drivers/usb/input/fixp-arith.h

   1 #ifndef _FIXP_ARITH_H
   2 #define _FIXP_ARITH_H
   3
   4 /*
   5  * $$
   6  *
   7  * Simplistic fixed-point arithmetics.
   8  * Hmm, I'm probably duplicating some code :(
   9  *
  10  * Copyright (c) 2002 Johann Deneux
  11  */
  12
  13 /*
  14  * This program is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * This program is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program; if not, write to the Free Software
  26  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  27  *
  28  * Should you need to contact me, the author, you can do so by
  29  * e-mail - mail your message to <deneux@ifrance.com>
  30  */
  31
  32 #include <linux/types.h>
  33
  34 // The type representing fixed-point values
  35 typedef s16 fixp_t;
  36
  37 #define FRAC_N 8
  38 #define FRAC_MASK ((1<<FRAC_N)-1)
  39
  40 // Not to be used directly. Use fixp_{cos,sin}
  41 static fixp_t cos_table[45] = {
  42         0x0100, 0x00FF, 0x00FF, 0x00FE, 0x00FD, 0x00FC, 0x00FA, 0x00F8,
  43         0x00F6, 0x00F3, 0x00F0, 0x00ED, 0x00E9, 0x00E6, 0x00E2, 0x00DD,
  44         0x00D9, 0x00D4, 0x00CF, 0x00C9, 0x00C4, 0x00BE, 0x00B8, 0x00B1,
  45         0x00AB, 0x00A4, 0x009D, 0x0096, 0x008F, 0x0087, 0x0080, 0x0078,
  46         0x0070, 0x0068, 0x005F, 0x0057, 0x004F, 0x0046, 0x003D, 0x0035,
  47         0x002C, 0x0023, 0x001A, 0x0011, 0x0008
  48 };
  49
  50
  51 /* a: 123 -> 123.0 */
  52 static inline fixp_t fixp_new(s16 a)
  53 {
  54         return a<<FRAC_N;
  55 }
  56
  57 /* a: 0xFFFF -> -1.0
  58       0x8000 -> 1.0
  59       0x0000 -> 0.0
  60 */
  61 static inline fixp_t fixp_new16(s16 a)
  62 {
  63         return ((s32)a)>>(16-FRAC_N);
  64 }
  65
  66 static inline fixp_t fixp_cos(unsigned int degrees)
  67 {
  68         int quadrant = (degrees / 90) & 3;
  69         unsigned int i = degrees % 90;
  70
  71         if (quadrant == 1 || quadrant == 3) {
  72                 i = 89 - i;
  73         }
  74
  75         i >>= 1;
  76
  77         return (quadrant == 1 || quadrant == 2)? -cos_table[i] : cos_table[i];
  78 }
  79
  80 static inline fixp_t fixp_sin(unsigned int degrees)
  81 {
  82         return -fixp_cos(degrees + 90);
  83 }
  84
  85 static inline fixp_t fixp_mult(fixp_t a, fixp_t b)
  86 {
  87         return ((s32)(a*b))>>FRAC_N;
  88 }
  89
  90 #endif