text: /*
   *  PCM Plug-In shared (kernel/library) code
   *  Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz>
   *  Copyright (c) 2000 by Abramo Bagnara <abramo@alsa-project.org>
   *
   *
   *   This library is free software; you can redistribute it and/or modify
   *   it under the terms of the GNU Library General Public License as
   *   published by the Free Software Foundation; either version 2 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 Library General Public License for more details.
   *
   *   You should have received a copy of the GNU Library General Public
   *   License along with this library; if not, write to the Free Software
   *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
   *
   */
    
  #if 0
  #define PLUGIN_DEBUG
  #endif
  
  #include <linux/slab.h>
  #include <linux/time.h>
  #include <linux/vmalloc.h>
  #include <sound/core.h>
  #include <sound/pcm.h>
  #include <sound/pcm_params.h>
  #include "pcm_plugin.h"
  
  #define snd_pcm_plug_first(plug) ((plug)->runtime->oss.plugin_first)
  #define snd_pcm_plug_last(plug) ((plug)->runtime->oss.plugin_last)
  
  /*
   *  because some cards might have rates "very close", we ignore
   *  all "resampling" requests within +-5%
   */
  static int rate_match(unsigned int src_rate, unsigned int dst_rate)
  {
  	unsigned int low = (src_rate * 95) / 100;
  	unsigned int high = (src_rate * 105) / 100;
  	return dst_rate >= low && dst_rate <= high;
  }
  
  static int snd_pcm_plugin_alloc(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t frames)
  {
  	struct snd_pcm_plugin_format *format;
  	ssize_t width;
  	size_t size;
  	unsigned int channel;
  	struct snd_pcm_plugin_channel *c;
  
  	if (plugin->stream == SNDRV_PCM_STREAM_PLAYBACK) {
  		format = &plugin->src_format;
  	} else {
  		format = &plugin->dst_format;
  	}
  	width = snd_pcm_format_physical_width(format->format);
  	if (width < 0)
  		return width;
  	size = frames * format->channels * width;
  	if (snd_BUG_ON(size % 8))
  		return -ENXIO;
  	size /= 8;
  	if (plugin->buf_frames < frames) {
  		kvfree(plugin->buf);
  		plugin->buf = kvzalloc(size, GFP_KERNEL);
  		plugin->buf_frames = frames;
  	}
  	if (!plugin->buf) {
  		plugin->buf_frames = 0;
  		return -ENOMEM;
  	}
  	c = plugin->buf_channels;
  	if (plugin->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED) {
  		for (channel = 0; channel < format->channels; channel++, c++) {
  			c->frames = frames;
  			c->enabled = 1;
  			c->wanted = 0;
  			c->area.addr = plugin->buf;
  			c->area.first = channel * width;
  			c->area.step = format->channels * width;
  		}
  	} else if (plugin->access == SNDRV_PCM_ACCESS_RW_NONINTERLEAVED) {
  		if (snd_BUG_ON(size % format->channels))
  			return -EINVAL;
  		size /= format->channels;
  		for (channel = 0; channel < format->channels; channel++, c++) {
  			c->frames = frames;
  			c->enabled = 1;
  			c->wanted = 0;
  			c->area.addr = plugin->buf + (channel * size);
  			c->area.first = 0;
  			c->area.step = width;
  		}
  	} else
  		return -EINVAL;
  	return 0;
  }
  
  int snd_pcm_plug_alloc(struct snd_pcm_substream *plug, snd_pcm_uframes_t frames)
  {
  	int err;
  	if (snd_BUG_ON(!snd_pcm_plug_first(plug)))
  		return -ENXIO;
  	if (snd_pcm_plug_stream(plug) == SNDRV_PCM_STREAM_PLAYBACK) {
  		struct snd_pcm_plugin *plugin = snd_pcm_plug_first(plug);
  		while (plugin->next) {
  			if (plugin->dst_frames)
  				frames = plugin->dst_frames(plugin, frames);
  			if ((snd_pcm_sframes_t)frames <= 0)
  				return -ENXIO;
  			plugin = plugin->next;
  			err = snd_pcm_plugin_alloc(plugin, frames);
  			if (err < 0)
  				return err;
  		}
  	} else {
  		struct snd_pcm_plugin *plugin = snd_pcm_plug_last(plug);
  		while (plugin->prev) {
  			if (plugin->src_frames)
  				frames = plugin->src_frames(plugin, frames);
  			if ((snd_pcm_sframes_t)frames <= 0)
  				return -ENXIO;
  			plugin = plugin->prev;
  			err = snd_pcm_plugin_alloc(plugin, frames);
  			if (err < 0)
  				return err;
  		}
  	}
  	return 0;
  }
  
  
  snd_pcm_sframes_t snd_pcm_plugin_client_channels(struct snd_pcm_plugin *plugin,
  				       snd_pcm_uframes_t frames,
  				       struct snd_pcm_plugin_channel **channels)
  {
  	*channels = plugin->buf_channels;
  	return frames;
  }
  
  int snd_pcm_plugin_build(struct snd_pcm_substream *plug,
  			 const char *name,
  			 struct snd_pcm_plugin_format *src_format,
  			 struct snd_pcm_plugin_format *dst_format,
  			 size_t extra,
  			 struct snd_pcm_plugin **ret)
  {
  	struct snd_pcm_plugin *plugin;
  	unsigned int channels;
  	
  	if (snd_BUG_ON(!plug))
  		return -ENXIO;
  	if (snd_BUG_ON(!src_format || !dst_format))
  		return -ENXIO;
  	plugin = kzalloc(sizeof(*plugin) + extra, GFP_KERNEL);
  	if (plugin == NULL)
  		return -ENOMEM;
  	plugin->name = name;
  	plugin->plug = plug;
  	plugin->stream = snd_pcm_plug_stream(plug);
  	plugin->access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
  	plugin->src_format = *src_format;
  	plugin->src_width = snd_pcm_format_physical_width(src_format->format);
  	snd_BUG_ON(plugin->src_width <= 0);
  	plugin->dst_format = *dst_format;
  	plugin->dst_width = snd_pcm_format_physical_width(dst_format->format);
  	snd_BUG_ON(plugin->dst_width <= 0);
  	if (plugin->stream == SNDRV_PCM_STREAM_PLAYBACK)
  		channels = src_format->channels;
  	else
  		channels = dst_format->channels;
  	plugin->buf_channels = kcalloc(channels, sizeof(*plugin->buf_channels), GFP_KERNEL);
  	if (plugin->buf_channels == NULL) {
  		snd_pcm_plugin_free(plugin);
  		return -ENOMEM;
  	}
  	plugin->client_channels = snd_pcm_plugin_client_channels;
  	*ret = plugin;
  	return 0;
  }
  
  int snd_pcm_plugin_free(struct snd_pcm_plugin *plugin)
  {
  	if (! plugin)
  		return 0;
  	if (plugin->private_free)
  		plugin->private_free(plugin);
  	kfree(plugin->buf_channels);
  	kvfree(plugin->buf);
  	kfree(plugin);
  	return 0;
  }
  
  static snd_pcm_sframes_t calc_dst_frames(struct snd_pcm_substream *plug,
  					 snd_pcm_sframes_t frames,
  					 bool check_size)
  {
  	struct snd_pcm_plugin *plugin, *plugin_next;
  
  	plugin = snd_pcm_plug_first(plug);
  	while (plugin && frames > 0) {
  		plugin_next = plugin->next;
  		if (check_size && plugin->buf_frames &&
  		    frames > plugin->buf_frames)
  			frames = plugin->buf_frames;
  		if (plugin->dst_frames) {
  			frames = plugin->dst_frames(plugin, frames);
  			if (frames < 0)
  				return frames;
  		}
  		plugin = plugin_next;
  	}
  	return frames;
  }
  
  static snd_pcm_sframes_t calc_src_frames(struct snd_pcm_substream *plug,
  					 snd_pcm_sframes_t frames,
  					 bool check_size)
  {
  	struct snd_pcm_plugin *plugin, *plugin_prev;
  
  	plugin = snd_pcm_plug_last(plug);
  	while (plugin && frames > 0) {
  		plugin_prev = plugin->prev;
  		if (plugin->src_frames) {
  			frames = plugin->src_frames(plugin, frames);
  			if (frames < 0)
  				return frames;
  		}
  		if (check_size && plugin->buf_frames &&
  		    frames > plugin->buf_frames)
  			frames = plugin->buf_frames;
  		plugin = plugin_prev;
  	}
  	return frames;
  }
  
  snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *plug, snd_pcm_uframes_t drv_frames)
  {
  	if (snd_BUG_ON(!plug))
  		return -ENXIO;
  	switch (snd_pcm_plug_stream(plug)) {
  	case SNDRV_PCM_STREAM_PLAYBACK:
  		return calc_src_frames(plug, drv_frames, false);
  	case SNDRV_PCM_STREAM_CAPTURE:
  		return calc_dst_frames(plug, drv_frames, false);
  	default:
  		snd_BUG();
  		return -EINVAL;
  	}
  }
  
  snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *plug, snd_pcm_uframes_t clt_frames)
  {
  	if (snd_BUG_ON(!plug))
  		return -ENXIO;
  	switch (snd_pcm_plug_stream(plug)) {
  	case SNDRV_PCM_STREAM_PLAYBACK:
  		return calc_dst_frames(plug, clt_frames, false);
  	case SNDRV_PCM_STREAM_CAPTURE:
  		return calc_src_frames(plug, clt_frames, false);
  	default:
  		snd_BUG();
  		return -EINVAL;
  	}
  }
  
  static int snd_pcm_plug_formats(const struct snd_mask *mask,
  				snd_pcm_format_t format)
  {
  	struct snd_mask formats = *mask;
  	u64 linfmts = (SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S8 |
  		       SNDRV_PCM_FMTBIT_U16_LE | SNDRV_PCM_FMTBIT_S16_LE |
  		       SNDRV_PCM_FMTBIT_U16_BE | SNDRV_PCM_FMTBIT_S16_BE |
  		       SNDRV_PCM_FMTBIT_U24_LE | SNDRV_PCM_FMTBIT_S24_LE |
  		       SNDRV_PCM_FMTBIT_U24_BE | SNDRV_PCM_FMTBIT_S24_BE |
  		       SNDRV_PCM_FMTBIT_U24_3LE | SNDRV_PCM_FMTBIT_S24_3LE |
  		       SNDRV_PCM_FMTBIT_U24_3BE | SNDRV_PCM_FMTBIT_S24_3BE |
  		       SNDRV_PCM_FMTBIT_U32_LE | SNDRV_PCM_FMTBIT_S32_LE |
  		       SNDRV_PCM_FMTBIT_U32_BE | SNDRV_PCM_FMTBIT_S32_BE);
  	snd_mask_set(&formats, (__force int)SNDRV_PCM_FORMAT_MU_LAW);
  	
  	if (formats.bits[0] & lower_32_bits(linfmts))
  		formats.bits[0] |= lower_32_bits(linfmts);
  	if (formats.bits[1] & upper_32_bits(linfmts))
  		formats.bits[1] |= upper_32_bits(linfmts);
  	return snd_mask_test(&formats, (__force int)format);
  }
  
  static const snd_pcm_format_t preferred_formats[] = {
  	SNDRV_PCM_FORMAT_S16_LE,
  	SNDRV_PCM_FORMAT_S16_BE,
  	SNDRV_PCM_FORMAT_U16_LE,
  	SNDRV_PCM_FORMAT_U16_BE,
  	SNDRV_PCM_FORMAT_S24_3LE,
  	SNDRV_PCM_FORMAT_S24_3BE,
  	SNDRV_PCM_FORMAT_U24_3LE,
  	SNDRV_PCM_FORMAT_U24_3BE,
  	SNDRV_PCM_FORMAT_S24_LE,
  	SNDRV_PCM_FORMAT_S24_BE,
  	SNDRV_PCM_FORMAT_U24_LE,
  	SNDRV_PCM_FORMAT_U24_BE,
  	SNDRV_PCM_FORMAT_S32_LE,
  	SNDRV_PCM_FORMAT_S32_BE,
  	SNDRV_PCM_FORMAT_U32_LE,
  	SNDRV_PCM_FORMAT_U32_BE,
  	SNDRV_PCM_FORMAT_S8,
  	SNDRV_PCM_FORMAT_U8
  };
  
  snd_pcm_format_t snd_pcm_plug_slave_format(snd_pcm_format_t format,
  					   const struct snd_mask *format_mask)
  {
  	int i;
  
  	if (snd_mask_test(format_mask, (__force int)format))
  		return format;
  	if (!snd_pcm_plug_formats(format_mask, format))
  		return (__force snd_pcm_format_t)-EINVAL;
  	if (snd_pcm_format_linear(format)) {
  		unsigned int width = snd_pcm_format_width(format);
  		int unsignd = snd_pcm_format_unsigned(format) > 0;
  		int big = snd_pcm_format_big_endian(format) > 0;
  		unsigned int badness, best = -1;
  		snd_pcm_format_t best_format = (__force snd_pcm_format_t)-1;
  		for (i = 0; i < ARRAY_SIZE(preferred_formats); i++) {
  			snd_pcm_format_t f = preferred_formats[i];
  			unsigned int w;
  			if (!snd_mask_test(format_mask, (__force int)f))
  				continue;
  			w = snd_pcm_format_width(f);
  			if (w >= width)
  				badness = w - width;
  			else
  				badness = width - w + 32;
  			badness += snd_pcm_format_unsigned(f) != unsignd;
  			badness += snd_pcm_format_big_endian(f) != big;
  			if (badness < best) {
  				best_format = f;
  				best = badness;
  			}
  		}
  		if ((__force int)best_format >= 0)
  			return best_format;
  		else
  			return (__force snd_pcm_format_t)-EINVAL;
  	} else {
  		switch (format) {
  		case SNDRV_PCM_FORMAT_MU_LAW:
  			for (i = 0; i < ARRAY_SIZE(preferred_formats); ++i) {
  				snd_pcm_format_t format1 = preferred_formats[i];
  				if (snd_mask_test(format_mask, (__force int)format1))
  					return format1;
  			}
  			fallthrough;
  		default:
  			return (__force snd_pcm_format_t)-EINVAL;
  		}
  	}
  }
  
  int snd_pcm_plug_format_plugins(struct snd_pcm_substream *plug,
  				struct snd_pcm_hw_params *params,
  				struct snd_pcm_hw_params *slave_params)
  {
  	struct snd_pcm_plugin_format tmpformat;
  	struct snd_pcm_plugin_format dstformat;
  	struct snd_pcm_plugin_format srcformat;
  	snd_pcm_access_t src_access, dst_access;
  	struct snd_pcm_plugin *plugin = NULL;
  	int err;
  	int stream = snd_pcm_plug_stream(plug);
  	int slave_interleaved = (params_channels(slave_params) == 1 ||
  				 params_access(slave_params) == SNDRV_PCM_ACCESS_RW_INTERLEAVED);
  
  	switch (stream) {
  	case SNDRV_PCM_STREAM_PLAYBACK:
  		dstformat.format = params_format(slave_params);
  		dstformat.rate = params_rate(slave_params);
  		dstformat.channels = params_channels(slave_params);
  		srcformat.format = params_format(params);
  		srcformat.rate = params_rate(params);
  		srcformat.channels = params_channels(params);
  		src_access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
  		dst_access = (slave_interleaved ? SNDRV_PCM_ACCESS_RW_INTERLEAVED :
  						  SNDRV_PCM_ACCESS_RW_NONINTERLEAVED);
  		break;
  	case SNDRV_PCM_STREAM_CAPTURE:
  		dstformat.format = params_format(params);
  		dstformat.rate = params_rate(params);
  		dstformat.channels = params_channels(params);
  		srcformat.format = params_format(slave_params);
  		srcformat.rate = params_rate(slave_params);
  		srcformat.channels = params_channels(slave_params);
  		src_access = (slave_interleaved ? SNDRV_PCM_ACCESS_RW_INTERLEAVED :
  						  SNDRV_PCM_ACCESS_RW_NONINTERLEAVED);
  		dst_access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
  		break;
  	default:
  		snd_BUG();
  		return -EINVAL;
  	}
  	tmpformat = srcformat;
  		
  	pdprintf("srcformat: format=%i, rate=%i, channels=%i\n", 
  		 srcformat.format,
  		 srcformat.rate,
  		 srcformat.channels);
  	pdprintf("dstformat: format=%i, rate=%i, channels=%i\n", 
  		 dstformat.format,
  		 dstformat.rate,
  		 dstformat.channels);
  
  	/* Format change (linearization) */
  	if (! rate_match(srcformat.rate, dstformat.rate) &&
  	    ! snd_pcm_format_linear(srcformat.format)) {
  		if (srcformat.format != SNDRV_PCM_FORMAT_MU_LAW)
  			return -EINVAL;
  		tmpformat.format = SNDRV_PCM_FORMAT_S16;
  		err = snd_pcm_plugin_build_mulaw(plug,
  						 &srcformat, &tmpformat,
  						 &plugin);
  		if (err < 0)
  			return err;
  		err = snd_pcm_plugin_append(plugin);
  		if (err < 0) {
  			snd_pcm_plugin_free(plugin);
  			return err;
  		}
  		srcformat = tmpformat;
  		src_access = dst_access;
  	}
  
  	/* channels reduction */
  	if (srcformat.channels > dstformat.channels) {
  		tmpformat.channels = dstformat.channels;
  		err = snd_pcm_plugin_build_route(plug, &srcformat, &tmpformat, &plugin);
  		pdprintf("channels reduction: src=%i, dst=%i returns %i\n", srcformat.channels, tmpformat.channels, err);
  		if (err < 0)
  			return err;
  		err = snd_pcm_plugin_append(plugin);
  		if (err < 0) {
  			snd_pcm_plugin_free(plugin);
  			return err;
  		}
  		srcformat = tmpformat;
  		src_access = dst_access;
  	}
  
  	/* rate resampling */
  	if (!rate_match(srcformat.rate, dstformat.rate)) {
  		if (srcformat.format != SNDRV_PCM_FORMAT_S16) {
  			/* convert to S16 for resampling */
  			tmpformat.format = SNDRV_PCM_FORMAT_S16;
  			err = snd_pcm_plugin_build_linear(plug,
  							  &srcformat, &tmpformat,
  							  &plugin);
  			if (err < 0)
  				return err;
  			err = snd_pcm_plugin_append(plugin);
  			if (err < 0) {
  				snd_pcm_plugin_free(plugin);
  				return err;
  			}
  			srcformat = tmpformat;
  			src_access = dst_access;
  		}
  		tmpformat.rate = dstformat.rate;
          	err = snd_pcm_plugin_build_rate(plug,
          					&srcformat, &tmpformat,
  						&plugin);
  		pdprintf("rate down resampling: src=%i, dst=%i returns %i\n", srcformat.rate, tmpformat.rate, err);
  		if (err < 0)
  			return err;
  		err = snd_pcm_plugin_append(plugin);
  		if (err < 0) {
  			snd_pcm_plugin_free(plugin);
  			return err;
  		}
  		srcformat = tmpformat;
  		src_access = dst_access;
          }
  
  	/* format change */
  	if (srcformat.format != dstformat.format) {
  		tmpformat.format = dstformat.format;
  		if (srcformat.format == SNDRV_PCM_FORMAT_MU_LAW ||
  		    tmpformat.format == SNDRV_PCM_FORMAT_MU_LAW) {
  			err = snd_pcm_plugin_build_mulaw(plug,
  							 &srcformat, &tmpformat,
  							 &plugin);
  		}
  		else if (snd_pcm_format_linear(srcformat.format) &&
  			 snd_pcm_format_linear(tmpformat.format)) {
  			err = snd_pcm_plugin_build_linear(plug,
  							  &srcformat, &tmpformat,
  							  &plugin);
  		}
  		else
  			return -EINVAL;
  		pdprintf("format change: src=%i, dst=%i returns %i\n", srcformat.format, tmpformat.format, err);
  		if (err < 0)
  			return err;
  		err = snd_pcm_plugin_append(plugin);
  		if (err < 0) {
  			snd_pcm_plugin_free(plugin);
  			return err;
  		}
  		srcformat = tmpformat;
  		src_access = dst_access;
  	}
  
  	/* channels extension */
  	if (srcformat.channels < dstformat.channels) {
  		tmpformat.channels = dstformat.channels;
  		err = snd_pcm_plugin_build_route(plug, &srcformat, &tmpformat, &plugin);
  		pdprintf("channels extension: src=%i, dst=%i returns %i\n", srcformat.channels, tmpformat.channels, err);
  		if (err < 0)
  			return err;
  		err = snd_pcm_plugin_append(plugin);
  		if (err < 0) {
  			snd_pcm_plugin_free(plugin);
  			return err;
  		}
  		srcformat = tmpformat;
  		src_access = dst_access;
  	}
  
  	/* de-interleave */
  	if (src_access != dst_access) {
  		err = snd_pcm_plugin_build_copy(plug,
  						&srcformat,
  						&tmpformat,
  						&plugin);
  		pdprintf("interleave change (copy: returns %i)\n", err);
  		if (err < 0)
  			return err;
  		err = snd_pcm_plugin_append(plugin);
  		if (err < 0) {
  			snd_pcm_plugin_free(plugin);
  			return err;
  		}
  	}
  
  	return 0;
  }
  
  snd_pcm_sframes_t snd_pcm_plug_client_channels_buf(struct snd_pcm_substream *plug,
  					 char *buf,
  					 snd_pcm_uframes_t count,
  					 struct snd_pcm_plugin_channel **channels)
  {
  	struct snd_pcm_plugin *plugin;
  	struct snd_pcm_plugin_channel *v;
  	struct snd_pcm_plugin_format *format;
  	int width, nchannels, channel;
  	int stream = snd_pcm_plug_stream(plug);
  
  	if (snd_BUG_ON(!buf))
  		return -ENXIO;
  	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
  		plugin = snd_pcm_plug_first(plug);
  		format = &plugin->src_format;
  	} else {
  		plugin = snd_pcm_plug_last(plug);
  		format = &plugin->dst_format;
  	}
  	v = plugin->buf_channels;
  	*channels = v;
  	width = snd_pcm_format_physical_width(format->format);
  	if (width < 0)
  		return width;
  	nchannels = format->channels;
  	if (snd_BUG_ON(plugin->access != SNDRV_PCM_ACCESS_RW_INTERLEAVED &&
  		       format->channels > 1))
  		return -ENXIO;
  	for (channel = 0; channel < nchannels; channel++, v++) {
  		v->frames = count;
  		v->enabled = 1;
  		v->wanted = (stream == SNDRV_PCM_STREAM_CAPTURE);
  		v->area.addr = buf;
  		v->area.first = channel * width;
  		v->area.step = nchannels * width;
  	}
  	return count;
  }
  
  snd_pcm_sframes_t snd_pcm_plug_write_transfer(struct snd_pcm_substream *plug, struct snd_pcm_plugin_channel *src_channels, snd_pcm_uframes_t size)
  {
  	struct snd_pcm_plugin *plugin, *next;
  	struct snd_pcm_plugin_channel *dst_channels;
  	int err;
  	snd_pcm_sframes_t frames = size;
  
  	plugin = snd_pcm_plug_first(plug);
  	while (plugin) {
  		if (frames <= 0)
  			return frames;
  		next = plugin->next;
  		if (next) {
  			snd_pcm_sframes_t frames1 = frames;
  			if (plugin->dst_frames) {
  				frames1 = plugin->dst_frames(plugin, frames);
  				if (frames1 <= 0)
  					return frames1;
  			}
  			err = next->client_channels(next, frames1, &dst_channels);
  			if (err < 0)
  				return err;
  			if (err != frames1) {
  				frames = err;
  				if (plugin->src_frames) {
  					frames = plugin->src_frames(plugin, frames1);
  					if (frames <= 0)
  						return frames;
  				}
  			}
  		} else
  			dst_channels = NULL;
  		pdprintf("write plugin: %s, %li\n", plugin->name, frames);
  		frames = plugin->transfer(plugin, src_channels, dst_channels, frames);
  		if (frames < 0)
  			return frames;
  		src_channels = dst_channels;
  		plugin = next;
  	}
  	return calc_src_frames(plug, frames, true);
  }
  
  snd_pcm_sframes_t snd_pcm_plug_read_transfer(struct snd_pcm_substream *plug, struct snd_pcm_plugin_channel *dst_channels_final, snd_pcm_uframes_t size)
  {
  	struct snd_pcm_plugin *plugin, *next;
  	struct snd_pcm_plugin_channel *src_channels, *dst_channels;
  	snd_pcm_sframes_t frames = size;
  	int err;
  
  	frames = calc_src_frames(plug, frames, true);
  	if (frames < 0)
  		return frames;
  
  	src_channels = NULL;
  	plugin = snd_pcm_plug_first(plug);
  	while (plugin && frames > 0) {
  		next = plugin->next;
  		if (next) {
  			err = plugin->client_channels(plugin, frames, &dst_channels);
  			if (err < 0)
  				return err;
  			frames = err;
  		} else {
  			dst_channels = dst_channels_final;
  		}
  		pdprintf("read plugin: %s, %li\n", plugin->name, frames);
  		frames = plugin->transfer(plugin, src_channels, dst_channels, frames);
  		if (frames < 0)
  			return frames;
  		plugin = next;
  		src_channels = dst_channels;
  	}
  	return frames;
  }
  
  int snd_pcm_area_silence(const struct snd_pcm_channel_area *dst_area, size_t dst_offset,
  			 size_t samples, snd_pcm_format_t format)
  {
  	/* FIXME: sub byte resolution and odd dst_offset */
  	unsigned char *dst;
  	unsigned int dst_step;
  	int width;
  	const unsigned char *silence;
  	if (!dst_area->addr)
  		return 0;
  	dst = dst_area->addr + (dst_area->first + dst_area->step * dst_offset) / 8;
  	width = snd_pcm_format_physical_width(format);
  	if (width <= 0)
  		return -EINVAL;
  	if (dst_area->step == (unsigned int) width && width >= 8)
  		return snd_pcm_format_set_silence(format, dst, samples);
  	silence = snd_pcm_format_silence_64(format);
  	if (! silence)
  		return -EINVAL;
  	dst_step = dst_area->step / 8;
  	if (width == 4) {
  		/* Ima ADPCM */
  		int dstbit = dst_area->first % 8;
  		int dstbit_step = dst_area->step % 8;
  		while (samples-- > 0) {
  			if (dstbit)
  				*dst &= 0xf0;
  			else
  				*dst &= 0x0f;
  			dst += dst_step;
  			dstbit += dstbit_step;
  			if (dstbit == 8) {
  				dst++;
  				dstbit = 0;
  			}
  		}
  	} else {
  		width /= 8;
  		while (samples-- > 0) {
  			memcpy(dst, silence, width);
  			dst += dst_step;
  		}
  	}
  	return 0;
  }
  
  int snd_pcm_area_copy(const struct snd_pcm_channel_area *src_area, size_t src_offset,
  		      const struct snd_pcm_channel_area *dst_area, size_t dst_offset,
  		      size_t samples, snd_pcm_format_t format)
  {
  	/* FIXME: sub byte resolution and odd dst_offset */
  	char *src, *dst;
  	int width;
  	int src_step, dst_step;
  	src = src_area->addr + (src_area->first + src_area->step * src_offset) / 8;
  	if (!src_area->addr)
  		return snd_pcm_area_silence(dst_area, dst_offset, samples, format);
  	dst = dst_area->addr + (dst_area->first + dst_area->step * dst_offset) / 8;
  	if (!dst_area->addr)
  		return 0;
  	width = snd_pcm_format_physical_width(format);
  	if (width <= 0)
  		return -EINVAL;
  	if (src_area->step == (unsigned int) width &&
  	    dst_area->step == (unsigned int) width && width >= 8) {
  		size_t bytes = samples * width / 8;
  		memcpy(dst, src, bytes);
  		return 0;
  	}
  	src_step = src_area->step / 8;
  	dst_step = dst_area->step / 8;
  	if (width == 4) {
  		/* Ima ADPCM */
  		int srcbit = src_area->first % 8;
  		int srcbit_step = src_area->step % 8;
  		int dstbit = dst_area->first % 8;
  		int dstbit_step = dst_area->step % 8;
  		while (samples-- > 0) {
  			unsigned char srcval;
  			if (srcbit)
  				srcval = *src & 0x0f;
  			else
  				srcval = (*src & 0xf0) >> 4;
  			if (dstbit)
  				*dst = (*dst & 0xf0) | srcval;
  			else
  				*dst = (*dst & 0x0f) | (srcval << 4);
  			src += src_step;
  			srcbit += srcbit_step;
  			if (srcbit == 8) {
  				src++;
  				srcbit = 0;
  			}
  			dst += dst_step;
  			dstbit += dstbit_step;
  			if (dstbit == 8) {
  				dst++;
  				dstbit = 0;
  			}
  		}
  	} else {
  		width /= 8;
  		while (samples-- > 0) {
  			memcpy(dst, src, width);
  			src += src_step;
  			dst += dst_step;
  		}
  	}
  	return 0;
  }
  