/**

 * \file pcm/pcm_adpcm.c

 * \ingroup PCM_Plugins

 * \brief PCM Ima-ADPCM Conversion Plugin Interface

 * \author Abramo Bagnara <abramo@alsa-project.org>

 * \author Uros Bizjak <uros@kss-loka.si>

 * \author Jaroslav Kysela <perex@perex.cz>

 * \date 2000-2001

 */

/*

 *  PCM - Ima-ADPCM conversion

 *  Copyright (c) 2000 by Abramo Bagnara <abramo@alsa-project.org>

 *  Copyright (c) 1999 by Uros Bizjak <uros@kss-loka.si>

 *                        Jaroslav Kysela <perex@perex.cz>

 *

 *  Based on Version 1.2, 18-Dec-92 implementation of Intel/DVI ADPCM code

 *  by Jack Jansen, CWI, Amsterdam <Jack.Jansen@cwi.nl>, Copyright 1992

 *  by Stichting Mathematisch Centrum, Amsterdam, The Netherlands.

 *

 *   This library is free software; you can redistribute it and/or modify

 *   it under the terms of the GNU Lesser General Public License as

 *   published by the Free Software Foundation; either version 2.1 of

 *   the License, or (at your option) any later version.

 *

 *   This program is distributed in the hope that it will be useful,

 *   but WITHOUT ANY WARRANTY; without even the implied warranty of

 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *   GNU Lesser General Public License for more details.

 *

 *   You should have received a copy of the GNU Lesser General Public

 *   License along with this library; if not, write to the Free Software

 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 *

 */

/*

These routines convert 16 bit linear PCM samples to 4 bit ADPCM code

and vice versa. The ADPCM code used is the Intel/DVI ADPCM code which

is being recommended by the IMA Digital Audio Technical Working Group.

The algorithm for this coder was taken from:

Proposal for Standardized Audio Interstreamge Formats,

IMA compatibility project proceedings, Vol 2, Issue 2, May 1992.

- No, this is *not* a G.721 coder/decoder. The algorithm used by G.721

  is very complicated, requiring oodles of floating-point ops per

  sample (resulting in very poor performance). I have not done any

  tests myself but various people have assured my that 721 quality is

  actually lower than DVI quality.

- No, it probably isn't a RIFF ADPCM decoder either. Trying to decode

  RIFF ADPCM with these routines seems to result in something

  recognizable but very distorted.

- No, it is not a CDROM-XA coder either, as far as I know. I haven't

  come across a good description of XA yet.

 */

#include "bswap.h"

#include "pcm_local.h"

#include "pcm_plugin.h"

#include "plugin_ops.h"

#ifndef PIC

/* entry for static linking */

const char *_snd_module_pcm_adpcm = "";

#endif

#ifndef DOC_HIDDEN

typedef void (*adpcm_f)(const snd_pcm_channel_area_t *dst_areas,

			snd_pcm_uframes_t dst_offset,

			const snd_pcm_channel_area_t *src_areas,

			snd_pcm_uframes_t src_offset,

			unsigned int channels, snd_pcm_uframes_t frames,

			unsigned int getputidx,

			snd_pcm_adpcm_state_t *states);

typedef struct {

	/* This field need to be the first */

	snd_pcm_plugin_t plug;

	unsigned int getput_idx;

	adpcm_f func;

	snd_pcm_format_t sformat;

	snd_pcm_adpcm_state_t *states;

} snd_pcm_adpcm_t;

#endif

/* First table lookup for Ima-ADPCM quantizer */

static const char IndexAdjust[8] = { -1, -1, -1, -1, 2, 4, 6, 8 };

/* Second table lookup for Ima-ADPCM quantizer */

static const short StepSize[89] = {

	7, 8, 9, 10, 11, 12, 13, 14, 16, 17,

	19, 21, 23, 25, 28, 31, 34, 37, 41, 45,

	50, 55, 60, 66, 73, 80, 88, 97, 107, 118,

	130, 143, 157, 173, 190, 209, 230, 253, 279, 307,

	337, 371, 408, 449, 494, 544, 598, 658, 724, 796,

	876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,

	2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,

	5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,

	15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767

};

static char adpcm_encoder(int sl, snd_pcm_adpcm_state_t * state)

{

	short diff;		/* Difference between sl and predicted sample */

	short pred_diff;	/* Predicted difference to next sample */

	unsigned char sign;	/* sign of diff */

	short step;		/* holds previous StepSize value */

	unsigned char adjust_idx;	/* Index to IndexAdjust lookup table */

	int i;

	/* Compute difference to previous predicted value */

	diff = sl - state->pred_val;

	sign = (diff < 0) ? 0x8 : 0x0;

	if (sign) {

		diff = -diff;

	}

	/*

	 * This code *approximately* computes:

	 *    adjust_idx = diff * 4 / step;

	 *    pred_diff = (adjust_idx + 0.5) * step / 4;

	 *

	 * But in shift step bits are dropped. The net result of this is

	 * that even if you have fast mul/div hardware you cannot put it to

	 * good use since the fix-up would be too expensive.

	 */

	step = StepSize[state->step_idx];

	/* Divide and clamp */

	pred_diff = step >> 3;

	for (adjust_idx = 0, i = 0x4; i; i >>= 1, step >>= 1) {

		if (diff >= step) {

			adjust_idx |= i;

			diff -= step;

			pred_diff += step;

		}

	}

	/* Update and clamp previous predicted value */

	state->pred_val += sign ? -pred_diff : pred_diff;

	if (state->pred_val > 32767) {

		state->pred_val = 32767;

	} else if (state->pred_val < -32768) {

		state->pred_val = -32768;

	}

	/* Update and clamp StepSize lookup table index */

	state->step_idx += IndexAdjust[adjust_idx];

	if (state->step_idx < 0) {

		state->step_idx = 0;

	} else if (state->step_idx > 88) {

		state->step_idx = 88;

	}

	return (sign | adjust_idx);

}

static int adpcm_decoder(unsigned char code, snd_pcm_adpcm_state_t * state)

{

	short pred_diff;	/* Predicted difference to next sample */

	short step;		/* holds previous StepSize value */

	char sign;

	int i;

	/* Separate sign and magnitude */

	sign = code & 0x8;

	code &= 0x7;

	/*

	 * Computes pred_diff = (code + 0.5) * step / 4,

	 * but see comment in adpcm_coder.

	 */

	step = StepSize[state->step_idx];

	/* Compute difference and new predicted value */

	pred_diff = step >> 3;

	for (i = 0x4; i; i >>= 1, step >>= 1) {

		if (code & i) {

			pred_diff += step;

		}

	}

	state->pred_val += (sign) ? -pred_diff : pred_diff;

	/* Clamp output value */

	if (state->pred_val > 32767) {

		state->pred_val = 32767;

	} else if (state->pred_val < -32768) {

		state->pred_val = -32768;

	}

	/* Find new StepSize index value */

	state->step_idx += IndexAdjust[code];

	if (state->step_idx < 0) {

		state->step_idx = 0;

	} else if (state->step_idx > 88) {

		state->step_idx = 88;

	}

	return (state->pred_val);

}

#ifndef DOC_HIDDEN

void snd_pcm_adpcm_decode(const snd_pcm_channel_area_t *dst_areas,

			  snd_pcm_uframes_t dst_offset,

			  const snd_pcm_channel_area_t *src_areas,

			  snd_pcm_uframes_t src_offset,

			  unsigned int channels, snd_pcm_uframes_t frames,

			  unsigned int putidx,

			  snd_pcm_adpcm_state_t *states)

{

#define PUT16_LABELS

#include "plugin_ops.h"

#undef PUT16_LABELS

	void *put = put16_labels[putidx];

	unsigned int channel;

	for (channel = 0; channel < channels; ++channel, ++states) {

		const char *src;

		int srcbit;

		char *dst;

		int src_step, srcbit_step, dst_step;

		snd_pcm_uframes_t frames1;

		const snd_pcm_channel_area_t *src_area = &src_areas[channel];

		const snd_pcm_channel_area_t *dst_area = &dst_areas[channel];

		srcbit = src_area->first + src_area->step * src_offset;

		src = (const char *) src_area->addr + srcbit / 8;

		srcbit %= 8;

		src_step = src_area->step / 8;

		srcbit_step = src_area->step % 8;

		dst = snd_pcm_channel_area_addr(dst_area, dst_offset);

		dst_step = snd_pcm_channel_area_step(dst_area);

		frames1 = frames;

		while (frames1-- > 0) {

			int16_t sample;

			unsigned char v;

			if (srcbit)

				v = *src & 0x0f;

			else

				v = (*src >> 4) & 0x0f;

			sample = adpcm_decoder(v, states);

			goto *put;

#define PUT16_END after

#include "plugin_ops.h"

#undef PUT16_END

		after:

			src += src_step;

			srcbit += srcbit_step;

			if (srcbit == 8) {

				src++;

				srcbit = 0;

			}

			dst += dst_step;

		}

	}

}

void snd_pcm_adpcm_encode(const snd_pcm_channel_area_t *dst_areas,

			  snd_pcm_uframes_t dst_offset,

			  const snd_pcm_channel_area_t *src_areas,

			  snd_pcm_uframes_t src_offset,

			  unsigned int channels, snd_pcm_uframes_t frames,

			  unsigned int getidx,

			  snd_pcm_adpcm_state_t *states)

{

#define GET16_LABELS

#include "plugin_ops.h"

#undef GET16_LABELS

	void *get = get16_labels[getidx];

	unsigned int channel;

	int16_t sample = 0;

	for (channel = 0; channel < channels; ++channel, ++states) {

		const char *src;

		char *dst;

		int dstbit;

		int src_step, dst_step, dstbit_step;

		snd_pcm_uframes_t frames1;

		const snd_pcm_channel_area_t *src_area = &src_areas[channel];

		const snd_pcm_channel_area_t *dst_area = &dst_areas[channel];

		src = snd_pcm_channel_area_addr(src_area, src_offset);

		src_step = snd_pcm_channel_area_step(src_area);

		dstbit = dst_area->first + dst_area->step * dst_offset;

		dst = (char *) dst_area->addr + dstbit / 8;

		dstbit %= 8;

		dst_step = dst_area->step / 8;

		dstbit_step = dst_area->step % 8;

		frames1 = frames;

		while (frames1-- > 0) {

			int v;

			goto *get;

#define GET16_END after

#include "plugin_ops.h"

#undef GET16_END

		after:

			v = adpcm_encoder(sample, states);

			if (dstbit)

				*dst = (*dst & 0xf0) | v;

			else

				*dst = (*dst & 0x0f) | (v << 4);

			src += src_step;

			dst += dst_step;

			dstbit += dstbit_step;

			if (dstbit == 8) {

				dst++;

				dstbit = 0;

			}

		}

	}

}

#endif

static int snd_pcm_adpcm_hw_refine_cprepare(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	int err;

	snd_pcm_access_mask_t access_mask = { SND_PCM_ACCBIT_SHM };

	err = _snd_pcm_hw_param_set_mask(params, SND_PCM_HW_PARAM_ACCESS,

					 &access_mask);

	if (err < 0)

		return err;

	if (adpcm->sformat == SND_PCM_FORMAT_IMA_ADPCM) {

		snd_pcm_format_mask_t format_mask = { SND_PCM_FMTBIT_LINEAR };

		err = _snd_pcm_hw_param_set_mask(params, SND_PCM_HW_PARAM_FORMAT,

						 &format_mask);

	} else {

		err = _snd_pcm_hw_params_set_format(params,

						   SND_PCM_FORMAT_IMA_ADPCM);

	}

	if (err < 0)

		return err;

	err = _snd_pcm_hw_params_set_subformat(params,

					       SND_PCM_SUBFORMAT_STD);

	if (err < 0)

		return err;

	params->info &= ~(SND_PCM_INFO_MMAP | SND_PCM_INFO_MMAP_VALID);

	return 0;

}

static int snd_pcm_adpcm_hw_refine_sprepare(snd_pcm_t *pcm, snd_pcm_hw_params_t *sparams)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	snd_pcm_access_mask_t saccess_mask = { SND_PCM_ACCBIT_MMAP };

	_snd_pcm_hw_params_any(sparams);

	_snd_pcm_hw_param_set_mask(sparams, SND_PCM_HW_PARAM_ACCESS,

				   &saccess_mask);

	_snd_pcm_hw_params_set_format(sparams, adpcm->sformat);

	_snd_pcm_hw_params_set_subformat(sparams, SND_PCM_SUBFORMAT_STD);

	return 0;

}

static int snd_pcm_adpcm_hw_refine_schange(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_hw_params_t *params,

					    snd_pcm_hw_params_t *sparams)

{

	int err;

	unsigned int links = (SND_PCM_HW_PARBIT_CHANNELS |

			      SND_PCM_HW_PARBIT_RATE |

			      SND_PCM_HW_PARBIT_PERIOD_SIZE |

			      SND_PCM_HW_PARBIT_BUFFER_SIZE |

			      SND_PCM_HW_PARBIT_PERIODS |

			      SND_PCM_HW_PARBIT_PERIOD_TIME |

			      SND_PCM_HW_PARBIT_BUFFER_TIME |

			      SND_PCM_HW_PARBIT_TICK_TIME);

	err = _snd_pcm_hw_params_refine(sparams, links, params);

	if (err < 0)

		return err;

	return 0;

}

static int snd_pcm_adpcm_hw_refine_cchange(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_hw_params_t *params,

					    snd_pcm_hw_params_t *sparams)

{

	int err;

	unsigned int links = (SND_PCM_HW_PARBIT_CHANNELS |

			      SND_PCM_HW_PARBIT_RATE |

			      SND_PCM_HW_PARBIT_PERIOD_SIZE |

			      SND_PCM_HW_PARBIT_BUFFER_SIZE |

			      SND_PCM_HW_PARBIT_PERIODS |

			      SND_PCM_HW_PARBIT_PERIOD_TIME |

			      SND_PCM_HW_PARBIT_BUFFER_TIME |

			      SND_PCM_HW_PARBIT_TICK_TIME);

	err = _snd_pcm_hw_params_refine(params, links, sparams);

	if (err < 0)

		return err;

	return 0;

}

static int snd_pcm_adpcm_hw_refine(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)

{

	return snd_pcm_hw_refine_slave(pcm, params,

				       snd_pcm_adpcm_hw_refine_cprepare,

				       snd_pcm_adpcm_hw_refine_cchange,

				       snd_pcm_adpcm_hw_refine_sprepare,

				       snd_pcm_adpcm_hw_refine_schange,

				       snd_pcm_generic_hw_refine);

}

static int snd_pcm_adpcm_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	snd_pcm_format_t format;

	int err = snd_pcm_hw_params_slave(pcm, params,

					  snd_pcm_adpcm_hw_refine_cchange,

					  snd_pcm_adpcm_hw_refine_sprepare,

					  snd_pcm_adpcm_hw_refine_schange,

					  snd_pcm_generic_hw_params);

	if (err < 0)

		return err;

	err = INTERNAL(snd_pcm_hw_params_get_format)(params, &format);

	if (err < 0)

		return err;

	if (pcm->stream == SND_PCM_STREAM_PLAYBACK) {

		if (adpcm->sformat == SND_PCM_FORMAT_IMA_ADPCM) {

			adpcm->getput_idx = snd_pcm_linear_get_index(format, SND_PCM_FORMAT_S16);

			adpcm->func = snd_pcm_adpcm_encode;

		} else {

			adpcm->getput_idx = snd_pcm_linear_put_index(SND_PCM_FORMAT_S16, adpcm->sformat);

			adpcm->func = snd_pcm_adpcm_decode;

		}

	} else {

		if (adpcm->sformat == SND_PCM_FORMAT_IMA_ADPCM) {

			adpcm->getput_idx = snd_pcm_linear_put_index(SND_PCM_FORMAT_S16, format);

			adpcm->func = snd_pcm_adpcm_decode;

		} else {

			adpcm->getput_idx = snd_pcm_linear_get_index(adpcm->sformat, SND_PCM_FORMAT_S16);

			adpcm->func = snd_pcm_adpcm_encode;

		}

	}

	assert(!adpcm->states);

	adpcm->states = malloc(adpcm->plug.gen.slave->channels * sizeof(*adpcm->states));

	if (adpcm->states == NULL)

		return -ENOMEM;

	return 0;

}

static int snd_pcm_adpcm_hw_free(snd_pcm_t *pcm)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	free(adpcm->states);

	adpcm->states = NULL;

	return snd_pcm_hw_free(adpcm->plug.gen.slave);

}

static int snd_pcm_adpcm_init(snd_pcm_t *pcm)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	unsigned int k;

	for (k = 0; k < pcm->channels; ++k) {

		adpcm->states[k].pred_val = 0;

		adpcm->states[k].step_idx = 0;

	}

	return 0;

}

static snd_pcm_uframes_t

snd_pcm_adpcm_write_areas(snd_pcm_t *pcm,

			  const snd_pcm_channel_area_t *areas,

			  snd_pcm_uframes_t offset,

			  snd_pcm_uframes_t size,

			  const snd_pcm_channel_area_t *slave_areas,

			  snd_pcm_uframes_t slave_offset,

			  snd_pcm_uframes_t *slave_sizep)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	if (size > *slave_sizep)

		size = *slave_sizep;

	adpcm->func(slave_areas, slave_offset,

		    areas, offset, 

		    pcm->channels, size,

		    adpcm->getput_idx, adpcm->states);

	*slave_sizep = size;

	return size;

}

static snd_pcm_uframes_t

snd_pcm_adpcm_read_areas(snd_pcm_t *pcm,

			 const snd_pcm_channel_area_t *areas,

			 snd_pcm_uframes_t offset,

			 snd_pcm_uframes_t size,

			 const snd_pcm_channel_area_t *slave_areas,

			 snd_pcm_uframes_t slave_offset,

			 snd_pcm_uframes_t *slave_sizep)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	if (size > *slave_sizep)

		size = *slave_sizep;

	adpcm->func(areas, offset, 

		    slave_areas, slave_offset,

		    pcm->channels, size,

		    adpcm->getput_idx, adpcm->states);

	*slave_sizep = size;

	return size;

}

static void snd_pcm_adpcm_dump(snd_pcm_t *pcm, snd_output_t *out)

{

	snd_pcm_adpcm_t *adpcm = pcm->private_data;

	snd_output_printf(out, "Ima-ADPCM conversion PCM (%s)\n", 

		snd_pcm_format_name(adpcm->sformat));

	if (pcm->setup) {

		snd_output_printf(out, "Its setup is:\n");

		snd_pcm_dump_setup(pcm, out);

	}

	snd_output_printf(out, "Slave: ");

	snd_pcm_dump(adpcm->plug.gen.slave, out);

}

static const snd_pcm_ops_t snd_pcm_adpcm_ops = {

	.close = snd_pcm_generic_close,

	.info = snd_pcm_generic_info,

	.hw_refine = snd_pcm_adpcm_hw_refine,

	.hw_params = snd_pcm_adpcm_hw_params,

	.hw_free = snd_pcm_adpcm_hw_free,

	.sw_params = snd_pcm_generic_sw_params,

	.channel_info = snd_pcm_generic_channel_info,

	.dump = snd_pcm_adpcm_dump,

	.nonblock = snd_pcm_generic_nonblock,

	.async = snd_pcm_generic_async,

	.mmap = snd_pcm_generic_mmap,

	.munmap = snd_pcm_generic_munmap,

	.query_chmaps = snd_pcm_generic_query_chmaps,

	.get_chmap = snd_pcm_generic_get_chmap,

	.set_chmap = snd_pcm_generic_set_chmap,

};

/**

 * \brief Creates a new Ima-ADPCM conversion PCM

 * \param pcmp Returns created PCM handle

 * \param name Name of PCM

 * \param sformat Slave (destination) format

 * \param slave Slave PCM handle

 * \param close_slave When set, the slave PCM handle is closed with copy PCM

 * \retval zero on success otherwise a negative error code

 * \warning Using of this function might be dangerous in the sense

 *          of compatibility reasons. The prototype might be freely

 *          changed in future.

 */

int snd_pcm_adpcm_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sformat, snd_pcm_t *slave, int close_slave)

{

	snd_pcm_t *pcm;

	snd_pcm_adpcm_t *adpcm;

	int err;

	assert(pcmp && slave);

	if (snd_pcm_format_linear(sformat) != 1 &&

	    sformat != SND_PCM_FORMAT_IMA_ADPCM)

		return -EINVAL;

	adpcm = calloc(1, sizeof(snd_pcm_adpcm_t));

	if (!adpcm) {

		return -ENOMEM;

	}

	adpcm->sformat = sformat;

	snd_pcm_plugin_init(&adpcm->plug);

	adpcm->plug.read = snd_pcm_adpcm_read_areas;

	adpcm->plug.write = snd_pcm_adpcm_write_areas;

	adpcm->plug.init = snd_pcm_adpcm_init;

	adpcm->plug.gen.slave = slave;

	adpcm->plug.gen.close_slave = close_slave;

	err = snd_pcm_new(&pcm, SND_PCM_TYPE_ADPCM, name, slave->stream, slave->mode);

	if (err < 0) {

		free(adpcm);

		return err;

	}

	pcm->ops = &snd_pcm_adpcm_ops;

	pcm->fast_ops = &snd_pcm_plugin_fast_ops;

	pcm->private_data = adpcm;

	pcm->poll_fd = slave->poll_fd;

	pcm->poll_events = slave->poll_events;

	pcm->tstamp_type = slave->tstamp_type;

	snd_pcm_set_hw_ptr(pcm, &adpcm->plug.hw_ptr, -1, 0);

	snd_pcm_set_appl_ptr(pcm, &adpcm->plug.appl_ptr, -1, 0);

	*pcmp = pcm;

	return 0;

}

/*! \page pcm_plugins

\section pcm_plugins_adpcm Plugin: Ima-ADPCM

This plugin converts Ima-ADPCM samples to linear or linear to Ima-ADPCM samples

from master Ima-ADPCM conversion PCM to given slave PCM. The channel count,

format and rate must match for both of them.

\code

pcm.name {

        type adpcm              # Ima-ADPCM conversion PCM

        slave STR               # Slave name

        # or

        slave {                 # Slave definition

                pcm STR         # Slave PCM name

                # or

                pcm { }         # Slave PCM definition

                format STR      # Slave format

        }

}

\endcode

\subsection pcm_plugins_adpcm_funcref Function reference

  
snd_pcm_adpcm_open()

  
_snd_pcm_adpcm_open()

*/

/**

 * \brief Creates a new Ima-ADPCM conversion PCM

 * \param pcmp Returns created PCM handle

 * \param name Name of PCM

 * \param root Root configuration node

 * \param conf Configuration node with copy PCM description

 * \param stream Stream type

 * \param mode Stream mode

 * \retval zero on success otherwise a negative error code

 * \warning Using of this function might be dangerous in the sense

 *          of compatibility reasons. The prototype might be freely

 *          changed in future.

 */

int _snd_pcm_adpcm_open(snd_pcm_t **pcmp, const char *name,

			snd_config_t *root, snd_config_t *conf, 

			snd_pcm_stream_t stream, int mode)

{

	snd_config_iterator_t i, next;

	int err;

	snd_pcm_t *spcm;

	snd_config_t *slave = NULL, *sconf;

	snd_pcm_format_t sformat;

	snd_config_for_each(i, next, conf) {

		snd_config_t *n = snd_config_iterator_entry(i);

		const char *id;

		if (snd_config_get_id(n, &id) < 0)

			continue;

		if (snd_pcm_conf_generic_id(id))

			continue;

		if (strcmp(id, "slave") == 0) {

			slave = n;

			continue;

		}

		SNDERR("Unknown field %s", id);

		return -EINVAL;

	}

	if (!slave) {

		SNDERR("slave is not defined");

		return -EINVAL;

	}

	err = snd_pcm_slave_conf(root, slave, &sconf, 1,

				 SND_PCM_HW_PARAM_FORMAT, SCONF_MANDATORY, &sformat);

	if (err < 0)

		return err;

	if (snd_pcm_format_linear(sformat) != 1 &&

	    sformat != SND_PCM_FORMAT_IMA_ADPCM) {

	    	snd_config_delete(sconf);

		SNDERR("invalid slave format");

		return -EINVAL;

	}

	err = snd_pcm_open_slave(&spcm, root, sconf, stream, mode, conf);

	snd_config_delete(sconf);

	if (err < 0)

		return err;

	err = snd_pcm_adpcm_open(pcmp, name, sformat, spcm, 1);

	if (err < 0)

		snd_pcm_close(spcm);

	return err;

}

#ifndef DOC_HIDDEN

SND_DLSYM_BUILD_VERSION(_snd_pcm_adpcm_open, SND_PCM_DLSYM_VERSION);

#endif