diff -urN dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/bit_operations.h patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/bit_operations.h
--- dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/bit_operations.h	1969-12-31 19:00:00.000000000 -0500
+++ patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/bit_operations.h	2012-05-25 13:39:10.000000000 -0400
@@ -0,0 +1,228 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * bit_operations.h - Various bit level operations, such as bit reversal
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2006 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: bit_operations.h,v 1.11 2006/11/28 15:37:03 steveu Exp $
+ */
+
+/*! \file */
+
+#if !defined(_BIT_OPERATIONS_H_)
+#define _BIT_OPERATIONS_H_
+
+#if defined(__i386__)  ||  defined(__x86_64__)
+/*! \brief Find the bit position of the highest set bit in a word
+    \param bits The word to be searched
+    \return The bit number of the highest set bit, or -1 if the word is zero. */
+static __inline__ int top_bit(unsigned int bits)
+{
+	int res;
+
+	__asm__(" xorl %[res],%[res];\n"
+		" decl %[res];\n"
+		" bsrl %[bits],%[res]\n"
+		:[res] "=&r" (res)
+		:[bits] "rm"(bits)
+	);
+	return res;
+}
+
+/*! \brief Find the bit position of the lowest set bit in a word
+    \param bits The word to be searched
+    \return The bit number of the lowest set bit, or -1 if the word is zero. */
+static __inline__ int bottom_bit(unsigned int bits)
+{
+	int res;
+
+	__asm__(" xorl %[res],%[res];\n"
+		" decl %[res];\n"
+		" bsfl %[bits],%[res]\n"
+		:[res] "=&r" (res)
+		:[bits] "rm"(bits)
+	);
+	return res;
+}
+#else
+static __inline__ int top_bit(unsigned int bits)
+{
+	int i;
+
+	if (bits == 0)
+		return -1;
+	i = 0;
+	if (bits & 0xFFFF0000) {
+		bits &= 0xFFFF0000;
+		i += 16;
+	}
+	if (bits & 0xFF00FF00) {
+		bits &= 0xFF00FF00;
+		i += 8;
+	}
+	if (bits & 0xF0F0F0F0) {
+		bits &= 0xF0F0F0F0;
+		i += 4;
+	}
+	if (bits & 0xCCCCCCCC) {
+		bits &= 0xCCCCCCCC;
+		i += 2;
+	}
+	if (bits & 0xAAAAAAAA) {
+		bits &= 0xAAAAAAAA;
+		i += 1;
+	}
+	return i;
+}
+
+static __inline__ int bottom_bit(unsigned int bits)
+{
+	int i;
+
+	if (bits == 0)
+		return -1;
+	i = 32;
+	if (bits & 0x0000FFFF) {
+		bits &= 0x0000FFFF;
+		i -= 16;
+	}
+	if (bits & 0x00FF00FF) {
+		bits &= 0x00FF00FF;
+		i -= 8;
+	}
+	if (bits & 0x0F0F0F0F) {
+		bits &= 0x0F0F0F0F;
+		i -= 4;
+	}
+	if (bits & 0x33333333) {
+		bits &= 0x33333333;
+		i -= 2;
+	}
+	if (bits & 0x55555555) {
+		bits &= 0x55555555;
+		i -= 1;
+	}
+	return i;
+}
+#endif
+
+/*! \brief Bit reverse a byte.
+    \param data The byte to be reversed.
+    \return The bit reversed version of data. */
+static __inline__ uint8_t bit_reverse8(uint8_t x)
+{
+#if defined(__i386__)  ||  defined(__x86_64__)
+	/* If multiply is fast */
+	return ((x * 0x0802U & 0x22110U) | (x * 0x8020U & 0x88440U)) *
+	    0x10101U >> 16;
+#else
+	/* If multiply is slow, but we have a barrel shifter */
+	x = (x >> 4) | (x << 4);
+	x = ((x & 0xCC) >> 2) | ((x & 0x33) << 2);
+	return ((x & 0xAA) >> 1) | ((x & 0x55) << 1);
+#endif
+}
+
+/*! \brief Bit reverse a 16 bit word.
+    \param data The word to be reversed.
+    \return The bit reversed version of data. */
+uint16_t bit_reverse16(uint16_t data);
+
+/*! \brief Bit reverse a 32 bit word.
+    \param data The word to be reversed.
+    \return The bit reversed version of data. */
+uint32_t bit_reverse32(uint32_t data);
+
+/*! \brief Bit reverse each of the four bytes in a 32 bit word.
+    \param data The word to be reversed.
+    \return The bit reversed version of data. */
+uint32_t bit_reverse_4bytes(uint32_t data);
+
+/*! \brief Find the number of set bits in a 32 bit word.
+    \param x The word to be searched.
+    \return The number of set bits. */
+int one_bits32(uint32_t x);
+
+/*! \brief Create a mask as wide as the number in a 32 bit word.
+    \param x The word to be searched.
+    \return The mask. */
+uint32_t make_mask32(uint32_t x);
+
+/*! \brief Create a mask as wide as the number in a 16 bit word.
+    \param x The word to be searched.
+    \return The mask. */
+uint16_t make_mask16(uint16_t x);
+
+/*! \brief Find the least significant one in a word, and return a word
+           with just that bit set.
+    \param x The word to be searched.
+    \return The word with the single set bit. */
+static __inline__ uint32_t least_significant_one32(uint32_t x)
+{
+	return (x & (-(int32_t) x));
+}
+
+/*! \brief Find the most significant one in a word, and return a word
+           with just that bit set.
+    \param x The word to be searched.
+    \return The word with the single set bit. */
+static __inline__ uint32_t most_significant_one32(uint32_t x)
+{
+#if defined(__i386__)  ||  defined(__x86_64__)
+	return 1 << top_bit(x);
+#else
+	x = make_mask32(x);
+	return (x ^ (x >> 1));
+#endif
+}
+
+/*! \brief Find the parity of a byte.
+    \param x The byte to be checked.
+    \return 1 for odd, or 0 for even. */
+static __inline__ int parity8(uint8_t x)
+{
+	x = (x ^ (x >> 4)) & 0x0F;
+	return (0x6996 >> x) & 1;
+}
+
+/*! \brief Find the parity of a 16 bit word.
+    \param x The word to be checked.
+    \return 1 for odd, or 0 for even. */
+static __inline__ int parity16(uint16_t x)
+{
+	x ^= (x >> 8);
+	x = (x ^ (x >> 4)) & 0x0F;
+	return (0x6996 >> x) & 1;
+}
+
+/*! \brief Find the parity of a 32 bit word.
+    \param x The word to be checked.
+    \return 1 for odd, or 0 for even. */
+static __inline__ int parity32(uint32_t x)
+{
+	x ^= (x >> 16);
+	x ^= (x >> 8);
+	x = (x ^ (x >> 4)) & 0x0F;
+	return (0x6996 >> x) & 1;
+}
+
+#endif
+/*- End of file ------------------------------------------------------------*/
diff -urN dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/dahdi_echocan_oslec.c patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/dahdi_echocan_oslec.c
--- dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/dahdi_echocan_oslec.c	2011-11-15 01:44:09.000000000 -0500
+++ patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/dahdi_echocan_oslec.c	2012-05-25 13:39:12.000000000 -0400
@@ -1,25 +1,111 @@
 /*
- * DAHDI Telephony Interface to the Open Source Line Echo Canceller (OSLEC)
+ * ECHO_CAN_OSLEC
+ *
+ * Written by Eric Wilde <ewilde@bsmdevelopment.com>
+ *
+ * Adapted from OSLEC shim written by Tzafrir Cohen
+ *         <tzafrir.cohen@xorcom.com>
  *
- * Written by Tzafrir Cohen <tzafrir.cohen@xorcom.com>
  * Copyright (C) 2008 Xorcom, Inc.
  *
  * All rights reserved.
  *
  * Based on dahdi_echocan_hpec.c, Copyright (C) 2006-2008 Digium, Inc.
  *
+ * Echo canceller written by Steve Underwood <steveu@coppice.org>
+ *         and David Rowe <david_at_rowetel_dot_com>
+ *
+ * Copyright (C) 2001, 2003 Steve Underwood, 2007 David Rowe
+ *
+ * Based on a bit from here, a bit from there, eye of toad, ear of
+ * bat, 15 years of failed attempts by David and a few fried brain
+ * cells.
+ *
+ * All rights reserved.
+ *
  * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
+ * it under the terms of the GNU General Public License version 2, as
  * published by the Free Software Foundation.
- * 
+ *
  * 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 General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* Implementation Notes
+ * David Rowe
+ * April 2007
+ *
+ * This code started life as Steve's NLMS algorithm with a tap
+ * rotation algorithm to handle divergence during double talk.  I
+ * added a Geigel Double Talk Detector (DTD) [2] and performed some
+ * G168 tests.  However I had trouble meeting the G168 requirements,
+ * especially for double talk - there were always cases where my DTD
+ * failed, for example where near end speech was under the 6dB
+ * threshold required for declaring double talk.
+ *
+ * So I tried a two path algorithm [1], which has so far given better
+ * results.  The original tap rotation/Geigel algorithm is available
+ * in SVN http://svn.rowetel.com/software/oslec/tags/before_16bit.
+ * It's probably possible to make it work if some one wants to put some
+ * serious work into it.
+ *
+ * At present no special treatment is provided for tones, which
+ * generally cause NLMS algorithms to diverge.  Initial runs of a
+ * subset of the G168 tests for tones (e.g ./echo_test 6) show the
+ * current algorithm is passing OK, which is kind of surprising.  The
+ * full set of tests needs to be performed to confirm this result.
+ *
+ * One other interesting change is that I have managed to get the NLMS
+ * code to work with 16 bit coefficients, rather than the original 32
+ * bit coefficents.  This reduces the MIPs and storage required.
+ * I evaulated the 16 bit port using g168_tests.sh and listening tests
+ * on 4 real-world samples.
+ *
+ * I also attempted the implementation of a block based NLMS update
+ * [2] but although this passes g168_tests.sh it didn't converge well
+ * on the real-world samples.  I have no idea why, perhaps a scaling
+ * problem.  The block based code is also available in SVN
+ * http://svn.rowetel.com/software/oslec/tags/before_16bit.  If this
+ * code can be debugged, it will lead to further reduction in MIPS, as
+ * the block update code maps nicely onto DSP instruction sets (it's a
+ * dot product) compared to the current sample-by-sample update.
+ *
+ * Steve also has some nice notes on echo cancellers in echo.h
+ *
+ * References:
+ *
+ * [1] Ochiai, Areseki, and Ogihara, "Echo Canceller with Two Echo
+ *     Path Models", IEEE Transactions on communications, COM-25,
+ *     No. 6, June
+ *     1977.
+ *     http://www.rowetel.com/images/echo/dual_path_paper.pdf
+ *
+ * [2] The classic, very useful paper that tells you how to
+ *     actually build a real world echo canceller:
+ *       Messerschmitt, Hedberg, Cole, Haoui, Winship, "Digital Voice
+ *       Echo Canceller with a TMS320020,
+ *       http://www.rowetel.com/images/echo/spra129.pdf
+ *
+ * [3] I have written a series of blog posts on this work, here is
+ *     Part 1: http://www.rowetel.com/blog/?p=18
+ *
+ * [4] The source code http://svn.rowetel.com/software/oslec/
+ *
+ * [5] A nice reference on LMS filters:
+ *       http://en.wikipedia.org/wiki/Least_mean_squares_filter
+ *
+ * Credits:
+ *
+ * Thanks to Steve Underwood, Jean-Marc Valin, and Ramakrishnan
+ * Muthukrishnan for their suggestions and email discussions.  Thanks
+ * also to those people who collected echo samples for me such as
+ * Mark, Pawel, and Pavel.
  */
 
 #include <linux/kernel.h>
@@ -30,28 +116,33 @@
 #include <linux/ctype.h>
 #include <linux/moduleparam.h>
 
-/* Fix this if OSLEC is elsewhere */
-#include "../staging/echo/oslec.h"
-//#include <linux/oslec.h>
+/* Stuff specific to this echo canceller */
+#include "bit_operations.h"
+#include "echo.h"
+#include "oslec.h"
 
+/* DAHDI stuff */
 #include <dahdi/kernel.h>
 
+#define MIN_TX_POWER_FOR_ADAPTION   64
+#define MIN_RX_POWER_FOR_ADAPTION   64
+#define DTD_HANGOVER               600	/* 600 samples, or 75ms     */
+#define DC_LOG2BETA                  3	/* log2() of DC filter Beta */
+
 #define module_printk(level, fmt, args...) printk(level "%s: " fmt, THIS_MODULE->name, ## args)
 
+/* The functions we expose the echo canceller factory */
+static const char *name = "OSLEC";
+static const char *ec_name(const struct dahdi_chan *chan) { return name; }
 static int echo_can_create(struct dahdi_chan *chan, struct dahdi_echocanparams *ecp,
 			   struct dahdi_echocanparam *p, struct dahdi_echocan_state **ec);
 static void echo_can_free(struct dahdi_chan *chan, struct dahdi_echocan_state *ec);
 static void echo_can_process(struct dahdi_echocan_state *ec, short *isig, const short *iref, u32 size);
 static int echo_can_traintap(struct dahdi_echocan_state *ec, int pos, short val);
-#ifdef CONFIG_DAHDI_ECHOCAN_PROCESS_TX
-static void echo_can_hpf_tx(struct dahdi_echocan_state *ec,
-			    short *tx, u32 size);
-#endif
-static const char *name = "OSLEC";
-static const char *ec_name(const struct dahdi_chan *chan) { return name; }
 
+/* Constants used to anchor the echo canceller */
 static const struct dahdi_echocan_factory my_factory = {
-	.get_name = ec_name,
+ 	.get_name = ec_name,
 	.owner = THIS_MODULE,
 	.echocan_create = echo_can_create,
 };
@@ -60,9 +151,6 @@
 	.echocan_free = echo_can_free,
 	.echocan_process = echo_can_process,
 	.echocan_traintap = echo_can_traintap,
-#ifdef CONFIG_DAHDI_ECHOCAN_PROCESS_TX
-	.echocan_process_tx = echo_can_hpf_tx,
-#endif
 };
 
 struct ec_pvt {
@@ -126,20 +214,503 @@
 	return 1;
 }
 
-#ifdef CONFIG_DAHDI_ECHOCAN_PROCESS_TX
-static void echo_can_hpf_tx(struct dahdi_echocan_state *ec, short *tx, u32 size)
+/* adapting coeffs using the traditional stochastic descent (N)LMS algorithm */
+
+#ifdef __bfin__
+static void __inline__ lms_adapt_bg(struct oslec_state *ec, int clean,
+				    int shift)
 {
-	struct ec_pvt *pvt = dahdi_to_pvt(ec);
-	u32 SampleNum;
+	int i, j;
+	int offset1;
+	int offset2;
+	int factor;
+	int exp;
+	int16_t *phist;
+	int n;
+
+	if (shift > 0)
+		factor = clean << shift;
+	else
+		factor = clean >> -shift;
+
+	/* Update the FIR taps */
+
+	offset2 = ec->curr_pos;
+	offset1 = ec->taps - offset2;
+	phist = &ec->fir_state_bg.history[offset2];
+
+	/* st: and en: help us locate the assembler in echo.s */
+
+	//asm("st:");
+	n = ec->taps;
+	for (i = 0, j = offset2; i < n; i++, j++) {
+		exp = *phist++ * factor;
+		ec->fir_taps16[1][i] += (int16_t) ((exp + (1 << 14)) >> 15);
+	}
+	//asm("en:");
 
-	for (SampleNum = 0; SampleNum < size; SampleNum++, tx++) {
-		short iCleanSample;
+	/* Note the asm for the inner loop above generated by Blackfin gcc
+	   4.1.1 is pretty good (note even parallel instructions used):
+
+	   R0 = W [P0++] (X);
+	   R0 *= R2;
+	   R0 = R0 + R3 (NS) ||
+	   R1 = W [P1] (X) ||
+	   nop;
+	   R0 >>>= 15;
+	   R0 = R0 + R1;
+	   W [P1++] = R0;
+
+	   A block based update algorithm would be much faster but the
+	   above can't be improved on much.  Every instruction saved in
+	   the loop above is 2 MIPs/ch!  The for loop above is where the
+	   Blackfin spends most of it's time - about 17 MIPs/ch measured
+	   with speedtest.c with 256 taps (32ms).  Write-back and
+	   Write-through cache gave about the same performance.
+	 */
+}
+
+/*
+   IDEAS for further optimisation of lms_adapt_bg():
+
+   1/ The rounding is quite costly.  Could we keep as 32 bit coeffs
+   then make filter pluck the MS 16-bits of the coeffs when filtering?
+   However this would lower potential optimisation of filter, as I
+   think the dual-MAC architecture requires packed 16 bit coeffs.
+
+   2/ Block based update would be more efficient, as per comments above,
+   could use dual MAC architecture.
+
+   3/ Look for same sample Blackfin LMS code, see if we can get dual-MAC
+   packing.
+
+   4/ Execute the whole e/c in a block of say 20ms rather than sample
+   by sample.  Processing a few samples every ms is inefficient.
+*/
+
+#else
+static __inline__ void lms_adapt_bg(struct oslec_state *ec, int clean,
+				    int shift)
+{
+	int i;
+
+	int offset1;
+	int offset2;
+	int factor;
+	int exp;
+
+	if (shift > 0)
+		factor = clean << shift;
+	else
+		factor = clean >> -shift;
+
+	/* Update the FIR taps */
+
+	offset2 = ec->curr_pos;
+	offset1 = ec->taps - offset2;
+
+	for (i = ec->taps - 1; i >= offset1; i--) {
+		exp = (ec->fir_state_bg.history[i - offset1] * factor);
+		ec->fir_taps16[1][i] += (int16_t) ((exp + (1 << 14)) >> 15);
+	}
+	for (; i >= 0; i--) {
+		exp = (ec->fir_state_bg.history[i + offset2] * factor);
+		ec->fir_taps16[1][i] += (int16_t) ((exp + (1 << 14)) >> 15);
+	}
+}
+#endif
+
+struct oslec_state *oslec_create(int len, int adaption_mode)
+{
+	struct oslec_state *ec;
+	int i;
+
+	ec = kzalloc(sizeof(*ec), GFP_KERNEL);
+	if (!ec)
+		return NULL;
+
+	ec->taps = len;
+	ec->log2taps = top_bit(len);
+	ec->curr_pos = ec->taps - 1;
+
+	for (i = 0; i < 2; i++) {
+		ec->fir_taps16[i] =
+		    kcalloc(ec->taps, sizeof(int16_t), GFP_KERNEL);
+		if (!ec->fir_taps16[i])
+			goto error_oom;
+	}
+
+	fir16_create(&ec->fir_state, ec->fir_taps16[0], ec->taps);
+	fir16_create(&ec->fir_state_bg, ec->fir_taps16[1], ec->taps);
+
+	for (i = 0; i < 5; i++) {
+		ec->xvtx[i] = ec->yvtx[i] = ec->xvrx[i] = ec->yvrx[i] = 0;
+	}
+
+	ec->cng_level = 1000;
+	oslec_adaption_mode(ec, adaption_mode);
+
+	ec->snapshot = kcalloc(ec->taps, sizeof(int16_t), GFP_KERNEL);
+	if (!ec->snapshot)
+		goto error_oom;
+
+	ec->cond_met = 0;
+	ec->Pstates = 0;
+	ec->Ltxacc = ec->Lrxacc = ec->Lcleanacc = ec->Lclean_bgacc = 0;
+	ec->Ltx = ec->Lrx = ec->Lclean = ec->Lclean_bg = 0;
+	ec->tx_1 = ec->tx_2 = ec->rx_1 = ec->rx_2 = 0;
+	ec->Lbgn = ec->Lbgn_acc = 0;
+	ec->Lbgn_upper = 200;
+	ec->Lbgn_upper_acc = ec->Lbgn_upper << 13;
+
+	return ec;
+
+      error_oom:
+	for (i = 0; i < 2; i++)
+		kfree(ec->fir_taps16[i]);
+
+	kfree(ec);
+	return NULL;
+}
 
-		iCleanSample = oslec_hpf_tx(pvt->oslec, *tx);
-		*tx = iCleanSample;
+void oslec_free(struct oslec_state *ec)
+{
+	int i;
+
+	fir16_free(&ec->fir_state);
+	fir16_free(&ec->fir_state_bg);
+	for (i = 0; i < 2; i++)
+		kfree(ec->fir_taps16[i]);
+	kfree(ec->snapshot);
+	kfree(ec);
+}
+
+void oslec_adaption_mode(struct oslec_state *ec, int adaption_mode)
+{
+	ec->adaption_mode = adaption_mode;
+}
+
+void oslec_flush(struct oslec_state *ec)
+{
+	int i;
+
+	ec->Ltxacc = ec->Lrxacc = ec->Lcleanacc = ec->Lclean_bgacc = 0;
+	ec->Ltx = ec->Lrx = ec->Lclean = ec->Lclean_bg = 0;
+	ec->tx_1 = ec->tx_2 = ec->rx_1 = ec->rx_2 = 0;
+
+	ec->Lbgn = ec->Lbgn_acc = 0;
+	ec->Lbgn_upper = 200;
+	ec->Lbgn_upper_acc = ec->Lbgn_upper << 13;
+
+	ec->nonupdate_dwell = 0;
+
+	fir16_flush(&ec->fir_state);
+	fir16_flush(&ec->fir_state_bg);
+	ec->fir_state.curr_pos = ec->taps - 1;
+	ec->fir_state_bg.curr_pos = ec->taps - 1;
+	for (i = 0; i < 2; i++)
+		memset(ec->fir_taps16[i], 0, ec->taps * sizeof(int16_t));
+
+	ec->curr_pos = ec->taps - 1;
+	ec->Pstates = 0;
+}
+
+void oslec_snapshot(struct oslec_state *ec)
+{
+	memcpy(ec->snapshot, ec->fir_taps16[0], ec->taps * sizeof(int16_t));
+}
+
+/* Dual Path Echo Canceller ------------------------------------------------*/
+
+int16_t oslec_update(struct oslec_state *ec, int16_t tx, int16_t rx)
+{
+	int32_t echo_value;
+	int clean_bg;
+	int tmp, tmp1;
+
+	/* Input scaling was found be required to prevent problems when tx
+	   starts clipping.  Another possible way to handle this would be the
+	   filter coefficent scaling. */
+
+	ec->tx = tx;
+	ec->rx = rx;
+	tx >>= 1;
+	rx >>= 1;
+
+	/*
+	   Filter DC, 3dB point is 160Hz (I think), note 32 bit precision required
+	   otherwise values do not track down to 0. Zero at DC, Pole at (1-Beta)
+	   only real axis.  Some chip sets (like Si labs) don't need
+	   this, but something like a $10 X100P card does.  Any DC really slows
+	   down convergence.
+
+	   Note: removes some low frequency from the signal, this reduces
+	   the speech quality when listening to samples through headphones
+	   but may not be obvious through a telephone handset.
+
+	   Note that the 3dB frequency in radians is approx Beta, e.g. for
+	   Beta = 2^(-3) = 0.125, 3dB freq is 0.125 rads = 159Hz.
+	 */
+
+	if (ec->adaption_mode & ECHO_CAN_USE_RX_HPF) {
+		tmp = rx << 15;
+#if 1
+		/* Make sure the gain of the HPF is 1.0. This can still saturate a little under
+		   impulse conditions, and it might roll to 32768 and need clipping on sustained peak
+		   level signals. However, the scale of such clipping is small, and the error due to
+		   any saturation should not markedly affect the downstream processing. */
+		tmp -= (tmp >> 4);
+#endif
+		ec->rx_1 += -(ec->rx_1 >> DC_LOG2BETA) + tmp - ec->rx_2;
+
+		/* hard limit filter to prevent clipping.  Note that at this stage
+		   rx should be limited to +/- 16383 due to right shift above */
+		tmp1 = ec->rx_1 >> 15;
+		if (tmp1 > 16383)
+			tmp1 = 16383;
+		if (tmp1 < -16383)
+			tmp1 = -16383;
+		rx = tmp1;
+		ec->rx_2 = tmp;
+	}
+
+	/* Block average of power in the filter states.  Used for
+	   adaption power calculation. */
+
+	{
+		int new, old;
+
+		/* efficient "out with the old and in with the new" algorithm so
+		   we don't have to recalculate over the whole block of
+		   samples. */
+		new = (int)tx *(int)tx;
+		old = (int)ec->fir_state.history[ec->fir_state.curr_pos] *
+		    (int)ec->fir_state.history[ec->fir_state.curr_pos];
+		ec->Pstates +=
+		    ((new - old) + (1 << ec->log2taps)) >> ec->log2taps;
+		if (ec->Pstates < 0)
+			ec->Pstates = 0;
 	}
+
+	/* Calculate short term average levels using simple single pole IIRs */
+
+	ec->Ltxacc += abs(tx) - ec->Ltx;
+	ec->Ltx = (ec->Ltxacc + (1 << 4)) >> 5;
+	ec->Lrxacc += abs(rx) - ec->Lrx;
+	ec->Lrx = (ec->Lrxacc + (1 << 4)) >> 5;
+
+	/* Foreground filter --------------------------------------------------- */
+
+	ec->fir_state.coeffs = ec->fir_taps16[0];
+	echo_value = fir16(&ec->fir_state, tx);
+	ec->clean = rx - echo_value;
+	ec->Lcleanacc += abs(ec->clean) - ec->Lclean;
+	ec->Lclean = (ec->Lcleanacc + (1 << 4)) >> 5;
+
+	/* Background filter --------------------------------------------------- */
+
+	echo_value = fir16(&ec->fir_state_bg, tx);
+	clean_bg = rx - echo_value;
+	ec->Lclean_bgacc += abs(clean_bg) - ec->Lclean_bg;
+	ec->Lclean_bg = (ec->Lclean_bgacc + (1 << 4)) >> 5;
+
+	/* Background Filter adaption ----------------------------------------- */
+
+	/* Almost always adap bg filter, just simple DT and energy
+	   detection to minimise adaption in cases of strong double talk.
+	   However this is not critical for the dual path algorithm.
+	 */
+	ec->factor = 0;
+	ec->shift = 0;
+	if ((ec->nonupdate_dwell == 0)) {
+		int P, logP, shift;
+
+		/* Determine:
+
+		   f = Beta * clean_bg_rx/P ------ (1)
+
+		   where P is the total power in the filter states.
+
+		   The Boffins have shown that if we obey (1) we converge
+		   quickly and avoid instability.
+
+		   The correct factor f must be in Q30, as this is the fixed
+		   point format required by the lms_adapt_bg() function,
+		   therefore the scaled version of (1) is:
+
+		   (2^30) * f  = (2^30) * Beta * clean_bg_rx/P
+		   factor  = (2^30) * Beta * clean_bg_rx/P         ----- (2)
+
+		   We have chosen Beta = 0.25 by experiment, so:
+
+		   factor  = (2^30) * (2^-2) * clean_bg_rx/P
+
+		   (30 - 2 - log2(P))
+		   factor  = clean_bg_rx 2                         ----- (3)
+
+		   To avoid a divide we approximate log2(P) as top_bit(P),
+		   which returns the position of the highest non-zero bit in
+		   P.  This approximation introduces an error as large as a
+		   factor of 2, but the algorithm seems to handle it OK.
+
+		   Come to think of it a divide may not be a big deal on a
+		   modern DSP, so its probably worth checking out the cycles
+		   for a divide versus a top_bit() implementation.
+		 */
+
+		P = MIN_TX_POWER_FOR_ADAPTION + ec->Pstates;
+		logP = top_bit(P) + ec->log2taps;
+		shift = 30 - 2 - logP;
+		ec->shift = shift;
+
+		lms_adapt_bg(ec, clean_bg, shift);
+	}
+
+	/* very simple DTD to make sure we dont try and adapt with strong
+	   near end speech */
+
+	ec->adapt = 0;
+	if ((ec->Lrx > MIN_RX_POWER_FOR_ADAPTION) && (ec->Lrx > ec->Ltx))
+		ec->nonupdate_dwell = DTD_HANGOVER;
+	if (ec->nonupdate_dwell)
+		ec->nonupdate_dwell--;
+
+	/* Transfer logic ------------------------------------------------------ */
+
+	/* These conditions are from the dual path paper [1], I messed with
+	   them a bit to improve performance. */
+
+	if ((ec->adaption_mode & ECHO_CAN_USE_ADAPTION) &&
+	    (ec->nonupdate_dwell == 0) &&
+	    (8 * ec->Lclean_bg <
+	     7 * ec->Lclean) /* (ec->Lclean_bg < 0.875*ec->Lclean) */ &&
+	    (8 * ec->Lclean_bg <
+	     ec->Ltx) /* (ec->Lclean_bg < 0.125*ec->Ltx)    */ ) {
+		if (ec->cond_met == 6) {
+			/* BG filter has had better results for 6 consecutive samples */
+			ec->adapt = 1;
+			memcpy(ec->fir_taps16[0], ec->fir_taps16[1],
+			       ec->taps * sizeof(int16_t));
+		} else
+			ec->cond_met++;
+	} else
+		ec->cond_met = 0;
+
+	/* Non-Linear Processing --------------------------------------------------- */
+
+	ec->clean_nlp = ec->clean;
+	if (ec->adaption_mode & ECHO_CAN_USE_NLP) {
+		/* Non-linear processor - a fancy way to say "zap small signals, to avoid
+		   residual echo due to (uLaw/ALaw) non-linearity in the channel.". */
+
+		if ((16 * ec->Lclean < ec->Ltx)) {
+			/* Our e/c has improved echo by at least 24 dB (each factor of 2 is 6dB,
+			   so 2*2*2*2=16 is the same as 6+6+6+6=24dB) */
+			if (ec->adaption_mode & ECHO_CAN_USE_CNG) {
+				ec->cng_level = ec->Lbgn;
+
+				/* Very elementary comfort noise generation.  Just random
+				   numbers rolled off very vaguely Hoth-like.  DR: This
+				   noise doesn't sound quite right to me - I suspect there
+				   are some overlfow issues in the filtering as it's too
+				   "crackly".  TODO: debug this, maybe just play noise at
+				   high level or look at spectrum.
+				 */
+
+				ec->cng_rndnum =
+				    1664525U * ec->cng_rndnum + 1013904223U;
+				ec->cng_filter =
+				    ((ec->cng_rndnum & 0xFFFF) - 32768 +
+				     5 * ec->cng_filter) >> 3;
+				ec->clean_nlp =
+				    (ec->cng_filter * ec->cng_level * 8) >> 14;
+
+			} else if (ec->adaption_mode & ECHO_CAN_USE_CLIP) {
+				/* This sounds much better than CNG */
+				if (ec->clean_nlp > ec->Lbgn)
+					ec->clean_nlp = ec->Lbgn;
+				if (ec->clean_nlp < -ec->Lbgn)
+					ec->clean_nlp = -ec->Lbgn;
+			} else {
+				/* just mute the residual, doesn't sound very good, used mainly
+				   in G168 tests */
+				ec->clean_nlp = 0;
+			}
+		} else {
+			/* Background noise estimator.  I tried a few algorithms
+			   here without much luck.  This very simple one seems to
+			   work best, we just average the level using a slow (1 sec
+			   time const) filter if the current level is less than a
+			   (experimentally derived) constant.  This means we dont
+			   include high level signals like near end speech.  When
+			   combined with CNG or especially CLIP seems to work OK.
+			 */
+			if (ec->Lclean < 40) {
+				ec->Lbgn_acc += abs(ec->clean) - ec->Lbgn;
+				ec->Lbgn = (ec->Lbgn_acc + (1 << 11)) >> 12;
+			}
+		}
+	}
+
+	/* Roll around the taps buffer */
+	if (ec->curr_pos <= 0)
+		ec->curr_pos = ec->taps;
+	ec->curr_pos--;
+
+	if (ec->adaption_mode & ECHO_CAN_DISABLE)
+		ec->clean_nlp = rx;
+
+	/* Output scaled back up again to match input scaling */
+
+	return (int16_t) ec->clean_nlp << 1;
 }
+
+/* This function is seperated from the echo canceller is it is usually called
+   as part of the tx process.  See rx HP (DC blocking) filter above, it's
+   the same design.
+
+   Some soft phones send speech signals with a lot of low frequency
+   energy, e.g. down to 20Hz.  This can make the hybrid non-linear
+   which causes the echo canceller to fall over.  This filter can help
+   by removing any low frequency before it gets to the tx port of the
+   hybrid.
+
+   It can also help by removing and DC in the tx signal.  DC is bad
+   for LMS algorithms.
+
+   This is one of the classic DC removal filters, adjusted to provide sufficient
+   bass rolloff to meet the above requirement to protect hybrids from things that
+   upset them. The difference between successive samples produces a lousy HPF, and
+   then a suitably placed pole flattens things out. The final result is a nicely
+   rolled off bass end. The filtering is implemented with extended fractional
+   precision, which noise shapes things, giving very clean DC removal.
+*/
+
+int16_t oslec_hpf_tx(struct oslec_state * ec, int16_t tx)
+{
+	int tmp, tmp1;
+
+	if (ec->adaption_mode & ECHO_CAN_USE_TX_HPF) {
+		tmp = tx << 15;
+#if 1
+		/* Make sure the gain of the HPF is 1.0. The first can still saturate a little under
+		   impulse conditions, and it might roll to 32768 and need clipping on sustained peak
+		   level signals. However, the scale of such clipping is small, and the error due to
+		   any saturation should not markedly affect the downstream processing. */
+		tmp -= (tmp >> 4);
 #endif
+		ec->tx_1 += -(ec->tx_1 >> DC_LOG2BETA) + tmp - ec->tx_2;
+		tmp1 = ec->tx_1 >> 15;
+		if (tmp1 > 32767)
+			tmp1 = 32767;
+		if (tmp1 < -32767)
+			tmp1 = -32767;
+		tx = tmp1;
+		ec->tx_2 = tmp;
+	}
+
+	return tx;
+}
 
 static int __init mod_init(void)
 {
@@ -149,8 +720,7 @@
 		return -EPERM;
 	}
 
-	module_printk(KERN_INFO, "Registered echo canceler '%s'\n",
-		my_factory.get_name(NULL));
+	module_printk(KERN_INFO, "Registered echo canceler '%s'\n", name);
 
 	return 0;
 }
@@ -160,9 +730,9 @@
 	dahdi_unregister_echocan_factory(&my_factory);
 }
 
-MODULE_DESCRIPTION("DAHDI OSLEC wrapper");
-MODULE_AUTHOR("Tzafrir Cohen <tzafrir.cohen@xorcom.com>");
-MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("DAHDI 'OSLEC' Echo Canceler");
+MODULE_AUTHOR("Eric Wilde <ewilde@bsmdevelopment.com>");
+MODULE_LICENSE("GPL v2");
 
 module_init(mod_init);
 module_exit(mod_exit);
diff -urN dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/echo.h patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/echo.h
--- dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/echo.h	1969-12-31 19:00:00.000000000 -0500
+++ patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/echo.h	2012-05-25 13:39:12.000000000 -0400
@@ -0,0 +1,172 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * echo.c - A line echo canceller.  This code is being developed
+ *          against and partially complies with G168.
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *         and David Rowe <david_at_rowetel_dot_com>
+ *
+ * Copyright (C) 2001 Steve Underwood and 2007 David Rowe
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: echo.h,v 1.9 2006/10/24 13:45:28 steveu Exp $
+ */
+
+#ifndef __ECHO_H
+#define __ECHO_H
+
+/*! \page echo_can_page Line echo cancellation for voice
+
+\section echo_can_page_sec_1 What does it do?
+This module aims to provide G.168-2002 compliant echo cancellation, to remove
+electrical echoes (e.g. from 2-4 wire hybrids) from voice calls.
+
+\section echo_can_page_sec_2 How does it work?
+The heart of the echo cancellor is FIR filter. This is adapted to match the
+echo impulse response of the telephone line. It must be long enough to
+adequately cover the duration of that impulse response. The signal transmitted
+to the telephone line is passed through the FIR filter. Once the FIR is
+properly adapted, the resulting output is an estimate of the echo signal
+received from the line. This is subtracted from the received signal. The result
+is an estimate of the signal which originated at the far end of the line, free
+from echos of our own transmitted signal.
+
+The least mean squares (LMS) algorithm is attributed to Widrow and Hoff, and
+was introduced in 1960. It is the commonest form of filter adaption used in
+things like modem line equalisers and line echo cancellers. There it works very
+well.  However, it only works well for signals of constant amplitude. It works
+very poorly for things like speech echo cancellation, where the signal level
+varies widely.  This is quite easy to fix. If the signal level is normalised -
+similar to applying AGC - LMS can work as well for a signal of varying
+amplitude as it does for a modem signal. This normalised least mean squares
+(NLMS) algorithm is the commonest one used for speech echo cancellation. Many
+other algorithms exist - e.g. RLS (essentially the same as Kalman filtering),
+FAP, etc. Some perform significantly better than NLMS.  However, factors such
+as computational complexity and patents favour the use of NLMS.
+
+A simple refinement to NLMS can improve its performance with speech. NLMS tends
+to adapt best to the strongest parts of a signal. If the signal is white noise,
+the NLMS algorithm works very well. However, speech has more low frequency than
+high frequency content. Pre-whitening (i.e. filtering the signal to flatten its
+spectrum) the echo signal improves the adapt rate for speech, and ensures the
+final residual signal is not heavily biased towards high frequencies. A very
+low complexity filter is adequate for this, so pre-whitening adds little to the
+compute requirements of the echo canceller.
+
+An FIR filter adapted using pre-whitened NLMS performs well, provided certain
+conditions are met:
+
+    - The transmitted signal has poor self-correlation.
+    - There is no signal being generated within the environment being
+      cancelled.
+
+The difficulty is that neither of these can be guaranteed.
+
+If the adaption is performed while transmitting noise (or something fairly
+noise like, such as voice) the adaption works very well. If the adaption is
+performed while transmitting something highly correlative (typically narrow
+band energy such as signalling tones or DTMF), the adaption can go seriously
+wrong. The reason is there is only one solution for the adaption on a near
+random signal - the impulse response of the line. For a repetitive signal,
+there are any number of solutions which converge the adaption, and nothing
+guides the adaption to choose the generalised one. Allowing an untrained
+canceller to converge on this kind of narrowband energy probably a good thing,
+since at least it cancels the tones. Allowing a well converged canceller to
+continue converging on such energy is just a way to ruin its generalised
+adaption. A narrowband detector is needed, so adapation can be suspended at
+appropriate times.
+
+The adaption process is based on trying to eliminate the received signal. When
+there is any signal from within the environment being cancelled it may upset
+the adaption process. Similarly, if the signal we are transmitting is small,
+noise may dominate and disturb the adaption process. If we can ensure that the
+adaption is only performed when we are transmitting a significant signal level,
+and the environment is not, things will be OK. Clearly, it is easy to tell when
+we are sending a significant signal. Telling, if the environment is generating
+a significant signal, and doing it with sufficient speed that the adaption will
+not have diverged too much more we stop it, is a little harder.
+
+The key problem in detecting when the environment is sourcing significant
+energy is that we must do this very quickly. Given a reasonably long sample of
+the received signal, there are a number of strategies which may be used to
+assess whether that signal contains a strong far end component. However, by the
+time that assessment is complete the far end signal will have already caused
+major mis-convergence in the adaption process. An assessment algorithm is
+needed which produces a fairly accurate result from a very short burst of far
+end energy.
+
+\section echo_can_page_sec_3 How do I use it?
+The echo cancellor processes both the transmit and receive streams sample by
+sample. The processing function is not declared inline. Unfortunately,
+cancellation requires many operations per sample, so the call overhead is only
+a minor burden.
+*/
+
+#include "fir_new.h"
+#include "oslec.h"
+
+/*!
+    G.168 echo canceller descriptor. This defines the working state for a line
+    echo canceller.
+*/
+struct oslec_state {
+	int16_t tx, rx;
+	int16_t clean;
+	int16_t clean_nlp;
+
+	int nonupdate_dwell;
+	int curr_pos;
+	int taps;
+	int log2taps;
+	int adaption_mode;
+
+	int cond_met;
+	int32_t Pstates;
+	int16_t adapt;
+	int32_t factor;
+	int16_t shift;
+
+	/* Average levels and averaging filter states */
+	int Ltxacc, Lrxacc, Lcleanacc, Lclean_bgacc;
+	int Ltx, Lrx;
+	int Lclean;
+	int Lclean_bg;
+	int Lbgn, Lbgn_acc, Lbgn_upper, Lbgn_upper_acc;
+
+	/* foreground and background filter states */
+	fir16_state_t fir_state;
+	fir16_state_t fir_state_bg;
+	int16_t *fir_taps16[2];
+
+	/* DC blocking filter states */
+	int tx_1, tx_2, rx_1, rx_2;
+
+	/* optional High Pass Filter states */
+	int32_t xvtx[5], yvtx[5];
+	int32_t xvrx[5], yvrx[5];
+
+	/* Parameters for the optional Hoth noise generator */
+	int cng_level;
+	int cng_rndnum;
+	int cng_filter;
+
+	/* snapshot sample of coeffs used for development */
+	int16_t *snapshot;
+};
+
+#endif /* __ECHO_H */
diff -urN dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/fir_new.h patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/fir_new.h
--- dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/fir_new.h	1969-12-31 19:00:00.000000000 -0500
+++ patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/fir_new.h	2012-05-25 13:39:12.000000000 -0400
@@ -0,0 +1,295 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * fir.h - General telephony FIR routines
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2002 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: fir.h,v 1.8 2006/10/24 13:45:28 steveu Exp $
+ */
+
+/*! \page fir_page FIR filtering
+\section fir_page_sec_1 What does it do?
+???.
+
+\section fir_page_sec_2 How does it work?
+???.
+*/
+
+#if !defined(_FIR_H_)
+#define _FIR_H_
+
+/*
+   Blackfin NOTES & IDEAS:
+
+   A simple dot product function is used to implement the filter.  This performs
+   just one MAC/cycle which is inefficient but was easy to implement as a first
+   pass.  The current Blackfin code also uses an unrolled form of the filter
+   history to avoid 0 length hardware loop issues.  This is wasteful of
+   memory.
+
+   Ideas for improvement:
+
+   1/ Rewrite filter for dual MAC inner loop.  The issue here is handling
+   history sample offsets that are 16 bit aligned - the dual MAC needs
+   32 bit aligmnent.  There are some good examples in libbfdsp.
+
+   2/ Use the hardware circular buffer facility tohalve memory usage.
+
+   3/ Consider using internal memory.
+
+   Using less memory might also improve speed as cache misses will be
+   reduced. A drop in MIPs and memory approaching 50% should be
+   possible.
+
+   The foreground and background filters currenlty use a total of
+   about 10 MIPs/ch as measured with speedtest.c on a 256 TAP echo
+   can.
+*/
+
+#if defined(USE_MMX)  ||  defined(USE_SSE2)
+#include "mmx.h"
+#endif
+
+/*!
+    16 bit integer FIR descriptor. This defines the working state for a single
+    instance of an FIR filter using 16 bit integer coefficients.
+*/
+typedef struct {
+	int taps;
+	int curr_pos;
+	const int16_t *coeffs;
+	int16_t *history;
+} fir16_state_t;
+
+/*!
+    32 bit integer FIR descriptor. This defines the working state for a single
+    instance of an FIR filter using 32 bit integer coefficients, and filtering
+    16 bit integer data.
+*/
+typedef struct {
+	int taps;
+	int curr_pos;
+	const int32_t *coeffs;
+	int16_t *history;
+} fir32_state_t;
+
+/*!
+    Floating point FIR descriptor. This defines the working state for a single
+    instance of an FIR filter using floating point coefficients and data.
+*/
+typedef struct {
+	int taps;
+	int curr_pos;
+	const float *coeffs;
+	float *history;
+} fir_float_state_t;
+
+static __inline__ const int16_t *fir16_create(fir16_state_t * fir,
+					      const int16_t * coeffs, int taps)
+{
+	fir->taps = taps;
+	fir->curr_pos = taps - 1;
+	fir->coeffs = coeffs;
+#if defined(USE_MMX)  ||  defined(USE_SSE2) || defined(__bfin__)
+	fir->history = kcalloc(2 * taps, sizeof(int16_t), GFP_KERNEL);
+#else
+	fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
+#endif
+	return fir->history;
+}
+
+static __inline__ void fir16_flush(fir16_state_t * fir)
+{
+#if defined(USE_MMX)  ||  defined(USE_SSE2) || defined(__bfin__)
+	memset(fir->history, 0, 2 * fir->taps * sizeof(int16_t));
+#else
+	memset(fir->history, 0, fir->taps * sizeof(int16_t));
+#endif
+}
+
+static __inline__ void fir16_free(fir16_state_t * fir)
+{
+	kfree(fir->history);
+}
+
+#ifdef __bfin__
+static inline int32_t dot_asm(short *x, short *y, int len)
+{
+	int dot;
+
+	len--;
+
+	__asm__("I0 = %1;\n\t"
+		"I1 = %2;\n\t"
+		"A0 = 0;\n\t"
+		"R0.L = W[I0++] || R1.L = W[I1++];\n\t"
+		"LOOP dot%= LC0 = %3;\n\t"
+		"LOOP_BEGIN dot%=;\n\t"
+		"A0 += R0.L * R1.L (IS) || R0.L = W[I0++] || R1.L = W[I1++];\n\t"
+		"LOOP_END dot%=;\n\t"
+		"A0 += R0.L*R1.L (IS);\n\t"
+		"R0 = A0;\n\t"
+		"%0 = R0;\n\t"
+		:"=&d"(dot)
+		:"a"(x), "a"(y), "a"(len)
+		:"I0", "I1", "A1", "A0", "R0", "R1"
+	);
+
+	return dot;
+}
+#endif
+
+static __inline__ int16_t fir16(fir16_state_t * fir, int16_t sample)
+{
+	int32_t y;
+#if defined(USE_MMX)
+	int i;
+	mmx_t *mmx_coeffs;
+	mmx_t *mmx_hist;
+
+	fir->history[fir->curr_pos] = sample;
+	fir->history[fir->curr_pos + fir->taps] = sample;
+
+	mmx_coeffs = (mmx_t *) fir->coeffs;
+	mmx_hist = (mmx_t *) & fir->history[fir->curr_pos];
+	i = fir->taps;
+	pxor_r2r(mm4, mm4);
+	/* 8 samples per iteration, so the filter must be a multiple of 8 long. */
+	while (i > 0) {
+		movq_m2r(mmx_coeffs[0], mm0);
+		movq_m2r(mmx_coeffs[1], mm2);
+		movq_m2r(mmx_hist[0], mm1);
+		movq_m2r(mmx_hist[1], mm3);
+		mmx_coeffs += 2;
+		mmx_hist += 2;
+		pmaddwd_r2r(mm1, mm0);
+		pmaddwd_r2r(mm3, mm2);
+		paddd_r2r(mm0, mm4);
+		paddd_r2r(mm2, mm4);
+		i -= 8;
+	}
+	movq_r2r(mm4, mm0);
+	psrlq_i2r(32, mm0);
+	paddd_r2r(mm0, mm4);
+	movd_r2m(mm4, y);
+	emms();
+#elif defined(USE_SSE2)
+	int i;
+	xmm_t *xmm_coeffs;
+	xmm_t *xmm_hist;
+
+	fir->history[fir->curr_pos] = sample;
+	fir->history[fir->curr_pos + fir->taps] = sample;
+
+	xmm_coeffs = (xmm_t *) fir->coeffs;
+	xmm_hist = (xmm_t *) & fir->history[fir->curr_pos];
+	i = fir->taps;
+	pxor_r2r(xmm4, xmm4);
+	/* 16 samples per iteration, so the filter must be a multiple of 16 long. */
+	while (i > 0) {
+		movdqu_m2r(xmm_coeffs[0], xmm0);
+		movdqu_m2r(xmm_coeffs[1], xmm2);
+		movdqu_m2r(xmm_hist[0], xmm1);
+		movdqu_m2r(xmm_hist[1], xmm3);
+		xmm_coeffs += 2;
+		xmm_hist += 2;
+		pmaddwd_r2r(xmm1, xmm0);
+		pmaddwd_r2r(xmm3, xmm2);
+		paddd_r2r(xmm0, xmm4);
+		paddd_r2r(xmm2, xmm4);
+		i -= 16;
+	}
+	movdqa_r2r(xmm4, xmm0);
+	psrldq_i2r(8, xmm0);
+	paddd_r2r(xmm0, xmm4);
+	movdqa_r2r(xmm4, xmm0);
+	psrldq_i2r(4, xmm0);
+	paddd_r2r(xmm0, xmm4);
+	movd_r2m(xmm4, y);
+#elif defined(__bfin__)
+	fir->history[fir->curr_pos] = sample;
+	fir->history[fir->curr_pos + fir->taps] = sample;
+	y = dot_asm((int16_t *) fir->coeffs, &fir->history[fir->curr_pos],
+		    fir->taps);
+#else
+	int i;
+	int offset1;
+	int offset2;
+
+	fir->history[fir->curr_pos] = sample;
+
+	offset2 = fir->curr_pos;
+	offset1 = fir->taps - offset2;
+	y = 0;
+	for (i = fir->taps - 1; i >= offset1; i--)
+		y += fir->coeffs[i] * fir->history[i - offset1];
+	for (; i >= 0; i--)
+		y += fir->coeffs[i] * fir->history[i + offset2];
+#endif
+	if (fir->curr_pos <= 0)
+		fir->curr_pos = fir->taps;
+	fir->curr_pos--;
+	return (int16_t) (y >> 15);
+}
+
+static __inline__ const int16_t *fir32_create(fir32_state_t * fir,
+					      const int32_t * coeffs, int taps)
+{
+	fir->taps = taps;
+	fir->curr_pos = taps - 1;
+	fir->coeffs = coeffs;
+	fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
+	return fir->history;
+}
+
+static __inline__ void fir32_flush(fir32_state_t * fir)
+{
+	memset(fir->history, 0, fir->taps * sizeof(int16_t));
+}
+
+static __inline__ void fir32_free(fir32_state_t * fir)
+{
+	kfree(fir->history);
+}
+
+static __inline__ int16_t fir32(fir32_state_t * fir, int16_t sample)
+{
+	int i;
+	int32_t y;
+	int offset1;
+	int offset2;
+
+	fir->history[fir->curr_pos] = sample;
+	offset2 = fir->curr_pos;
+	offset1 = fir->taps - offset2;
+	y = 0;
+	for (i = fir->taps - 1; i >= offset1; i--)
+		y += fir->coeffs[i] * fir->history[i - offset1];
+	for (; i >= 0; i--)
+		y += fir->coeffs[i] * fir->history[i + offset2];
+	if (fir->curr_pos <= 0)
+		fir->curr_pos = fir->taps;
+	fir->curr_pos--;
+	return (int16_t) (y >> 15);
+}
+
+#endif
+/*- End of file ------------------------------------------------------------*/
diff -urN dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/Kbuild patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/Kbuild
--- dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/Kbuild	2011-11-15 01:44:09.000000000 -0500
+++ patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/Kbuild	2012-05-25 13:39:50.000000000 -0400
@@ -37,7 +37,7 @@
 
 # Only enable this if you think you know what you're doing. This is not
 # supported yet:
-#obj-m += dahdi_echocan_oslec.o
+obj-m += dahdi_echocan_oslec.o
 #
 # A quick and dirty way to build OSLEC, if you happened to place it
 # yourself in the dahdi source tree. This is experimental. See README
diff -urN dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/oslec.h patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/oslec.h
--- dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/oslec.h	1969-12-31 19:00:00.000000000 -0500
+++ patched-dahdi-linux-complete-2.5.0.1+2.5.0.1/linux/drivers/dahdi/oslec.h	2012-05-25 13:39:12.000000000 -0400
@@ -0,0 +1,86 @@
+/*
+ *  OSLEC - A line echo canceller.  This code is being developed
+ *          against and partially complies with G168. Using code from SpanDSP
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *         and David Rowe <david_at_rowetel_dot_com>
+ *
+ * Copyright (C) 2001 Steve Underwood and 2007-2008 David Rowe
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#ifndef __OSLEC_H
+#define __OSLEC_H
+
+/* TODO: document interface */
+
+/* Mask bits for the adaption mode */
+#define ECHO_CAN_USE_ADAPTION	0x01
+#define ECHO_CAN_USE_NLP	0x02
+#define ECHO_CAN_USE_CNG	0x04
+#define ECHO_CAN_USE_CLIP	0x08
+#define ECHO_CAN_USE_TX_HPF	0x10
+#define ECHO_CAN_USE_RX_HPF	0x20
+#define ECHO_CAN_DISABLE	0x40
+
+/*!
+    G.168 echo canceller descriptor. This defines the working state for a line
+    echo canceller.
+*/
+struct oslec_state;
+
+/*! Create a voice echo canceller context.
+    \param len The length of the canceller, in samples.
+    \return The new canceller context, or NULL if the canceller could not be created.
+*/
+struct oslec_state *oslec_create(int len, int adaption_mode);
+
+/*! Free a voice echo canceller context.
+    \param ec The echo canceller context.
+*/
+void oslec_free(struct oslec_state *ec);
+
+/*! Flush (reinitialise) a voice echo canceller context.
+    \param ec The echo canceller context.
+*/
+void oslec_flush(struct oslec_state *ec);
+
+/*! Set the adaption mode of a voice echo canceller context.
+    \param ec The echo canceller context.
+    \param adapt The mode.
+*/
+void oslec_adaption_mode(struct oslec_state *ec, int adaption_mode);
+
+void oslec_snapshot(struct oslec_state *ec);
+
+/*! Process a sample through a voice echo canceller.
+    \param ec The echo canceller context.
+    \param tx The transmitted audio sample.
+    \param rx The received audio sample.
+    \return The clean (echo cancelled) received sample.
+*/
+int16_t oslec_update(struct oslec_state *ec, int16_t tx, int16_t rx);
+
+/*! Process to high pass filter the tx signal.
+    \param ec The echo canceller context.
+    \param tx The transmitted auio sample.
+    \return The HP filtered transmit sample, send this to your D/A.
+*/
+int16_t oslec_hpf_tx(struct oslec_state *ec, int16_t tx);
+
+#endif /* __OSLEC_H */
