drivers/input/fixp-arith.h

   1 #ifndef _FIXP_ARITH_H
   2 #define _FIXP_ARITH_H
   3
   4 /*
   5  * Simplistic fixed-point arithmetics.
   6  * Hmm, I'm probably duplicating some code :(
   7  *
   8  * Copyright (c) 2002 Johann Deneux
   9  */
  10
  11 /*
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  25  *
  26  * Should you need to contact me, the author, you can do so by
  27  * e-mail - mail your message to <johann.deneux@gmail.com>
  28  */
  29
  30 #include <linux/types.h>
  31
  32 /* The type representing fixed-point values */
  33 typedef s16 fixp_t;
  34
  35 #define FRAC_N 8
  36 #define FRAC_MASK ((1<<FRAC_N)-1)
  37
  38 /* Not to be used directly. Use fixp_{cos,sin} */
  39 static const fixp_t cos_table[46] = {
  40         0x0100, 0x00FF, 0x00FF, 0x00FE, 0x00FD, 0x00FC, 0x00FA, 0x00F8,
  41         0x00F6, 0x00F3, 0x00F0, 0x00ED, 0x00E9, 0x00E6, 0x00E2, 0x00DD,
  42         0x00D9, 0x00D4, 0x00CF, 0x00C9, 0x00C4, 0x00BE, 0x00B8, 0x00B1,
  43         0x00AB, 0x00A4, 0x009D, 0x0096, 0x008F, 0x0087, 0x0080, 0x0078,
  44         0x0070, 0x0068, 0x005F, 0x0057, 0x004F, 0x0046, 0x003D, 0x0035,
  45         0x002C, 0x0023, 0x001A, 0x0011, 0x0008, 0x0000
  46 };
  47
  48
  49 /* a: 123 -> 123.0 */
  50 static inline fixp_t fixp_new(s16 a)
  51 {
  52         return a<<FRAC_N;
  53 }
  54
  55 /* a: 0xFFFF -> -1.0
  56       0x8000 -> 1.0
  57       0x0000 -> 0.0
  58 */
  59 static inline fixp_t fixp_new16(s16 a)
  60 {
  61         return ((s32)a)>>(16-FRAC_N);
  62 }
  63
  64 static inline fixp_t fixp_cos(unsigned int degrees)
  65 {
  66         int quadrant = (degrees / 90) & 3;
  67         unsigned int i = degrees % 90;
  68
  69         if (quadrant == 1 || quadrant == 3)
  70                 i = 90 - i;
  71
  72         i >>= 1;
  73
  74         return (quadrant == 1 || quadrant == 2)? -cos_table[i] : cos_table[i];
  75 }
  76
  77 static inline fixp_t fixp_sin(unsigned int degrees)
  78 {
  79         return -fixp_cos(degrees + 90);
  80 }
  81
  82 static inline fixp_t fixp_mult(fixp_t a, fixp_t b)
  83 {
  84         return ((s32)(a*b))>>FRAC_N;
  85 }
  86
  87 #endif