V4L/DVB (3988): Add math routines required by DVB demods

dvb-core-objs = dvbdev.o dmxdev.o dvb_demux.o dvb_filter.o 	\

		dvb_ca_en50221.o dvb_frontend.o 		\

		dvb_net.o dvb_ringbuffer.o

		dvb_net.o dvb_ringbuffer.o dvb_math.o

obj-$(CONFIG_DVB_CORE) += dvb-core.o

/*

 * dvb-math provides some complex fixed-point math

 * operations shared between the dvb related stuff

 *

 * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)

 *

 * This library 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 library; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

 */

#include <linux/bitops.h>

#include <linux/kernel.h>

#include <asm/bug.h>

#include "dvb_math.h"

const unsigned short logtable[256] = {

	0x0000, 0x0171, 0x02e0, 0x044e, 0x05ba, 0x0725, 0x088e, 0x09f7,

	0x0b5d, 0x0cc3, 0x0e27, 0x0f8a, 0x10eb, 0x124b, 0x13aa, 0x1508,

	0x1664, 0x17bf, 0x1919, 0x1a71, 0x1bc8, 0x1d1e, 0x1e73, 0x1fc6,

	0x2119, 0x226a, 0x23ba, 0x2508, 0x2656, 0x27a2, 0x28ed, 0x2a37,

	0x2b80, 0x2cc8, 0x2e0f, 0x2f54, 0x3098, 0x31dc, 0x331e, 0x345f,

	0x359f, 0x36de, 0x381b, 0x3958, 0x3a94, 0x3bce, 0x3d08, 0x3e41,

	0x3f78, 0x40af, 0x41e4, 0x4319, 0x444c, 0x457f, 0x46b0, 0x47e1,

	0x4910, 0x4a3f, 0x4b6c, 0x4c99, 0x4dc5, 0x4eef, 0x5019, 0x5142,

	0x526a, 0x5391, 0x54b7, 0x55dc, 0x5700, 0x5824, 0x5946, 0x5a68,

	0x5b89, 0x5ca8, 0x5dc7, 0x5ee5, 0x6003, 0x611f, 0x623a, 0x6355,

	0x646f, 0x6588, 0x66a0, 0x67b7, 0x68ce, 0x69e4, 0x6af8, 0x6c0c,

	0x6d20, 0x6e32, 0x6f44, 0x7055, 0x7165, 0x7274, 0x7383, 0x7490,

	0x759d, 0x76aa, 0x77b5, 0x78c0, 0x79ca, 0x7ad3, 0x7bdb, 0x7ce3,

	0x7dea, 0x7ef0, 0x7ff6, 0x80fb, 0x81ff, 0x8302, 0x8405, 0x8507,

	0x8608, 0x8709, 0x8809, 0x8908, 0x8a06, 0x8b04, 0x8c01, 0x8cfe,

	0x8dfa, 0x8ef5, 0x8fef, 0x90e9, 0x91e2, 0x92db, 0x93d2, 0x94ca,

	0x95c0, 0x96b6, 0x97ab, 0x98a0, 0x9994, 0x9a87, 0x9b7a, 0x9c6c,

	0x9d5e, 0x9e4f, 0x9f3f, 0xa02e, 0xa11e, 0xa20c, 0xa2fa, 0xa3e7,

	0xa4d4, 0xa5c0, 0xa6ab, 0xa796, 0xa881, 0xa96a, 0xaa53, 0xab3c,

	0xac24, 0xad0c, 0xadf2, 0xaed9, 0xafbe, 0xb0a4, 0xb188, 0xb26c,

	0xb350, 0xb433, 0xb515, 0xb5f7, 0xb6d9, 0xb7ba, 0xb89a, 0xb97a,

	0xba59, 0xbb38, 0xbc16, 0xbcf4, 0xbdd1, 0xbead, 0xbf8a, 0xc065,

	0xc140, 0xc21b, 0xc2f5, 0xc3cf, 0xc4a8, 0xc580, 0xc658, 0xc730,

	0xc807, 0xc8de, 0xc9b4, 0xca8a, 0xcb5f, 0xcc34, 0xcd08, 0xcddc,

	0xceaf, 0xcf82, 0xd054, 0xd126, 0xd1f7, 0xd2c8, 0xd399, 0xd469,

	0xd538, 0xd607, 0xd6d6, 0xd7a4, 0xd872, 0xd93f, 0xda0c, 0xdad9,

	0xdba5, 0xdc70, 0xdd3b, 0xde06, 0xded0, 0xdf9a, 0xe063, 0xe12c,

	0xe1f5, 0xe2bd, 0xe385, 0xe44c, 0xe513, 0xe5d9, 0xe69f, 0xe765,

	0xe82a, 0xe8ef, 0xe9b3, 0xea77, 0xeb3b, 0xebfe, 0xecc1, 0xed83,

	0xee45, 0xef06, 0xefc8, 0xf088, 0xf149, 0xf209, 0xf2c8, 0xf387,

	0xf446, 0xf505, 0xf5c3, 0xf680, 0xf73e, 0xf7fb, 0xf8b7, 0xf973,

	0xfa2f, 0xfaea, 0xfba5, 0xfc60, 0xfd1a, 0xfdd4, 0xfe8e, 0xff47

};

unsigned int intlog2(u32 value)

{

	/**

	 *	returns: log2(value) * 2^24

	 *	wrong result if value = 0 (log2(0) is undefined)

	 */

	unsigned int msb;

	unsigned int logentry;

	unsigned int significand;

	unsigned int interpolation;

	if (unlikely(value == 0)) {

		WARN_ON(1);

		return 0;

	}

	/* first detect the msb (count begins at 0) */

	msb = fls(value) - 1;

	/**

	 *	now we use a logtable after the following method:

	 *

	 *	log2(2^x * y) * 2^24 = x * 2^24 + log2(y) * 2^24

	 *	where x = msb and therefore 1 <= y < 2

	 *	first y is determined by shifting the value left

	 *	so that msb is bit 31

	 *		0x00231f56 -> 0x8C7D5800

	 *	the result is y * 2^31 -> "significand"

	 *	then the highest 9 bits are used for a table lookup

	 *	the highest bit is discarded because it's always set

	 *	the highest nine bits in our example are 100011000

	 *	so we would use the entry 0x18

	 */

	significand = value << (31 - msb);

	logentry = (significand >> 23) & 0xff;

	/**

	 *	last step we do is interpolation because of the

	 *	limitations of the log table the error is that part of

	 *	the significand which isn't used for lookup then we

	 *	compute the ratio between the error and the next table entry

	 *	and interpolate it between the log table entry used and the

	 *	next one the biggest error possible is 0x7fffff

	 *	(in our example it's 0x7D5800)

	 *	needed value for next table entry is 0x800000

	 *	so the interpolation is

	 *	(error / 0x800000) * (logtable_next - logtable_current)

	 *	in the implementation the division is moved to the end for

	 *	better accuracy there is also an overflow correction if

	 *	logtable_next is 256

	 */

	interpolation = ((significand & 0x7fffff) *

			((logtable[(logentry + 1) & 0xff] -

			  logtable[logentry]) & 0xffff)) >> 15;

	/* now we return the result */

	return ((msb << 24) + (logtable[logentry] << 8) + interpolation);

}

EXPORT_SYMBOL(intlog2);

unsigned int intlog10(u32 value)

{

	/**

	 *	returns: log10(value) * 2^24

	 *	wrong result if value = 0 (log10(0) is undefined)

	 */

	u64 log;

	if (unlikely(value == 0)) {

		WARN_ON(1);

		return 0;

	}

	log = intlog2(value);

	/**

	 *	we use the following method:

	 *	log10(x) = log2(x) * log10(2)

	 */

	return (log * 646456993) >> 31;

}

EXPORT_SYMBOL(intlog10);

/*

 * dvb-math provides some complex fixed-point math

 * operations shared between the dvb related stuff

 *

 * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)

 *

 * This library 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 library; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

 */

#ifndef __DVB_MATH_H

#define __DVB_MATH_H

#include <linux/types.h>

/**

 * computes log2 of a value; the result is shifted left by 24 bits

 *

 * to use rational values you can use the following method:

 *   intlog2(value) = intlog2(value * 2^x) - x * 2^24

 *

 * example: intlog2(8) will give 3 << 24 = 3 * 2^24

 * example: intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24

 * example: intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24

 *

 * @param value The value (must be != 0)

 * @return log2(value) * 2^24

 */

extern unsigned int intlog2(u32 value);

/**

 * computes log10 of a value; the result is shifted left by 24 bits

 *

 * to use rational values you can use the following method:

 *   intlog10(value) = intlog10(value * 10^x) - x * 2^24

 *

 * example: intlog10(1000) will give 3 << 24 = 3 * 2^24

 *   due to the implementation intlog10(1000) might be not exactly 3 * 2^24

 *

 * look at intlog2 for similar examples

 *

 * @param value The value (must be != 0)

 * @return log10(value) * 2^24

 */

extern unsigned int intlog10(u32 value);

#endif