chan_oss.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2007, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * FreeBSD changes and multiple device support by Luigi Rizzo, 2005.05.25
 * note-this code best seen with ts=8 (8-spaces tabs) in the editor
 *
 * 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.
 */

// #define HAVE_VIDEO_CONSOLE // uncomment to enable video
/*! \file
 *
 * \brief Channel driver for OSS sound cards
 *
 * \author Mark Spencer <markster@digium.com>
 * \author Luigi Rizzo
 *
 * \par See also
 * \arg \ref Config_oss
 *
 * \ingroup channel_drivers
 */

/*** MODULEINFO
   <depend>ossaudio</depend>
 ***/

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 238497 $")

#include <ctype.h>      /* isalnum() used here */
#include <math.h>
#include <sys/ioctl.h>     

#ifdef __linux
#include <linux/soundcard.h>
#elif defined(__FreeBSD__) || defined(__CYGWIN__)
#include <sys/soundcard.h>
#else
#include <soundcard.h>
#endif

#include "asterisk/channel.h"
#include "asterisk/file.h"
#include "asterisk/callerid.h"
#include "asterisk/module.h"
#include "asterisk/pbx.h"
#include "asterisk/cli.h"
#include "asterisk/causes.h"
#include "asterisk/musiconhold.h"
#include "asterisk/app.h"

#include "console_video.h"

/*! Global jitterbuffer configuration - by default, jb is disabled */
static struct ast_jb_conf default_jbconf =
{
   .flags = 0,
   .max_size = -1,
   .resync_threshold = -1,
   .impl = "",
};
static struct ast_jb_conf global_jbconf;

/*
 * Basic mode of operation:
 *
 * we have one keyboard (which receives commands from the keyboard)
 * and multiple headset's connected to audio cards.
 * Cards/Headsets are named as the sections of oss.conf.
 * The section called [general] contains the default parameters.
 *
 * At any time, the keyboard is attached to one card, and you
 * can switch among them using the command 'console foo'
 * where 'foo' is the name of the card you want.
 *
 * oss.conf parameters are
START_CONFIG

[general]
    ; General config options, with default values shown.
    ; You should use one section per device, with [general] being used
    ; for the first device and also as a template for other devices.
    ;
    ; All but 'debug' can go also in the device-specific sections.
    ;
    ; debug = 0x0    ; misc debug flags, default is 0

    ; Set the device to use for I/O
    ; device = /dev/dsp

    ; Optional mixer command to run upon startup (e.g. to set
    ; volume levels, mutes, etc.
    ; mixer =

    ; Software mic volume booster (or attenuator), useful for sound
    ; cards or microphones with poor sensitivity. The volume level
    ; is in dB, ranging from -20.0 to +20.0
    ; boost = n         ; mic volume boost in dB

    ; Set the callerid for outgoing calls
    ; callerid = John Doe <555-1234>

    ; autoanswer = no      ; no autoanswer on call
    ; autohangup = yes     ; hangup when other party closes
    ; extension = s     ; default extension to call
    ; context = default    ; default context for outgoing calls
    ; language = ""     ; default language

    ; Default Music on Hold class to use when this channel is placed on hold in
    ; the case that the music class is not set on the channel with
    ; Set(CHANNEL(musicclass)=whatever) in the dialplan and the peer channel
    ; putting this one on hold did not suggest a class to use.
    ;
    ; mohinterpret=default

    ; If you set overridecontext to 'yes', then the whole dial string
    ; will be interpreted as an extension, which is extremely useful
    ; to dial SIP, IAX and other extensions which use the '@' character.
    ; The default is 'no' just for backward compatibility, but the
    ; suggestion is to change it.
    ; overridecontext = no ; if 'no', the last @ will start the context
            ; if 'yes' the whole string is an extension.

    ; low level device parameters in case you have problems with the
    ; device driver on your operating system. You should not touch these
    ; unless you know what you are doing.
    ; queuesize = 10    ; frames in device driver
    ; frags = 8         ; argument to SETFRAGMENT

    ;------------------------------ JITTER BUFFER CONFIGURATION --------------------------
    ; jbenable = yes              ; Enables the use of a jitterbuffer on the receiving side of an
                                  ; OSS channel. Defaults to "no". An enabled jitterbuffer will
                                  ; be used only if the sending side can create and the receiving
                                  ; side can not accept jitter. The OSS channel can't accept jitter,
                                  ; thus an enabled jitterbuffer on the receive OSS side will always
                                  ; be used if the sending side can create jitter.

    ; jbmaxsize = 200             ; Max length of the jitterbuffer in milliseconds.

    ; jbresyncthreshold = 1000    ; Jump in the frame timestamps over which the jitterbuffer is
                                  ; resynchronized. Useful to improve the quality of the voice, with
                                  ; big jumps in/broken timestamps, usualy sent from exotic devices
                                  ; and programs. Defaults to 1000.

    ; jbimpl = fixed              ; Jitterbuffer implementation, used on the receiving side of an OSS
                                  ; channel. Two implementations are currenlty available - "fixed"
                                  ; (with size always equals to jbmax-size) and "adaptive" (with
                                  ; variable size, actually the new jb of IAX2). Defaults to fixed.

    ; jblog = no                  ; Enables jitterbuffer frame logging. Defaults to "no".
    ;-----------------------------------------------------------------------------------

[card1]
    ; device = /dev/dsp1   ; alternate device

END_CONFIG

.. and so on for the other cards.

 */

/*
 * The following parameters are used in the driver:
 *
 *  FRAME_SIZE the size of an audio frame, in samples.
 *    160 is used almost universally, so you should not change it.
 *
 *  FRAGS   the argument for the SETFRAGMENT ioctl.
 *    Overridden by the 'frags' parameter in oss.conf
 *
 *    Bits 0-7 are the base-2 log of the device's block size,
 *    bits 16-31 are the number of blocks in the driver's queue.
 *    There are a lot of differences in the way this parameter
 *    is supported by different drivers, so you may need to
 *    experiment a bit with the value.
 *    A good default for linux is 30 blocks of 64 bytes, which
 *    results in 6 frames of 320 bytes (160 samples).
 *    FreeBSD works decently with blocks of 256 or 512 bytes,
 *    leaving the number unspecified.
 *    Note that this only refers to the device buffer size,
 *    this module will then try to keep the lenght of audio
 *    buffered within small constraints.
 *
 *  QUEUE_SIZE The max number of blocks actually allowed in the device
 *    driver's buffer, irrespective of the available number.
 *    Overridden by the 'queuesize' parameter in oss.conf
 *
 *    Should be >=2, and at most as large as the hw queue above
 *    (otherwise it will never be full).
 */

#define FRAME_SIZE   160
#define  QUEUE_SIZE  10

#if defined(__FreeBSD__)
#define  FRAGS 0x8
#else
#define  FRAGS ( ( (6 * 5) << 16 ) | 0x6 )
#endif

/*
 * XXX text message sizes are probably 256 chars, but i am
 * not sure if there is a suitable definition anywhere.
 */
#define TEXT_SIZE 256

#if 0
#define  TRYOPEN  1           /* try to open on startup */
#endif
#define  O_CLOSE  0x444       /* special 'close' mode for device */
/* Which device to use */
#if defined( __OpenBSD__ ) || defined( __NetBSD__ )
#define DEV_DSP "/dev/audio"
#else
#define DEV_DSP "/dev/dsp"
#endif

static char *config = "oss.conf";   /* default config file */

static int oss_debug;

/*!
 * \brief descriptor for one of our channels.
 *
 * There is one used for 'default' values (from the [general] entry in
 * the configuration file), and then one instance for each device
 * (the default is cloned from [general], others are only created
 * if the relevant section exists).
 */
struct chan_oss_pvt {
   struct chan_oss_pvt *next;

   char *name;
   int total_blocks;       /*!< total blocks in the output device */
   int sounddev;
   enum { M_UNSET, M_FULL, M_READ, M_WRITE } duplex;
   int autoanswer;             /*!< Boolean: whether to answer the immediately upon calling */
   int autohangup;             /*!< Boolean: whether to hangup the call when the remote end hangs up */
   int hookstate;              /*!< Boolean: 1 if offhook; 0 if onhook */
   char *mixer_cmd;        /*!< initial command to issue to the mixer */
   unsigned int queuesize;    /*!< max fragments in queue */
   unsigned int frags;        /*!< parameter for SETFRAGMENT */

   int warned;             /*!< various flags used for warnings */
#define WARN_used_blocks   1
#define WARN_speed      2
#define WARN_frag    4
   int w_errors;           /*!< overfull in the write path */
   struct timeval lastopen;

   int overridecontext;
   int mute;

   /*! boost support. BOOST_SCALE * 10 ^(BOOST_MAX/20) must
    *  be representable in 16 bits to avoid overflows.
    */
#define  BOOST_SCALE (1<<9)
#define  BOOST_MAX   40       /*!< slightly less than 7 bits */
   int boost;              /*!< input boost, scaled by BOOST_SCALE */
   char device[64];        /*!< device to open */

   pthread_t sthread;

   struct ast_channel *owner;

   struct video_desc *env;       /*!< parameters for video support */

   char ext[AST_MAX_EXTENSION];
   char ctx[AST_MAX_CONTEXT];
   char language[MAX_LANGUAGE];
   char cid_name[256];         /*!< Initial CallerID name */
   char cid_num[256];          /*!< Initial CallerID number  */
   char mohinterpret[MAX_MUSICCLASS];

   /*! buffers used in oss_write */
   char oss_write_buf[FRAME_SIZE * 2];
   int oss_write_dst;
   /*! buffers used in oss_read - AST_FRIENDLY_OFFSET space for headers
    *  plus enough room for a full frame
    */
   char oss_read_buf[FRAME_SIZE * 2 + AST_FRIENDLY_OFFSET];
   int readpos;            /*!< read position above */
   struct ast_frame read_f;   /*!< returned by oss_read */
};

/*! forward declaration */
static struct chan_oss_pvt *find_desc(char *dev);

static char *oss_active;    /*!< the active device */

/*! \brief return the pointer to the video descriptor */
struct video_desc *get_video_desc(struct ast_channel *c)
{
   struct chan_oss_pvt *o = c ? c->tech_pvt : find_desc(oss_active);
   return o ? o->env : NULL;
}
static struct chan_oss_pvt oss_default = {
   .sounddev = -1,
   .duplex = M_UNSET,         /* XXX check this */
   .autoanswer = 1,
   .autohangup = 1,
   .queuesize = QUEUE_SIZE,
   .frags = FRAGS,
   .ext = "s",
   .ctx = "default",
   .readpos = AST_FRIENDLY_OFFSET,  /* start here on reads */
   .lastopen = { 0, 0 },
   .boost = BOOST_SCALE,
};


static int setformat(struct chan_oss_pvt *o, int mode);

static struct ast_channel *oss_request(const char *type, int format, void *data, int *cause);
static int oss_digit_begin(struct ast_channel *c, char digit);
static int oss_digit_end(struct ast_channel *c, char digit, unsigned int duration);
static int oss_text(struct ast_channel *c, const char *text);
static int oss_hangup(struct ast_channel *c);
static int oss_answer(struct ast_channel *c);
static struct ast_frame *oss_read(struct ast_channel *chan);
static int oss_call(struct ast_channel *c, char *dest, int timeout);
static int oss_write(struct ast_channel *chan, struct ast_frame *f);
static int oss_indicate(struct ast_channel *chan, int cond, const void *data, size_t datalen);
static int oss_fixup(struct ast_channel *oldchan, struct ast_channel *newchan);
static char tdesc[] = "OSS Console Channel Driver";

/* cannot do const because need to update some fields at runtime */
static struct ast_channel_tech oss_tech = {
   .type = "Console",
   .description = tdesc,
   .capabilities = AST_FORMAT_SLINEAR, /* overwritten later */
   .requester = oss_request,
   .send_digit_begin = oss_digit_begin,
   .send_digit_end = oss_digit_end,
   .send_text = oss_text,
   .hangup = oss_hangup,
   .answer = oss_answer,
   .read = oss_read,
   .call = oss_call,
   .write = oss_write,
   .write_video = console_write_video,
   .indicate = oss_indicate,
   .fixup = oss_fixup,
};

/*!
 * \brief returns a pointer to the descriptor with the given name
 */
static struct chan_oss_pvt *find_desc(char *dev)
{
   struct chan_oss_pvt *o = NULL;

   if (!dev)
      ast_log(LOG_WARNING, "null dev\n");

   for (o = oss_default.next; o && o->name && dev && strcmp(o->name, dev) != 0; o = o->next);

   if (!o)
      ast_log(LOG_WARNING, "could not find <%s>\n", dev ? dev : "--no-device--");

   return o;
}

/* !
 * \brief split a string in extension-context, returns pointers to malloc'ed
 *        strings.
 *
 * If we do not have 'overridecontext' then the last @ is considered as
 * a context separator, and the context is overridden.
 * This is usually not very necessary as you can play with the dialplan,
 * and it is nice not to need it because you have '@' in SIP addresses.
 *
 * \return the buffer address.
 */
static char *ast_ext_ctx(const char *src, char **ext, char **ctx)
{
   struct chan_oss_pvt *o = find_desc(oss_active);

   if (ext == NULL || ctx == NULL)
      return NULL;         /* error */

   *ext = *ctx = NULL;

   if (src && *src != '\0')
      *ext = ast_strdup(src);

   if (*ext == NULL)
      return NULL;

   if (!o->overridecontext) {
      /* parse from the right */
      *ctx = strrchr(*ext, '@');
      if (*ctx)
         *(*ctx)++ = '\0';
   }

   return *ext;
}

/*!
 * \brief Returns the number of blocks used in the audio output channel
 */
static int used_blocks(struct chan_oss_pvt *o)
{
   struct audio_buf_info info;

   if (ioctl(o->sounddev, SNDCTL_DSP_GETOSPACE, &info)) {
      if (!(o->warned & WARN_used_blocks)) {
         ast_log(LOG_WARNING, "Error reading output space\n");
         o->warned |= WARN_used_blocks;
      }
      return 1;
   }

   if (o->total_blocks == 0) {
      if (0)               /* debugging */
         ast_log(LOG_WARNING, "fragtotal %d size %d avail %d\n", info.fragstotal, info.fragsize, info.fragments);
      o->total_blocks = info.fragments;
   }

   return o->total_blocks - info.fragments;
}

/*! Write an exactly FRAME_SIZE sized frame */
static int soundcard_writeframe(struct chan_oss_pvt *o, short *data)
{
   int res;

   if (o->sounddev < 0)
      setformat(o, O_RDWR);
   if (o->sounddev < 0)
      return 0;            /* not fatal */
   /*
    * Nothing complex to manage the audio device queue.
    * If the buffer is full just drop the extra, otherwise write.
    * XXX in some cases it might be useful to write anyways after
    * a number of failures, to restart the output chain.
    */
   res = used_blocks(o);
   if (res > o->queuesize) {  /* no room to write a block */
      if (o->w_errors++ == 0 && (oss_debug & 0x4))
         ast_log(LOG_WARNING, "write: used %d blocks (%d)\n", res, o->w_errors);
      return 0;
   }
   o->w_errors = 0;
   return write(o->sounddev, (void *)data, FRAME_SIZE * 2);
}

/*!
 * reset and close the device if opened,
 * then open and initialize it in the desired mode,
 * trigger reads and writes so we can start using it.
 */
static int setformat(struct chan_oss_pvt *o, int mode)
{
   int fmt, desired, res, fd;

   if (o->sounddev >= 0) {
      ioctl(o->sounddev, SNDCTL_DSP_RESET, 0);
      close(o->sounddev);
      o->duplex = M_UNSET;
      o->sounddev = -1;
   }
   if (mode == O_CLOSE)    /* we are done */
      return 0;
   if (ast_tvdiff_ms(ast_tvnow(), o->lastopen) < 1000)
      return -1;           /* don't open too often */
   o->lastopen = ast_tvnow();
   fd = o->sounddev = open(o->device, mode | O_NONBLOCK);
   if (fd < 0) {
      ast_log(LOG_WARNING, "Unable to re-open DSP device %s: %s\n", o->device, strerror(errno));
      return -1;
   }
   if (o->owner)
      ast_channel_set_fd(o->owner, 0, fd);

#if __BYTE_ORDER == __LITTLE_ENDIAN
   fmt = AFMT_S16_LE;
#else
   fmt = AFMT_S16_BE;
#endif
   res = ioctl(fd, SNDCTL_DSP_SETFMT, &fmt);
   if (res < 0) {
      ast_log(LOG_WARNING, "Unable to set format to 16-bit signed\n");
      return -1;
   }
   switch (mode) {
   case O_RDWR:
      res = ioctl(fd, SNDCTL_DSP_SETDUPLEX, 0);
      /* Check to see if duplex set (FreeBSD Bug) */
      res = ioctl(fd, SNDCTL_DSP_GETCAPS, &fmt);
      if (res == 0 && (fmt & DSP_CAP_DUPLEX)) {
         ast_verb(2, "Console is full duplex\n");
         o->duplex = M_FULL;
      };
      break;

   case O_WRONLY:
      o->duplex = M_WRITE;
      break;

   case O_RDONLY:
      o->duplex = M_READ;
      break;
   }

   fmt = 0;
   res = ioctl(fd, SNDCTL_DSP_STEREO, &fmt);
   if (res < 0) {
      ast_log(LOG_WARNING, "Failed to set audio device to mono\n");
      return -1;
   }
   fmt = desired = DEFAULT_SAMPLE_RATE;   /* 8000 Hz desired */
   res = ioctl(fd, SNDCTL_DSP_SPEED, &fmt);

   if (res < 0) {
      ast_log(LOG_WARNING, "Failed to set audio device to mono\n");
      return -1;
   }
   if (fmt != desired) {
      if (!(o->warned & WARN_speed)) {
         ast_log(LOG_WARNING,
             "Requested %d Hz, got %d Hz -- sound may be choppy\n",
             desired, fmt);
         o->warned |= WARN_speed;
      }
   }
   /*
    * on Freebsd, SETFRAGMENT does not work very well on some cards.
    * Default to use 256 bytes, let the user override
    */
   if (o->frags) {
      fmt = o->frags;
      res = ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &fmt);
      if (res < 0) {
         if (!(o->warned & WARN_frag)) {
            ast_log(LOG_WARNING,
               "Unable to set fragment size -- sound may be choppy\n");
            o->warned |= WARN_frag;
         }
      }
   }
   /* on some cards, we need SNDCTL_DSP_SETTRIGGER to start outputting */
   res = PCM_ENABLE_INPUT | PCM_ENABLE_OUTPUT;
   res = ioctl(fd, SNDCTL_DSP_SETTRIGGER, &res);
   /* it may fail if we are in half duplex, never mind */
   return 0;
}

/*
 * some of the standard methods supported by channels.
 */
static int oss_digit_begin(struct ast_channel *c, char digit)
{
   return 0;
}

static int oss_digit_end(struct ast_channel *c, char digit, unsigned int duration)
{
   /* no better use for received digits than print them */
   ast_verbose(" << Console Received digit %c of duration %u ms >> \n", 
      digit, duration);
   return 0;
}

static int oss_text(struct ast_channel *c, const char *text)
{
   /* print received messages */
   ast_verbose(" << Console Received text %s >> \n", text);
   return 0;
}

/*!
 * \brief handler for incoming calls. Either autoanswer, or start ringing
 */
static int oss_call(struct ast_channel *c, char *dest, int timeout)
{
   struct chan_oss_pvt *o = c->tech_pvt;
   struct ast_frame f = { 0, };
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(name);
      AST_APP_ARG(flags);
   );
   char *parse = ast_strdupa(dest);

   AST_NONSTANDARD_APP_ARGS(args, parse, '/');

   ast_verbose(" << Call to device '%s' dnid '%s' rdnis '%s' on console from '%s' <%s> >>\n", dest, c->cid.cid_dnid, c->cid.cid_rdnis, c->cid.cid_name, c->cid.cid_num);
   if (!ast_strlen_zero(args.flags) && strcasecmp(args.flags, "answer") == 0) {
      f.frametype = AST_FRAME_CONTROL;
      f.subclass = AST_CONTROL_ANSWER;
      ast_queue_frame(c, &f);
   } else if (!ast_strlen_zero(args.flags) && strcasecmp(args.flags, "noanswer") == 0) {
      f.frametype = AST_FRAME_CONTROL;
      f.subclass = AST_CONTROL_RINGING;
      ast_queue_frame(c, &f);
      ast_indicate(c, AST_CONTROL_RINGING);
   } else if (o->autoanswer) {
      ast_verbose(" << Auto-answered >> \n");
      f.frametype = AST_FRAME_CONTROL;
      f.subclass = AST_CONTROL_ANSWER;
      ast_queue_frame(c, &f);
      o->hookstate = 1;
   } else {
      ast_verbose("<< Type 'answer' to answer, or use 'autoanswer' for future calls >> \n");
      f.frametype = AST_FRAME_CONTROL;
      f.subclass = AST_CONTROL_RINGING;
      ast_queue_frame(c, &f);
      ast_indicate(c, AST_CONTROL_RINGING);
   }
   return 0;
}

/*!
 * \brief remote side answered the phone
 */
static int oss_answer(struct ast_channel *c)
{
   struct chan_oss_pvt *o = c->tech_pvt;
   ast_verbose(" << Console call has been answered >> \n");
   ast_setstate(c, AST_STATE_UP);
   o->hookstate = 1;
   return 0;
}

static int oss_hangup(struct ast_channel *c)
{
   struct chan_oss_pvt *o = c->tech_pvt;

   c->tech_pvt = NULL;
   o->owner = NULL;
   ast_verbose(" << Hangup on console >> \n");
   console_video_uninit(o->env);
   ast_module_unref(ast_module_info->self);
   if (o->hookstate) {
      if (o->autoanswer || o->autohangup) {
         /* Assume auto-hangup too */
         o->hookstate = 0;
         setformat(o, O_CLOSE);
      }
   }
   return 0;
}

/*! \brief used for data coming from the network */
static int oss_write(struct ast_channel *c, struct ast_frame *f)
{
   int src;
   struct chan_oss_pvt *o = c->tech_pvt;

   /*
    * we could receive a block which is not a multiple of our
    * FRAME_SIZE, so buffer it locally and write to the device
    * in FRAME_SIZE chunks.
    * Keep the residue stored for future use.
    */
   src = 0;             /* read position into f->data */
   while (src < f->datalen) {
      /* Compute spare room in the buffer */
      int l = sizeof(o->oss_write_buf) - o->oss_write_dst;

      if (f->datalen - src >= l) {  /* enough to fill a frame */
         memcpy(o->oss_write_buf + o->oss_write_dst, f->data.ptr + src, l);
         soundcard_writeframe(o, (short *) o->oss_write_buf);
         src += l;
         o->oss_write_dst = 0;
      } else {          /* copy residue */
         l = f->datalen - src;
         memcpy(o->oss_write_buf + o->oss_write_dst, f->data.ptr + src, l);
         src += l;         /* but really, we are done */
         o->oss_write_dst += l;
      }
   }
   return 0;
}

static struct ast_frame *oss_read(struct ast_channel *c)
{
   int res;
   struct chan_oss_pvt *o = c->tech_pvt;
   struct ast_frame *f = &o->read_f;

   /* XXX can be simplified returning &ast_null_frame */
   /* prepare a NULL frame in case we don't have enough data to return */
   memset(f, '\0', sizeof(struct ast_frame));
   f->frametype = AST_FRAME_NULL;
   f->src = oss_tech.type;

   res = read(o->sounddev, o->oss_read_buf + o->readpos, sizeof(o->oss_read_buf) - o->readpos);
   if (res < 0)            /* audio data not ready, return a NULL frame */
      return f;

   o->readpos += res;
   if (o->readpos < sizeof(o->oss_read_buf)) /* not enough samples */
      return f;

   if (o->mute)
      return f;

   o->readpos = AST_FRIENDLY_OFFSET;   /* reset read pointer for next frame */
   if (c->_state != AST_STATE_UP)   /* drop data if frame is not up */
      return f;
   /* ok we can build and deliver the frame to the caller */
   f->frametype = AST_FRAME_VOICE;
   f->subclass = AST_FORMAT_SLINEAR;
   f->samples = FRAME_SIZE;
   f->datalen = FRAME_SIZE * 2;
   f->data.ptr = o->oss_read_buf + AST_FRIENDLY_OFFSET;
   if (o->boost != BOOST_SCALE) {   /* scale and clip values */
      int i, x;
      int16_t *p = (int16_t *) f->data.ptr;
      for (i = 0; i < f->samples; i++) {
         x = (p[i] * o->boost) / BOOST_SCALE;
         if (x > 32767)
            x = 32767;
         else if (x < -32768)
            x = -32768;
         p[i] = x;
      }
   }

   f->offset = AST_FRIENDLY_OFFSET;
   return f;
}

static int oss_fixup(struct ast_channel *oldchan, struct ast_channel *newchan)
{
   struct chan_oss_pvt *o = newchan->tech_pvt;
   o->owner = newchan;
   return 0;
}

static int oss_indicate(struct ast_channel *c, int cond, const void *data, size_t datalen)
{
   struct chan_oss_pvt *o = c->tech_pvt;
   int res = 0;

   switch (cond) {
   case AST_CONTROL_BUSY:
   case AST_CONTROL_CONGESTION:
   case AST_CONTROL_RINGING:
   case -1:
      res = -1;
      break;
   case AST_CONTROL_PROGRESS:
   case AST_CONTROL_PROCEEDING:
   case AST_CONTROL_VIDUPDATE:
   case AST_CONTROL_SRCUPDATE:
      break;
   case AST_CONTROL_HOLD:
      ast_verbose(" << Console Has Been Placed on Hold >> \n");
      ast_moh_start(c, data, o->mohinterpret);
      break;
   case AST_CONTROL_UNHOLD:
      ast_verbose(" << Console Has Been Retrieved from Hold >> \n");
      ast_moh_stop(c);
      break;
   default:
      ast_log(LOG_WARNING, "Don't know how to display condition %d on %s\n", cond, c->name);
      return -1;
   }

   return res;
}

/*!
 * \brief allocate a new channel.
 */
static struct ast_channel *oss_new(struct chan_oss_pvt *o, char *ext, char *ctx, int state)
{
   struct ast_channel *c;

   c = ast_channel_alloc(1, state, o->cid_num, o->cid_name, "", ext, ctx, 0, "Console/%s", o->device + 5);
   if (c == NULL)
      return NULL;
   c->tech = &oss_tech;
   if (o->sounddev < 0)
      setformat(o, O_RDWR);
   ast_channel_set_fd(c, 0, o->sounddev); /* -1 if device closed, override later */
   c->nativeformats = AST_FORMAT_SLINEAR;
   /* if the console makes the call, add video to the offer */
   if (state == AST_STATE_RINGING)
      c->nativeformats |= console_video_formats;

   c->readformat = AST_FORMAT_SLINEAR;
   c->writeformat = AST_FORMAT_SLINEAR;
   c->tech_pvt = o;

   if (!ast_strlen_zero(o->language))
      ast_string_field_set(c, language, o->language);
   /* Don't use ast_set_callerid() here because it will
    * generate a needless NewCallerID event */
   c->cid.cid_ani = ast_strdup(o->cid_num);
   if (!ast_strlen_zero(ext))
      c->cid.cid_dnid = ast_strdup(ext);

   o->owner = c;
   ast_module_ref(ast_module_info->self);
   ast_jb_configure(c, &global_jbconf);
   if (state != AST_STATE_DOWN) {
      if (ast_pbx_start(c)) {
         ast_log(LOG_WARNING, "Unable to start PBX on %s\n", c->name);
         ast_hangup(c);
         o->owner = c = NULL;
      }
   }
   console_video_start(get_video_desc(c), c); /* XXX cleanup */

   return c;
}

static struct ast_channel *oss_request(const char *type, int format, void *data, int *cause)
{
   struct ast_channel *c;
   struct chan_oss_pvt *o;
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(name);
      AST_APP_ARG(flags);
   );
   char *parse = ast_strdupa(data);

   AST_NONSTANDARD_APP_ARGS(args, parse, '/');
   o = find_desc(args.name);

   ast_log(LOG_WARNING, "oss_request ty <%s> data 0x%p <%s>\n", type, data, (char *) data);
   if (o == NULL) {
      ast_log(LOG_NOTICE, "Device %s not found\n", args.name);
      /* XXX we could default to 'dsp' perhaps ? */
      return NULL;
   }
   if ((format & AST_FORMAT_SLINEAR) == 0) {
      ast_log(LOG_NOTICE, "Format 0x%x unsupported\n", format);
      return NULL;
   }
   if (o->owner) {
      ast_log(LOG_NOTICE, "Already have a call (chan %p) on the OSS channel\n", o->owner);
      *cause = AST_CAUSE_BUSY;
      return NULL;
   }
   c = oss_new(o, NULL, NULL, AST_STATE_DOWN);
   if (c == NULL) {
      ast_log(LOG_WARNING, "Unable to create new OSS channel\n");
      return NULL;
   }
   return c;
}

static void store_config_core(struct chan_oss_pvt *o, const char *var, const char *value);

/*! Generic console command handler. Basically a wrapper for a subset
 *  of config file options which are also available from the CLI
 */
static char *console_cmd(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct chan_oss_pvt *o = find_desc(oss_active);
   const char *var, *value;
   switch (cmd) {
   case CLI_INIT:
      e->command = CONSOLE_VIDEO_CMDS;
      e->usage = 
         "Usage: " CONSOLE_VIDEO_CMDS "...\n"
         "       Generic handler for console commands.\n";
      return NULL;

   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc < e->args)
      return CLI_SHOWUSAGE;
   if (o == NULL) {
      ast_log(LOG_WARNING, "Cannot find device %s (should not happen!)\n",
         oss_active);
      return CLI_FAILURE;
   }
   var = a->argv[e->args-1];
   value = a->argc > e->args ? a->argv[e->args] : NULL;
   if (value)      /* handle setting */
      store_config_core(o, var, value);
   if (!console_video_cli(o->env, var, a->fd))  /* print video-related values */
      return CLI_SUCCESS;
   /* handle other values */
   if (!strcasecmp(var, "device")) {
      ast_cli(a->fd, "device is [%s]\n", o->device);
   }
   return CLI_SUCCESS;
}

static char *console_autoanswer(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct chan_oss_pvt *o = find_desc(oss_active);

   switch (cmd) {
   case CLI_INIT:
      e->command = "console autoanswer [on|off]";
      e->usage =
         "Usage: console autoanswer [on|off]\n"
         "       Enables or disables autoanswer feature.  If used without\n"
         "       argument, displays the current on/off status of autoanswer.\n"
         "       The default value of autoanswer is in 'oss.conf'.\n";
      return NULL;

   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc == e->args - 1) {
      ast_cli(a->fd, "Auto answer is %s.\n", o->autoanswer ? "on" : "off");
      return CLI_SUCCESS;
   }
   if (a->argc != e->args)
      return CLI_SHOWUSAGE;
   if (o == NULL) {
      ast_log(LOG_WARNING, "Cannot find device %s (should not happen!)\n",
          oss_active);
      return CLI_FAILURE;
   }
   if (!strcasecmp(a->argv[e->args-1], "on"))
      o->autoanswer = 1;
   else if (!strcasecmp(a->argv[e->args - 1], "off"))
      o->autoanswer = 0;
   else
      return CLI_SHOWUSAGE;
   return CLI_SUCCESS;
}

/*! \brief helper function for the answer key/cli command */
static char *console_do_answer(int fd)
{
   struct ast_frame f = { AST_FRAME_CONTROL, AST_CONTROL_ANSWER };
   struct chan_oss_pvt *o = find_desc(oss_active);
   if (!o->owner) {
      if (fd > -1)
         ast_cli(fd, "No one is calling us\n");
      return CLI_FAILURE;
   }
   o->hookstate = 1;
   ast_queue_frame(o->owner, &f);
   return CLI_SUCCESS;
}

/*!
 * \brief answer command from the console
 */
static char *console_answer(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   switch (cmd) {
   case CLI_INIT:
      e->command = "console answer";
      e->usage =
         "Usage: console answer\n"
         "       Answers an incoming call on the console (OSS) channel.\n";
      return NULL;

   case CLI_GENERATE:
      return NULL;   /* no completion */
   }
   if (a->argc != e->args)
      return CLI_SHOWUSAGE;
   return console_do_answer(a->fd);
}

/*!
 * \brief Console send text CLI command
 *
 * \note concatenate all arguments into a single string. argv is NULL-terminated
 * so we can use it right away
 */
static char *console_sendtext(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct chan_oss_pvt *o = find_desc(oss_active);
   char buf[TEXT_SIZE];

   if (cmd == CLI_INIT) {
      e->command = "console send text";
      e->usage =
         "Usage: console send text <message>\n"
         "       Sends a text message for display on the remote terminal.\n";
      return NULL;
   } else if (cmd == CLI_GENERATE)
      return NULL;

   if (a->argc < e->args + 1)
      return CLI_SHOWUSAGE;
   if (!o->owner) {
      ast_cli(a->fd, "Not in a call\n");
      return CLI_FAILURE;
   }
   ast_join(buf, sizeof(buf) - 1, a->argv + e->args);
   if (!ast_strlen_zero(buf)) {
      struct ast_frame f = { 0, };
      int i = strlen(buf);
      buf[i] = '\n';
      f.frametype = AST_FRAME_TEXT;
      f.subclass = 0;
      f.data.ptr = buf;
      f.datalen = i + 1;
      ast_queue_frame(o->owner, &f);
   }
   return CLI_SUCCESS;
}

static char *console_hangup(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct chan_oss_pvt *o = find_desc(oss_active);

   if (cmd == CLI_INIT) {
      e->command = "console hangup";
      e->usage =
         "Usage: console hangup\n"
         "       Hangs up any call currently placed on the console.\n";
      return NULL;
   } else if (cmd == CLI_GENERATE)
      return NULL;

   if (a->argc != e->args)
      return CLI_SHOWUSAGE;
   if (!o->owner && !o->hookstate) { /* XXX maybe only one ? */
      ast_cli(a->fd, "No call to hang up\n");
      return CLI_FAILURE;
   }
   o->hookstate = 0;
   if (o->owner)
      ast_queue_hangup_with_cause(o->owner, AST_CAUSE_NORMAL_CLEARING);
   setformat(o, O_CLOSE);
   return CLI_SUCCESS;
}

static char *console_flash(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct ast_frame f = { AST_FRAME_CONTROL, AST_CONTROL_FLASH };
   struct chan_oss_pvt *o = find_desc(oss_active);

   if (cmd == CLI_INIT) {
      e->command = "console flash";
      e->usage =
         "Usage: console flash\n"
         "       Flashes the call currently placed on the console.\n";
      return NULL;
   } else if (cmd == CLI_GENERATE)
      return NULL;

   if (a->argc != e->args)
      return CLI_SHOWUSAGE;
   if (!o->owner) {        /* XXX maybe !o->hookstate too ? */
      ast_cli(a->fd, "No call to flash\n");
      return CLI_FAILURE;
   }
   o->hookstate = 0;
   if (o->owner)
      ast_queue_frame(o->owner, &f);
   return CLI_SUCCESS;
}

static char *console_dial(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   char *s = NULL, *mye = NULL, *myc = NULL;
   struct chan_oss_pvt *o = find_desc(oss_active);

   if (cmd == CLI_INIT) {
      e->command = "console dial";
      e->usage =
         "Usage: console dial [extension[@context]]\n"
         "       Dials a given extension (and context if specified)\n";
      return NULL;
   } else if (cmd == CLI_GENERATE)
      return NULL;

   if (a->argc > e->args + 1)
      return CLI_SHOWUSAGE;
   if (o->owner) {   /* already in a call */
      int i;
      struct ast_frame f = { AST_FRAME_DTMF, 0 };

      if (a->argc == e->args) {  /* argument is mandatory here */
         ast_cli(a->fd, "Already in a call. You can only dial digits until you hangup.\n");
         return CLI_FAILURE;
      }
      s = a->argv[e->args];
      /* send the string one char at a time */
      for (i = 0; i < strlen(s); i++) {
         f.subclass = s[i];
         ast_queue_frame(o->owner, &f);
      }
      return CLI_SUCCESS;
   }
   /* if we have an argument split it into extension and context */
   if (a->argc == e->args + 1)
      s = ast_ext_ctx(a->argv[e->args], &mye, &myc);
   /* supply default values if needed */
   if (mye == NULL)
      mye = o->ext;
   if (myc == NULL)
      myc = o->ctx;
   if (ast_exists_extension(NULL, myc, mye, 1, NULL)) {
      o->hookstate = 1;
      oss_new(o, mye, myc, AST_STATE_RINGING);
   } else
      ast_cli(a->fd, "No such extension '%s' in context '%s'\n", mye, myc);
   if (s)
      ast_free(s);
   return CLI_SUCCESS;
}

static char *console_mute(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct chan_oss_pvt *o = find_desc(oss_active);
   char *s;
   int toggle = 0;
   
   if (cmd == CLI_INIT) {
      e->command = "console {mute|unmute} [toggle]";
      e->usage =
         "Usage: console {mute|unmute} [toggle]\n"
         "       Mute/unmute the microphone.\n";
      return NULL;
   } else if (cmd == CLI_GENERATE)
      return NULL;

   if (a->argc > e->args)
      return CLI_SHOWUSAGE;
   if (a->argc == e->args) {
      if (strcasecmp(a->argv[e->args-1], "toggle"))
         return CLI_SHOWUSAGE;
      toggle = 1;
   }
   s = a->argv[e->args-2];
   if (!strcasecmp(s, "mute"))
      o->mute = toggle ? !o->mute : 1;
   else if (!strcasecmp(s, "unmute"))
      o->mute = toggle ? !o->mute : 0;
   else
      return CLI_SHOWUSAGE;
   ast_cli(a->fd, "Console mic is %s\n", o->mute ? "off" : "on");
   return CLI_SUCCESS;
}

static char *console_transfer(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct chan_oss_pvt *o = find_desc(oss_active);
   struct ast_channel *b = NULL;
   char *tmp, *ext, *ctx;

   switch (cmd) {
   case CLI_INIT:
      e->command = "console transfer";
      e->usage =
         "Usage: console transfer <extension>[@context]\n"
         "       Transfers the currently connected call to the given extension (and\n"
         "       context if specified)\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc != 3)
      return CLI_SHOWUSAGE;
   if (o == NULL)
      return CLI_FAILURE;
   if (o->owner == NULL || (b = ast_bridged_channel(o->owner)) == NULL) {
      ast_cli(a->fd, "There is no call to transfer\n");
      return CLI_SUCCESS;
   }

   tmp = ast_ext_ctx(a->argv[2], &ext, &ctx);
   if (ctx == NULL)        /* supply default context if needed */
      ctx = o->owner->context;
   if (!ast_exists_extension(b, ctx, ext, 1, b->cid.cid_num))
      ast_cli(a->fd, "No such extension exists\n");
   else {
      ast_cli(a->fd, "Whee, transferring %s to %s@%s.\n", b->name, ext, ctx);
      if (ast_async_goto(b, ctx, ext, 1))
         ast_cli(a->fd, "Failed to transfer :(\n");
   }
   if (tmp)
      ast_free(tmp);
   return CLI_SUCCESS;
}

static char *console_active(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   switch (cmd) {
   case CLI_INIT:
      e->command = "console active";
      e->usage =
         "Usage: console active [device]\n"
         "       If used without a parameter, displays which device is the current\n"
         "       console.  If a device is specified, the console sound device is changed to\n"
         "       the device specified.\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc == 2)
      ast_cli(a->fd, "active console is [%s]\n", oss_active);
   else if (a->argc != 3)
      return CLI_SHOWUSAGE;
   else {
      struct chan_oss_pvt *o;
      if (strcmp(a->argv[2], "show") == 0) {
         for (o = oss_default.next; o; o = o->next)
            ast_cli(a->fd, "device [%s] exists\n", o->name);
         return CLI_SUCCESS;
      }
      o = find_desc(a->argv[2]);
      if (o == NULL)
         ast_cli(a->fd, "No device [%s] exists\n", a->argv[2]);
      else
         oss_active = o->name;
   }
   return CLI_SUCCESS;
}

/*!
 * \brief store the boost factor
 */
static void store_boost(struct chan_oss_pvt *o, const char *s)
{
   double boost = 0;
   if (sscanf(s, "%30lf", &boost) != 1) {
      ast_log(LOG_WARNING, "invalid boost <%s>\n", s);
      return;
   }
   if (boost < -BOOST_MAX) {
      ast_log(LOG_WARNING, "boost %s too small, using %d\n", s, -BOOST_MAX);
      boost = -BOOST_MAX;
   } else if (boost > BOOST_MAX) {
      ast_log(LOG_WARNING, "boost %s too large, using %d\n", s, BOOST_MAX);
      boost = BOOST_MAX;
   }
   boost = exp(log(10) * boost / 20) * BOOST_SCALE;
   o->boost = boost;
   ast_log(LOG_WARNING, "setting boost %s to %d\n", s, o->boost);
}

static char *console_boost(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct chan_oss_pvt *o = find_desc(oss_active);

   switch (cmd) {
   case CLI_INIT:
      e->command = "console boost";
      e->usage =
         "Usage: console boost [boost in dB]\n"
         "       Sets or display mic boost in dB\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc == 2)
      ast_cli(a->fd, "boost currently %5.1f\n", 20 * log10(((double) o->boost / (double) BOOST_SCALE)));
   else if (a->argc == 3)
      store_boost(o, a->argv[2]);
   return CLI_SUCCESS;
}

static struct ast_cli_entry cli_oss[] = {
   AST_CLI_DEFINE(console_answer, "Answer an incoming console call"),
   AST_CLI_DEFINE(console_hangup, "Hangup a call on the console"),
   AST_CLI_DEFINE(console_flash, "Flash a call on the console"),
   AST_CLI_DEFINE(console_dial, "Dial an extension on the console"),
   AST_CLI_DEFINE(console_mute, "Disable/Enable mic input"),
   AST_CLI_DEFINE(console_transfer, "Transfer a call to a different extension"), 
   AST_CLI_DEFINE(console_cmd, "Generic console command"),
   AST_CLI_DEFINE(console_sendtext, "Send text to the remote device"),
   AST_CLI_DEFINE(console_autoanswer, "Sets/displays autoanswer"),
   AST_CLI_DEFINE(console_boost, "Sets/displays mic boost in dB"),
   AST_CLI_DEFINE(console_active, "Sets/displays active console"),
};

/*!
 * store the mixer argument from the config file, filtering possibly
 * invalid or dangerous values (the string is used as argument for
 * system("mixer %s")
 */
static void store_mixer(struct chan_oss_pvt *o, const char *s)
{
   int i;

   for (i = 0; i < strlen(s); i++) {
      if (!isalnum(s[i]) && strchr(" \t-/", s[i]) == NULL) {
         ast_log(LOG_WARNING, "Suspect char %c in mixer cmd, ignoring:\n\t%s\n", s[i], s);
         return;
      }
   }
   if (o->mixer_cmd)
      ast_free(o->mixer_cmd);
   o->mixer_cmd = ast_strdup(s);
   ast_log(LOG_WARNING, "setting mixer %s\n", s);
}

/*!
 * store the callerid components
 */
static void store_callerid(struct chan_oss_pvt *o, const char *s)
{
   ast_callerid_split(s, o->cid_name, sizeof(o->cid_name), o->cid_num, sizeof(o->cid_num));
}

static void store_config_core(struct chan_oss_pvt *o, const char *var, const char *value)
{
   CV_START(var, value);

   /* handle jb conf */
   if (!ast_jb_read_conf(&global_jbconf, var, value))
      return;

   if (!console_video_config(&o->env, var, value))
      return;  /* matched there */
   CV_BOOL("autoanswer", o->autoanswer);
   CV_BOOL("autohangup", o->autohangup);
   CV_BOOL("overridecontext", o->overridecontext);
   CV_STR("device", o->device);
   CV_UINT("frags", o->frags);
   CV_UINT("debug", oss_debug);
   CV_UINT("queuesize", o->queuesize);
   CV_STR("context", o->ctx);
   CV_STR("language", o->language);
   CV_STR("mohinterpret", o->mohinterpret);
   CV_STR("extension", o->ext);
   CV_F("mixer", store_mixer(o, value));
   CV_F("callerid", store_callerid(o, value))  ;
   CV_F("boost", store_boost(o, value));

   CV_END;
}

/*!
 * grab fields from the config file, init the descriptor and open the device.
 */
static struct chan_oss_pvt *store_config(struct ast_config *cfg, char *ctg)
{
   struct ast_variable *v;
   struct chan_oss_pvt *o;

   if (ctg == NULL) {
      o = &oss_default;
      ctg = "general";
   } else {
      if (!(o = ast_calloc(1, sizeof(*o))))
         return NULL;
      *o = oss_default;
      /* "general" is also the default thing */
      if (strcmp(ctg, "general") == 0) {
         o->name = ast_strdup("dsp");
         oss_active = o->name;
         goto openit;
      }
      o->name = ast_strdup(ctg);
   }

   strcpy(o->mohinterpret, "default");

   o->lastopen = ast_tvnow(); /* don't leave it 0 or tvdiff may wrap */
   /* fill other fields from configuration */
   for (v = ast_variable_browse(cfg, ctg); v; v = v->next) {
      store_config_core(o, v->name, v->value);
   }
   if (ast_strlen_zero(o->device))
      ast_copy_string(o->device, DEV_DSP, sizeof(o->device));
   if (o->mixer_cmd) {
      char *cmd;

      if (asprintf(&cmd, "mixer %s", o->mixer_cmd) < 0) {
         ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
      } else {
         ast_log(LOG_WARNING, "running [%s]\n", cmd);
         if (system(cmd) < 0) {
            ast_log(LOG_WARNING, "system() failed: %s\n", strerror(errno));
         }
         ast_free(cmd);
      }
   }

   /* if the config file requested to start the GUI, do it */
   if (get_gui_startup(o->env))
      console_video_start(o->env, NULL);

   if (o == &oss_default)     /* we are done with the default */
      return NULL;

openit:
#ifdef TRYOPEN
   if (setformat(o, O_RDWR) < 0) {  /* open device */
      ast_verb(1, "Device %s not detected\n", ctg);
      ast_verb(1, "Turn off OSS support by adding " "'noload=chan_oss.so' in /etc/asterisk/modules.conf\n");
      goto error;
   }
   if (o->duplex != M_FULL)
      ast_log(LOG_WARNING, "XXX I don't work right with non " "full-duplex sound cards XXX\n");
#endif /* TRYOPEN */

   /* link into list of devices */
   if (o != &oss_default) {
      o->next = oss_default.next;
      oss_default.next = o;
   }
   return o;

#ifdef TRYOPEN
error:
   if (o != &oss_default)
      ast_free(o);
   return NULL;
#endif
}

static int load_module(void)
{
   struct ast_config *cfg = NULL;
   char *ctg = NULL;
   struct ast_flags config_flags = { 0 };

   /* Copy the default jb config over global_jbconf */
   memcpy(&global_jbconf, &default_jbconf, sizeof(struct ast_jb_conf));

   /* load config file */
   if (!(cfg = ast_config_load(config, config_flags))) {
      ast_log(LOG_NOTICE, "Unable to load config %s\n", config);
      return AST_MODULE_LOAD_DECLINE;
   }

   do {
      store_config(cfg, ctg);
   } while ( (ctg = ast_category_browse(cfg, ctg)) != NULL);

   ast_config_destroy(cfg);

   if (find_desc(oss_active) == NULL) {
      ast_log(LOG_NOTICE, "Device %s not found\n", oss_active);
      /* XXX we could default to 'dsp' perhaps ? */
      /* XXX should cleanup allocated memory etc. */
      return AST_MODULE_LOAD_FAILURE;
   }

   oss_tech.capabilities |= console_video_formats;

   if (ast_channel_register(&oss_tech)) {
      ast_log(LOG_ERROR, "Unable to register channel type 'OSS'\n");
      return AST_MODULE_LOAD_FAILURE;
   }

   ast_cli_register_multiple(cli_oss, sizeof(cli_oss) / sizeof(struct ast_cli_entry));

   return AST_MODULE_LOAD_SUCCESS;
}


static int unload_module(void)
{
   struct chan_oss_pvt *o, *next;

   ast_channel_unregister(&oss_tech);
   ast_cli_unregister_multiple(cli_oss, sizeof(cli_oss) / sizeof(struct ast_cli_entry));

   o = oss_default.next;
   while (o) {
      close(o->sounddev);
      if (o->owner)
         ast_softhangup(o->owner, AST_SOFTHANGUP_APPUNLOAD);
      if (o->owner)
         return -1;
      next = o->next;
      ast_free(o->name);
      ast_free(o);
      o = next;
   }
   return 0;
}

AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "OSS Console Channel Driver");