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153 lines · 2.6 KiB

1/*
2 * Fast C2P (Chunky-to-Planar) Conversion
3 *
4 * Copyright (C) 2003-2008 Geert Uytterhoeven
5 *
6 * NOTES:
7 * - This code was inspired by Scout's C2P tutorial
8 * - It assumes to run on a big endian system
9 *
10 * This file is subject to the terms and conditions of the GNU General Public
11 * License. See the file COPYING in the main directory of this archive
12 * for more details.
13 */
14
15#include <linux/build_bug.h>
16
17
18 /*
19 * Basic transpose step
20 */
21
22static inline void _transp(u32 d[], unsigned int i1, unsigned int i2,
23 unsigned int shift, u32 mask)
24{
25 u32 t = (d[i1] ^ (d[i2] >> shift)) & mask;
26
27 d[i1] ^= t;
28 d[i2] ^= t << shift;
29}
30
31
32static __always_inline u32 get_mask(unsigned int n)
33{
34 switch (n) {
35 case 1:
36 return 0x55555555;
37
38 case 2:
39 return 0x33333333;
40
41 case 4:
42 return 0x0f0f0f0f;
43
44 case 8:
45 return 0x00ff00ff;
46
47 case 16:
48 return 0x0000ffff;
49 }
50
51 BUILD_BUG();
52 return 0;
53}
54
55
56 /*
57 * Transpose operations on 8 32-bit words
58 */
59
60static __always_inline void transp8(u32 d[], unsigned int n, unsigned int m)
61{
62 u32 mask = get_mask(n);
63
64 switch (m) {
65 case 1:
66 /* First n x 1 block */
67 _transp(d, 0, 1, n, mask);
68 /* Second n x 1 block */
69 _transp(d, 2, 3, n, mask);
70 /* Third n x 1 block */
71 _transp(d, 4, 5, n, mask);
72 /* Fourth n x 1 block */
73 _transp(d, 6, 7, n, mask);
74 return;
75
76 case 2:
77 /* First n x 2 block */
78 _transp(d, 0, 2, n, mask);
79 _transp(d, 1, 3, n, mask);
80 /* Second n x 2 block */
81 _transp(d, 4, 6, n, mask);
82 _transp(d, 5, 7, n, mask);
83 return;
84
85 case 4:
86 /* Single n x 4 block */
87 _transp(d, 0, 4, n, mask);
88 _transp(d, 1, 5, n, mask);
89 _transp(d, 2, 6, n, mask);
90 _transp(d, 3, 7, n, mask);
91 return;
92 }
93
94 BUILD_BUG();
95}
96
97
98 /*
99 * Transpose operations on 4 32-bit words
100 */
101
102static __always_inline void transp4(u32 d[], unsigned int n, unsigned int m)
103{
104 u32 mask = get_mask(n);
105
106 switch (m) {
107 case 1:
108 /* First n x 1 block */
109 _transp(d, 0, 1, n, mask);
110 /* Second n x 1 block */
111 _transp(d, 2, 3, n, mask);
112 return;
113
114 case 2:
115 /* Single n x 2 block */
116 _transp(d, 0, 2, n, mask);
117 _transp(d, 1, 3, n, mask);
118 return;
119 }
120
121 BUILD_BUG();
122}
123
124
125 /*
126 * Transpose operations on 4 32-bit words (reverse order)
127 */
128
129static __always_inline void transp4x(u32 d[], unsigned int n, unsigned int m)
130{
131 u32 mask = get_mask(n);
132
133 switch (m) {
134 case 2:
135 /* Single n x 2 block */
136 _transp(d, 2, 0, n, mask);
137 _transp(d, 3, 1, n, mask);
138 return;
139 }
140
141 BUILD_BUG();
142}
143
144
145 /*
146 * Compose two values, using a bitmask as decision value
147 * This is equivalent to (a & mask) | (b & ~mask)
148 */
149
150static inline u32 comp(u32 a, u32 b, u32 mask)
151{
152 return ((a ^ b) & mask) ^ b;
153}