drivers/video/fbdev/c2p_core.h

   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
  22 static 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
  32 static __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
  60 static __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
 102 static __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
 129 static __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
 150 static inline u32 comp(u32 a, u32 b, u32 mask)
 151 {
 152         return ((a ^ b) & mask) ^ b;
 153 }