dvb_math.c

V4l driver for DVB HD

/*
 *    dvb_math.c - Integer math functions suitable for DVB driver use
 *
 *    Copyright (C) 2006 Rusty Scott <[e-mail]>
 *
 *    Taken from or51134 and or51211 front end modules which are
 *    Copyright (C) 2005 Kirk Lapray <[e-mail]>
 *
 *    which lifted the integer logarithm code, without modification, directly
 *    from pcHDTV code which is
 *    Copyright (C) 2002 pcHDTV,Inc. & Jack Kelliher <[e-mail]>
 *
 *    All of which was published under the GNU GPL.
 *
 *    Permission has been granted by the original copyright holder to
 *    distribute this code in the dvb_core library under the GNU Lesser
 *    General Public license which is hereafter referenced:
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU Lesser General Public License as
 *    published by the Free Software Foundation; either version 2.1 of the
 *    License, or (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Lesser General Public License for more details.
 *
 *    You should have received a copy of the GNU Lesser General Public
 *    License along with this program; if not, write to the Free Software
 *    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
 *    USA
 *
 */

/*
 *    Notes:
 *    There are several frontends in the DVB set that attempt to give a
 *    real value for the SNR in dB.  This module pulls that code into a single
 *    place for maintenance and fixes the algorithmic problems of the code
 *    found in the OR51132 and 51211 frontends.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <asm/byteorder.h>

#include "dvb_math.h"

/* log10-1 table at .5 increments from 1 to 100.5 */
static unsigned int i100x20log10[] = {0, 0,
     0,  352,  602,  795,  954, 1088, 1204, 1306, 1397, 1480,
  1556, 1625, 1690, 1750, 1806, 1858, 1908, 1955, 2000, 2042,
  2082, 2121, 2158, 2193, 2227, 2260, 2292, 2322, 2352, 2380,
  2408, 2434, 2460, 2486, 2510, 2534, 2557, 2580, 2602, 2623,
  2644, 2664, 2684, 2704, 2723, 2742, 2760, 2778, 2795, 2813,
  2829, 2846, 2862, 2878, 2894, 2909, 2924, 2939, 2954, 2968,
  2982, 2996, 3010, 3023, 3037, 3050, 3062, 3075, 3088, 3100,
  3112, 3124, 3136, 3148, 3159, 3170, 3182, 3193, 3204, 3214,
  3225, 3236, 3246, 3256, 3266, 3276, 3286, 3296, 3306, 3316,
  3325, 3334, 3344, 3353, 3362, 3371, 3380, 3389, 3397, 3406,
  3415, 3423, 3432, 3440, 3448, 3456, 3464, 3472, 3480, 3488,
  3496, 3504, 3511, 3519, 3526, 3534, 3541, 3549, 3556, 3563,
  3570, 3577, 3584, 3591, 3598, 3605, 3612, 3619, 3625, 3632,
  3639, 3645, 3652, 3658, 3665, 3671, 3677, 3683, 3690, 3696,
  3702, 3708, 3714, 3720, 3726, 3732, 3738, 3744, 3750, 3755,
  3761, 3767, 3772, 3778, 3784, 3789, 3795, 3800, 3806, 3811,
  3816, 3822, 3827, 3832, 3838, 3843, 3848, 3853, 3858, 3863,
  3868, 3874, 3879, 3884, 3888, 3893, 3898, 3903, 3908, 3913,
  3918, 3922, 3927, 3932, 3936, 3941, 3946, 3950, 3955, 3960,
  3964, 3969, 3973, 3978, 3982, 3986, 3991, 3995, 4000, 4004,
};

static unsigned int denom[] = {1,10,100,1000,10000,100000,1000000,10000000,100000000};

unsigned int i10Log10(u32 val)
{
	unsigned int rntval = 0;
	u32 tmp = val;
	unsigned int exp = 0;

	while(tmp > 100) {tmp /= 10; exp++;}

	val = (2 * val)/denom[exp];
	rntval = 1000*exp;

	rntval += i100x20log10[val]/2;
	return rntval;
}
EXPORT_SYMBOL(i10Log10);

unsigned int i20Log10(u32 val)
{
	return 2*i10Log10(val);
}
EXPORT_SYMBOL(i20Log10);

/*
 * Local variables:
 * c-basic-offset: 8
 * End:
 */