codec_dahdi.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * DAHDI native transcoding support
 *
 * Copyright (C) 1999 - 2008, Digium, Inc.
 *
 * Mark Spencer <[email protected]>
 * Kevin P. Fleming <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Translate between various formats natively through DAHDI transcoding
 *
 * \ingroup codecs
 */

/*** MODULEINFO
 <depend>dahdi</depend>
 <support_level>core</support_level>
 ***/

#include "asterisk.h"
#include <stdbool.h>

#include <poll.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <dahdi/user.h>

#include "asterisk/lock.h"
#include "asterisk/translate.h"
#include "asterisk/config.h"
#include "asterisk/module.h"
#include "asterisk/cli.h"
#include "asterisk/channel.h"
#include "asterisk/utils.h"
#include "asterisk/linkedlists.h"
#include "asterisk/ulaw.h"
#include "asterisk/format_compatibility.h"

#define BUFFER_SIZE 8000

#define G723_SAMPLES 240
#define G729_SAMPLES 160
#define ULAW_SAMPLES 160

/* Defines from DAHDI. */
#ifndef DAHDI_FORMAT_MAX_AUDIO
/*! G.723.1 compression */
#define DAHDI_FORMAT_G723_1 (1 << 0)
/*! GSM compression */
#define DAHDI_FORMAT_GSM (1 << 1)
/*! Raw mu-law data (G.711) */
#define DAHDI_FORMAT_ULAW (1 << 2)
/*! Raw A-law data (G.711) */
#define DAHDI_FORMAT_ALAW (1 << 3)
/*! ADPCM (G.726, 32kbps) */
#define DAHDI_FORMAT_G726 (1 << 4)
/*! ADPCM (IMA) */
#define DAHDI_FORMAT_ADPCM (1 << 5)
/*! Raw 16-bit Signed Linear (8000 Hz) PCM */
#define DAHDI_FORMAT_SLINEAR (1 << 6)
/*! LPC10, 180 samples/frame */
#define DAHDI_FORMAT_LPC10 (1 << 7)
/*! G.729A audio */
#define DAHDI_FORMAT_G729A (1 << 8)
/*! SpeeX Free Compression */
#define DAHDI_FORMAT_SPEEX (1 << 9)
/*! iLBC Free Compression */
#define DAHDI_FORMAT_ILBC (1 << 10)
#endif

static struct channel_usage {
 int total;
 int encoders;
 int decoders;
} channels;

#if defined(NOT_NEEDED)
/*!
 * \internal
 * \brief Convert DAHDI format bitfield to old Asterisk format bitfield.
 * \since 13.0.0
 *
 * \param dahdi Bitfield from DAHDI to convert.
 *
 * \note They should be the same values but they don't have to be.
 *
 * \return Old Asterisk bitfield equivalent.
 */
static uint64_t bitfield_dahdi2ast(unsigned dahdi)
{
 uint64_t ast;

 switch (dahdi) {
 case DAHDI_FORMAT_G723_1:
 ast = AST_FORMAT_G723;
 break;
 case DAHDI_FORMAT_GSM:
 ast = AST_FORMAT_GSM;
 break;
 case DAHDI_FORMAT_ULAW:
 ast = AST_FORMAT_ULAW;
 break;
 case DAHDI_FORMAT_ALAW:
 ast = AST_FORMAT_ALAW;
 break;
 case DAHDI_FORMAT_G726:
 ast = AST_FORMAT_G726_AAL2;
 break;
 case DAHDI_FORMAT_ADPCM:
 ast = AST_FORMAT_ADPCM;
 break;
 case DAHDI_FORMAT_SLINEAR:
 ast = AST_FORMAT_SLIN;
 break;
 case DAHDI_FORMAT_LPC10:
 ast = AST_FORMAT_LPC10;
 break;
 case DAHDI_FORMAT_G729A:
 ast = AST_FORMAT_G729;
 break;
 case DAHDI_FORMAT_SPEEX:
 ast = AST_FORMAT_SPEEX;
 break;
 case DAHDI_FORMAT_ILBC:
 ast = AST_FORMAT_ILBC;
 break;
 default:
 ast = 0;
 break;
 }

 return ast;
}
#endif /* defined(NOT_NEEDED) */

/*!
 * \internal
 * \brief Get the ast_codec by DAHDI format.
 * \since 13.0.0
 *
 * \param dahdi_fmt DAHDI specific codec identifier.
 *
 * \return Specified codec if exists otherwise NULL.
 */
static const struct ast_codec *get_dahdi_codec(uint32_t dahdi_fmt)
{
 const struct ast_codec *codec;

 static const struct ast_codec dahdi_g723_1 = {
 .name = "g723",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_gsm = {
 .name = "gsm",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_ulaw = {
 .name = "ulaw",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_alaw = {
 .name = "alaw",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_g726 = {
 .name = "g726",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_adpcm = {
 .name = "adpcm",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_slinear = {
 .name = "slin",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_lpc10 = {
 .name = "lpc10",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_g729a = {
 .name = "g729",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_speex = {
 .name = "speex",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };
 static const struct ast_codec dahdi_ilbc = {
 .name = "ilbc",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 };

 switch (dahdi_fmt) {
 case DAHDI_FORMAT_G723_1:
 codec = &dahdi_g723_1;
 break;
 case DAHDI_FORMAT_GSM:
 codec = &dahdi_gsm;
 break;
 case DAHDI_FORMAT_ULAW:
 codec = &dahdi_ulaw;
 break;
 case DAHDI_FORMAT_ALAW:
 codec = &dahdi_alaw;
 break;
 case DAHDI_FORMAT_G726:
 codec = &dahdi_g726;
 break;
 case DAHDI_FORMAT_ADPCM:
 codec = &dahdi_adpcm;
 break;
 case DAHDI_FORMAT_SLINEAR:
 codec = &dahdi_slinear;
 break;
 case DAHDI_FORMAT_LPC10:
 codec = &dahdi_lpc10;
 break;
 case DAHDI_FORMAT_G729A:
 codec = &dahdi_g729a;
 break;
 case DAHDI_FORMAT_SPEEX:
 codec = &dahdi_speex;
 break;
 case DAHDI_FORMAT_ILBC:
 codec = &dahdi_ilbc;
 break;
 default:
 codec = NULL;
 break;
 }

 return codec;
}

static char *handle_cli_transcoder_show(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a);

static struct ast_cli_entry cli[] = {
 AST_CLI_DEFINE(handle_cli_transcoder_show, "Display DAHDI transcoder utilization.")
};

struct translator {
 struct ast_translator t;
 uint32_t src_dahdi_fmt;
 uint32_t dst_dahdi_fmt;
 AST_LIST_ENTRY(translator) entry;
};

#ifndef container_of
#define container_of(ptr, type, member) \
 ((type *)((char *)(ptr) - offsetof(type, member)))
#endif

static AST_LIST_HEAD_STATIC(translators, translator);

struct codec_dahdi_pvt {
 int fd;
 struct dahdi_transcoder_formats fmts;
 unsigned int softslin:1;
 unsigned int fake:2;
 uint16_t required_samples;
 uint16_t samples_in_buffer;
 uint16_t samples_written_to_hardware;
 uint8_t ulaw_buffer[1024];
};

/* Only used by a decoder */
static int ulawtolin(struct ast_trans_pvt *pvt, int samples)
{
 struct codec_dahdi_pvt *dahdip = pvt->pvt;
 int i = samples;
 uint8_t *src = &dahdip->ulaw_buffer[0];
 int16_t *dst = pvt->outbuf.i16 + pvt->datalen;

 /* convert and copy in outbuf */
 while (i--) {
 *dst++ = AST_MULAW(*src++);
 }

 return 0;
}

/* Only used by an encoder. */
static int lintoulaw(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
 struct codec_dahdi_pvt *dahdip = pvt->pvt;
 int i = f->samples;
 uint8_t *dst = &dahdip->ulaw_buffer[dahdip->samples_in_buffer];
 int16_t *src = f->data.ptr;

 if (dahdip->samples_in_buffer + i > sizeof(dahdip->ulaw_buffer)) {
 ast_log(LOG_ERROR, "Out of buffer space!\n");
 return -i;
 }

 while (i--) {
 *dst++ = AST_LIN2MU(*src++);
 }

 dahdip->samples_in_buffer += f->samples;
 return 0;
}

static char *handle_cli_transcoder_show(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
 struct channel_usage copy;

 switch (cmd) {
 case CLI_INIT:
 e->command = "transcoder show";
 e->usage =
 "Usage: transcoder show\n"
 " Displays channel utilization of DAHDI transcoder(s).\n";
 return NULL;
 case CLI_GENERATE:
 return NULL;
 }

 if (a->argc != 2)
 return CLI_SHOWUSAGE;

 copy = channels;

 if (copy.total == 0)
 ast_cli(a->fd, "No DAHDI transcoders found.\n");
 else
 ast_cli(a->fd, "%d/%d encoders/decoders of %d channels are in use.\n", copy.encoders, copy.decoders, copy.total);

 return CLI_SUCCESS;
}

static void dahdi_write_frame(struct codec_dahdi_pvt *dahdip, const uint8_t *buffer, const ssize_t count)
{
 int res;
 if (!count) return;
 res = write(dahdip->fd, buffer, count);
 if (-1 == res) {
 ast_log(LOG_ERROR, "Failed to write to transcoder: %s\n", strerror(errno));
 }
 if (count != res) {
 ast_log(LOG_ERROR, "Requested write of %zd bytes, but only wrote %d bytes.\n", count, res);
 }
}

static int dahdi_encoder_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
 struct codec_dahdi_pvt *dahdip = pvt->pvt;

 if (!f->subclass.format) {
 /* We're just faking a return for calculation purposes. */
 dahdip->fake = 2;
 pvt->samples = f->samples;
 return 0;
 }

 /* Buffer up the packets and send them to the hardware if we
 * have enough samples set up. */
 if (dahdip->softslin) {
 if (lintoulaw(pvt, f)) {
 return -1;
 }
 } else {
 /* NOTE: If softslin support is not needed, and the sample
 * size is equal to the required sample size, we wouldn't
 * need this copy operation. But at the time this was
 * written, only softslin is supported. */
 if (dahdip->samples_in_buffer + f->samples > sizeof(dahdip->ulaw_buffer)) {
 ast_log(LOG_ERROR, "Out of buffer space.\n");
 return -1;
 }
 memcpy(&dahdip->ulaw_buffer[dahdip->samples_in_buffer], f->data.ptr, f->samples);
 dahdip->samples_in_buffer += f->samples;
 }

 while (dahdip->samples_in_buffer >= dahdip->required_samples) {
 dahdi_write_frame(dahdip, dahdip->ulaw_buffer, dahdip->required_samples);
 dahdip->samples_written_to_hardware += dahdip->required_samples;
 dahdip->samples_in_buffer -= dahdip->required_samples;
 if (dahdip->samples_in_buffer) {
 /* Shift any remaining bytes down. */
 memmove(dahdip->ulaw_buffer, &dahdip->ulaw_buffer[dahdip->required_samples],
 dahdip->samples_in_buffer);
 }
 }
 pvt->samples += f->samples;
 pvt->datalen = 0;
 return -1;
}

static void dahdi_wait_for_packet(int fd)
{
 struct pollfd p = {0};
 p.fd = fd;
 p.events = POLLIN;
 poll(&p, 1, 10);
}

static struct ast_frame *dahdi_encoder_frameout(struct ast_trans_pvt *pvt)
{
 struct codec_dahdi_pvt *dahdip = pvt->pvt;
 int res;

 if (2 == dahdip->fake) {
 struct ast_frame frm = {
 .frametype = AST_FRAME_VOICE,
 .samples = dahdip->required_samples,
 .src = pvt->t->name,
 };

 dahdip->fake = 1;
 pvt->samples = 0;

 return ast_frisolate(&frm);
 } else if (1 == dahdip->fake) {
 dahdip->fake = 0;
 return NULL;
 }

 if (dahdip->samples_written_to_hardware >= dahdip->required_samples) {
 dahdi_wait_for_packet(dahdip->fd);
 }

 res = read(dahdip->fd, pvt->outbuf.c + pvt->datalen, pvt->t->buf_size - pvt->datalen);
 if (-1 == res) {
 if (EWOULDBLOCK == errno) {
 /* Nothing waiting... */
 return NULL;
 } else {
 ast_log(LOG_ERROR, "Failed to read from transcoder: %s\n", strerror(errno));
 return NULL;
 }
 } else {
 pvt->f.datalen = res;
 pvt->f.samples = ast_codec_samples_count(&pvt->f);

 dahdip->samples_written_to_hardware =
 (dahdip->samples_written_to_hardware >= pvt->f.samples) ?
 dahdip->samples_written_to_hardware - pvt->f.samples : 0;

 pvt->samples = 0;
 pvt->datalen = 0;
 return ast_frisolate(&pvt->f);
 }

 /* Shouldn't get here... */
 return NULL;
}

static int dahdi_decoder_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
 struct codec_dahdi_pvt *dahdip = pvt->pvt;

 if (!f->subclass.format) {
 /* We're just faking a return for calculation purposes. */
 dahdip->fake = 2;
 pvt->samples = f->samples;
 return 0;
 }

 if (!f->datalen) {
 if (f->samples != dahdip->required_samples) {
 ast_log(LOG_ERROR, "%d != %d %d\n", f->samples, dahdip->required_samples, f->datalen);
 }
 }
 dahdi_write_frame(dahdip, f->data.ptr, f->datalen);
 dahdip->samples_written_to_hardware += f->samples;
 pvt->samples += f->samples;
 pvt->datalen = 0;
 return -1;
}

static struct ast_frame *dahdi_decoder_frameout(struct ast_trans_pvt *pvt)
{
 int res;
 struct codec_dahdi_pvt *dahdip = pvt->pvt;

 if (2 == dahdip->fake) {
 struct ast_frame frm = {
 .frametype = AST_FRAME_VOICE,
 .samples = dahdip->required_samples,
 .src = pvt->t->name,
 };

 dahdip->fake = 1;
 pvt->samples = 0;

 return ast_frisolate(&frm);
 } else if (1 == dahdip->fake) {
 pvt->samples = 0;
 dahdip->fake = 0;
 return NULL;
 }

 if (dahdip->samples_written_to_hardware >= ULAW_SAMPLES) {
 dahdi_wait_for_packet(dahdip->fd);
 }

 /* Let's check to see if there is a new frame for us.... */
 if (dahdip->softslin) {
 res = read(dahdip->fd, dahdip->ulaw_buffer, sizeof(dahdip->ulaw_buffer));
 } else {
 res = read(dahdip->fd, pvt->outbuf.c + pvt->datalen, pvt->t->buf_size - pvt->datalen);
 }

 if (-1 == res) {
 if (EWOULDBLOCK == errno) {
 /* Nothing waiting... */
 return NULL;
 } else {
 ast_log(LOG_ERROR, "Failed to read from transcoder: %s\n", strerror(errno));
 return NULL;
 }
 } else {
 if (dahdip->softslin) {
 ulawtolin(pvt, res);
 pvt->f.datalen = res * 2;
 } else {
 pvt->f.datalen = res;
 }
 pvt->datalen = 0;
 pvt->f.samples = res;
 pvt->samples = 0;
 dahdip->samples_written_to_hardware =
 (dahdip->samples_written_to_hardware >= res) ?
 dahdip->samples_written_to_hardware - res : 0;

 return ast_frisolate(&pvt->f);
 }

 /* Shouldn't get here... */
 return NULL;
}


static void dahdi_destroy(struct ast_trans_pvt *pvt)
{
 struct codec_dahdi_pvt *dahdip = pvt->pvt;

 switch (dahdip->fmts.dstfmt) {
 case DAHDI_FORMAT_G729A:
 case DAHDI_FORMAT_G723_1:
 ast_atomic_fetchadd_int(&channels.encoders, -1);
 break;
 default:
 ast_atomic_fetchadd_int(&channels.decoders, -1);
 break;
 }

 close(dahdip->fd);
}

static struct ast_format *dahdi_format_to_cached(int format)
{
 switch (format) {
 case DAHDI_FORMAT_G723_1:
 return ast_format_g723;
 case DAHDI_FORMAT_GSM:
 return ast_format_gsm;
 case DAHDI_FORMAT_ULAW:
 return ast_format_ulaw;
 case DAHDI_FORMAT_ALAW:
 return ast_format_alaw;
 case DAHDI_FORMAT_G726:
 return ast_format_g726;
 case DAHDI_FORMAT_ADPCM:
 return ast_format_adpcm;
 case DAHDI_FORMAT_SLINEAR:
 return ast_format_slin;
 case DAHDI_FORMAT_LPC10:
 return ast_format_lpc10;
 case DAHDI_FORMAT_G729A:
 return ast_format_g729;
 case DAHDI_FORMAT_SPEEX:
 return ast_format_speex;
 case DAHDI_FORMAT_ILBC:
 return ast_format_ilbc;
 }

 /* This will never be reached */
 ast_assert(0);
 return NULL;
}

static int dahdi_translate(struct ast_trans_pvt *pvt, uint32_t dst_dahdi_fmt, uint32_t src_dahdi_fmt)
{
 /* Request translation through zap if possible */
 int fd;
 struct codec_dahdi_pvt *dahdip = pvt->pvt;
 int tried_once = 0;
 const char *dev_filename = "/dev/dahdi/transcode";

 if ((fd = open(dev_filename, O_RDWR)) < 0) {
 ast_log(LOG_ERROR, "Failed to open %s: %s\n", dev_filename, strerror(errno));
 return -1;
 }

 dahdip->fmts.srcfmt = src_dahdi_fmt;
 dahdip->fmts.dstfmt = dst_dahdi_fmt;

 ast_assert(pvt->f.subclass.format == NULL);
 pvt->f.subclass.format = ao2_bump(dahdi_format_to_cached(dahdip->fmts.dstfmt));

 ast_debug(1, "Opening transcoder channel from %s to %s.\n", pvt->t->src_codec.name, pvt->t->dst_codec.name);

retry:
 if (ioctl(fd, DAHDI_TC_ALLOCATE, &dahdip->fmts)) {
 if ((ENODEV == errno) && !tried_once) {
 /* We requested to translate to/from an unsupported
 * format. Most likely this is because signed linear
 * was not supported by any hardware devices even
 * though this module always registers signed linear
 * support. In this case we'll retry, requesting
 * support for ULAW instead of signed linear and then
 * we'll just convert from ulaw to signed linear in
 * software. */
 if (dahdip->fmts.srcfmt == DAHDI_FORMAT_SLINEAR) {
 ast_debug(1, "Using soft_slin support on source\n");
 dahdip->softslin = 1;
 dahdip->fmts.srcfmt = DAHDI_FORMAT_ULAW;
 } else if (dahdip->fmts.dstfmt == DAHDI_FORMAT_SLINEAR) {
 ast_debug(1, "Using soft_slin support on destination\n");
 dahdip->softslin = 1;
 dahdip->fmts.dstfmt = DAHDI_FORMAT_ULAW;
 }
 tried_once = 1;
 goto retry;
 }
 ast_log(LOG_ERROR, "Unable to attach to transcoder: %s\n", strerror(errno));
 close(fd);

 return -1;
 }

 ast_fd_set_flags(fd, O_NONBLOCK);

 dahdip->fd = fd;

 dahdip->required_samples = ((dahdip->fmts.dstfmt|dahdip->fmts.srcfmt) & (DAHDI_FORMAT_G723_1)) ? G723_SAMPLES : G729_SAMPLES;

 switch (dahdip->fmts.dstfmt) {
 case DAHDI_FORMAT_G729A:
 ast_atomic_fetchadd_int(&channels.encoders, +1);
 break;
 case DAHDI_FORMAT_G723_1:
 ast_atomic_fetchadd_int(&channels.encoders, +1);
 break;
 default:
 ast_atomic_fetchadd_int(&channels.decoders, +1);
 break;
 }

 return 0;
}

static int dahdi_new(struct ast_trans_pvt *pvt)
{
 struct translator *zt = container_of(pvt->t, struct translator, t);

 return dahdi_translate(pvt, zt->dst_dahdi_fmt, zt->src_dahdi_fmt);
}

static struct ast_frame *fakesrc_sample(void)
{
 /* Don't bother really trying to test hardware ones. */
 static struct ast_frame f = {
 .frametype = AST_FRAME_VOICE,
 .samples = 160,
 .src = __PRETTY_FUNCTION__
 };

 return &f;
}

static bool is_encoder(uint32_t src_dahdi_fmt)
{
 return ((src_dahdi_fmt & (DAHDI_FORMAT_ULAW | DAHDI_FORMAT_ALAW | DAHDI_FORMAT_SLINEAR)) > 0);
}

/* Must be called with the translators list locked. */
static int register_translator(uint32_t dst_dahdi_fmt, uint32_t src_dahdi_fmt)
{
 const struct ast_codec *dst_codec;
 const struct ast_codec *src_codec;
 struct translator *zt;
 int res;

 dst_codec = get_dahdi_codec(dst_dahdi_fmt);
 src_codec = get_dahdi_codec(src_dahdi_fmt);
 if (!dst_codec || !src_codec) {
 return -1;
 }

 if (!(zt = ast_calloc(1, sizeof(*zt)))) {
 return -1;
 }

 zt->src_dahdi_fmt = src_dahdi_fmt;
 zt->dst_dahdi_fmt = dst_dahdi_fmt;

 snprintf(zt->t.name, sizeof(zt->t.name), "dahdi_%s_to_%s",
 src_codec->name, dst_codec->name);

 memcpy(&zt->t.src_codec, src_codec, sizeof(*src_codec));
 memcpy(&zt->t.dst_codec, dst_codec, sizeof(*dst_codec));
 zt->t.buf_size = BUFFER_SIZE;
 if (is_encoder(src_dahdi_fmt)) {
 zt->t.framein = dahdi_encoder_framein;
 zt->t.frameout = dahdi_encoder_frameout;
 } else {
 zt->t.framein = dahdi_decoder_framein;
 zt->t.frameout = dahdi_decoder_frameout;
 }
 zt->t.destroy = dahdi_destroy;
 zt->t.buffer_samples = 0;
 zt->t.newpvt = dahdi_new;
 zt->t.sample = fakesrc_sample;
 zt->t.native_plc = 0;

 zt->t.desc_size = sizeof(struct codec_dahdi_pvt);
 if ((res = ast_register_translator(&zt->t))) {
 ast_free(zt);
 return -1;
 }

 AST_LIST_INSERT_HEAD(&translators, zt, entry);

 return res;
}

static void unregister_translators(void)
{
 struct translator *cur;

 AST_LIST_LOCK(&translators);
 while ((cur = AST_LIST_REMOVE_HEAD(&translators, entry))) {
 ast_unregister_translator(&cur->t);
 ast_free(cur);
 }
 AST_LIST_UNLOCK(&translators);
}

/* Must be called with the translators list locked. */
static bool is_already_registered(uint32_t dstfmt, uint32_t srcfmt)
{
 bool res = false;
 const struct translator *zt;

 AST_LIST_TRAVERSE(&translators, zt, entry) {
 if ((zt->src_dahdi_fmt == srcfmt) && (zt->dst_dahdi_fmt == dstfmt)) {
 res = true;
 break;
 }
 }

 return res;
}

static void build_translators(uint32_t dstfmts, uint32_t srcfmts)
{
 uint32_t srcfmt;
 uint32_t dstfmt;

 AST_LIST_LOCK(&translators);

 for (srcfmt = 1; srcfmt != 0; srcfmt <<= 1) {
 for (dstfmt = 1; dstfmt != 0; dstfmt <<= 1) {
 if (!(dstfmts & dstfmt) || !(srcfmts & srcfmt)) {
 continue;
 }
 if (is_already_registered(dstfmt, srcfmt)) {
 continue;
 }
 register_translator(dstfmt, srcfmt);
 }
 }

 AST_LIST_UNLOCK(&translators);
}

static int find_transcoders(void)
{
 struct dahdi_transcoder_info info = { 0, };
 int fd;

 if ((fd = open("/dev/dahdi/transcode", O_RDWR)) < 0) {
 ast_log(LOG_ERROR, "Failed to open /dev/dahdi/transcode: %s\n", strerror(errno));
 return 0;
 }

 for (info.tcnum = 0; !ioctl(fd, DAHDI_TC_GETINFO, &info); info.tcnum++) {
 ast_verb(2, "Found transcoder '%s'.\n", info.name);

 /* Complex codecs need to support signed linear. If the
 * hardware transcoder does not natively support signed linear
 * format, we will emulate it in software directly in this
 * module. Also, do not allow direct ulaw/alaw to complex
 * codec translation, since that will prevent the generic PLC
 * functions from working. */
 if (info.dstfmts & (DAHDI_FORMAT_ULAW | DAHDI_FORMAT_ALAW)) {
 info.dstfmts |= DAHDI_FORMAT_SLINEAR;
 info.dstfmts &= ~(DAHDI_FORMAT_ULAW | DAHDI_FORMAT_ALAW);
 }
 if (info.srcfmts & (DAHDI_FORMAT_ULAW | DAHDI_FORMAT_ALAW)) {
 info.srcfmts |= DAHDI_FORMAT_SLINEAR;
 info.srcfmts &= ~(DAHDI_FORMAT_ULAW | DAHDI_FORMAT_ALAW);
 }

 build_translators(info.dstfmts, info.srcfmts);
 ast_atomic_fetchadd_int(&channels.total, info.numchannels / 2);
 }

 close(fd);

 if (!info.tcnum) {
 ast_verb(2, "No hardware transcoders found.\n");
 }

 return 0;
}

static int reload(void)
{
 return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
 ast_cli_unregister_multiple(cli, ARRAY_LEN(cli));
 unregister_translators();

 return 0;
}

static int load_module(void)
{
 find_transcoders();
 ast_cli_register_multiple(cli, ARRAY_LEN(cli));
 return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "Generic DAHDI Transcoder Codec Translator",
 .support_level = AST_MODULE_SUPPORT_CORE,
 .load = load_module,
 .unload = unload_module,
 .reload = reload,
);