) ? 0 : \
- ____ilog2_NaN() \
- ) : \
- (sizeof(n) <= 4) ? \
- __ilog2_u32(n) : \
- __ilog2_u64(n) \
+ 1) : \
+ -1)
+
+/**
+ * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value
+ * @n: parameter
+ *
+ * constant-capable log of base 2 calculation
+ * - this can be used to initialise global variables from constant data, hence
+ * the massive ternary operator construction
+ *
+ * selects the appropriately-sized optimised version depending on sizeof(n)
+ */
+#define ilog2(n) \
+( \
+ __builtin_constant_p(n) ? \
+ const_ilog2(n) : \
+ (sizeof(n) <= 4) ? \
+ __ilog2_u32(n) : \
+ __ilog2_u64(n) \
)
/**
* roundup_pow_of_two - round the given value up to nearest power of two
- * @n - parameter
+ * @n: parameter
*
* round the given value up to the nearest power of two
* - the result is undefined when n == 0
/**
* rounddown_pow_of_two - round the given value down to nearest power of two
- * @n - parameter
+ * @n: parameter
*
* round the given value down to the nearest power of two
* - the result is undefined when n == 0
__rounddown_pow_of_two(n) \
)
+static inline __attribute_const__
+int __order_base_2(unsigned long n)
+{
+ return n > 1 ? ilog2(n - 1) + 1 : 0;
+}
+
+/**
+ * order_base_2 - calculate the (rounded up) base 2 order of the argument
+ * @n: parameter
+ *
+ * The first few values calculated by this routine:
+ * ob2(0) = 0
+ * ob2(1) = 0
+ * ob2(2) = 1
+ * ob2(3) = 2
+ * ob2(4) = 2
+ * ob2(5) = 3
+ * ... and so on.
+ */
+#define order_base_2(n) \
+( \
+ __builtin_constant_p(n) ? ( \
+ ((n) == 0 || (n) == 1) ? 0 : \
+ ilog2((n) - 1) + 1) : \
+ __order_base_2(n) \
+)
+
static inline __attribute__((const))
-int __get_order(unsigned long size)
+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) \
+)
+
+/**
+ * get_order - Determine the allocation order of a memory size
+ * @size: The size for which to get the order
+ *
+ * Determine the allocation order of a particular sized block of memory. This
+ * is on a logarithmic scale, where:
+ *
+ * 0 -> 2^0 * PAGE_SIZE and below
+ * 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
+ * 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
+ * 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
+ * 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
+ * ...
+ *
+ * The order returned is used to find the smallest allocation granule required
+ * to hold an object of the specified size.
+ *
+ * The result is undefined if the size is 0.
+ */
+static inline __attribute_const__ int get_order(unsigned long size)
{
- int order;
+ if (__builtin_constant_p(size)) {
+ if (!size)
+ return BITS_PER_LONG - PAGE_SHIFT;
+
+ if (size < (1UL << PAGE_SHIFT))
+ return 0;
+
+ return ilog2((size) - 1) - PAGE_SHIFT + 1;
+ }
size--;
size >>= PAGE_SHIFT;
#if BITS_PER_LONG == 32
- order = fls(size);
+ return fls(size);
#else
- order = fls64(size);
+ return fls64(size);
#endif
- return order;
}
-#define get_order(n) \
-( \
- __builtin_constant_p(n) ? ( \
- ((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \
- (((n) < (1UL << PAGE_SHIFT)) ? 0 : \
- ilog2((n) - 1) - PAGE_SHIFT + 1) \
- ) : \
- __get_order(n) \
-)
-
-#endif /* _TOOLS_LINUX_LOG2_H */
+#endif /* _LINUX_LOG2_H */
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