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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
5b17e1cd AB |
2 | #ifndef __ASM_GENERIC_GETORDER_H |
3 | #define __ASM_GENERIC_GETORDER_H | |
fd4fd5aa | 4 | |
fd4fd5aa SR |
5 | #ifndef __ASSEMBLY__ |
6 | ||
38f33230 | 7 | #include <linux/compiler.h> |
d66acc39 DH |
8 | #include <linux/log2.h> |
9 | ||
10 | /* | |
11 | * Runtime evaluation of get_order() | |
12 | */ | |
13 | static inline __attribute_const__ | |
14 | int __get_order(unsigned long size) | |
15 | { | |
16 | int order; | |
17 | ||
18 | size--; | |
19 | size >>= PAGE_SHIFT; | |
20 | #if BITS_PER_LONG == 32 | |
21 | order = fls(size); | |
22 | #else | |
23 | order = fls64(size); | |
24 | #endif | |
25 | return order; | |
26 | } | |
fd4fd5aa | 27 | |
e0891a98 DH |
28 | /** |
29 | * get_order - Determine the allocation order of a memory size | |
30 | * @size: The size for which to get the order | |
31 | * | |
32 | * Determine the allocation order of a particular sized block of memory. This | |
33 | * is on a logarithmic scale, where: | |
34 | * | |
35 | * 0 -> 2^0 * PAGE_SIZE and below | |
36 | * 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1 | |
37 | * 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1 | |
38 | * 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1 | |
39 | * 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1 | |
40 | * ... | |
41 | * | |
42 | * The order returned is used to find the smallest allocation granule required | |
43 | * to hold an object of the specified size. | |
44 | * | |
45 | * The result is undefined if the size is 0. | |
46 | * | |
47 | * This function may be used to initialise variables with compile time | |
48 | * evaluations of constants. | |
49 | */ | |
d66acc39 DH |
50 | #define get_order(n) \ |
51 | ( \ | |
52 | __builtin_constant_p(n) ? ( \ | |
b893485d JR |
53 | ((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \ |
54 | (((n) < (1UL << PAGE_SHIFT)) ? 0 : \ | |
d66acc39 DH |
55 | ilog2((n) - 1) - PAGE_SHIFT + 1) \ |
56 | ) : \ | |
57 | __get_order(n) \ | |
58 | ) | |
fd4fd5aa SR |
59 | |
60 | #endif /* __ASSEMBLY__ */ | |
fd4fd5aa | 61 | |
5b17e1cd | 62 | #endif /* __ASM_GENERIC_GETORDER_H */ |