xref: /openbmc/linux/sound/core/oss/pcm_plugin.c (revision 643d1f7f)
1 /*
2  *  PCM Plug-In shared (kernel/library) code
3  *  Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz>
4  *  Copyright (c) 2000 by Abramo Bagnara <abramo@alsa-project.org>
5  *
6  *
7  *   This library is free software; you can redistribute it and/or modify
8  *   it under the terms of the GNU Library General Public License as
9  *   published by the Free Software Foundation; either version 2 of
10  *   the License, or (at your option) any later version.
11  *
12  *   This program is distributed in the hope that it will be useful,
13  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
14  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  *   GNU Library General Public License for more details.
16  *
17  *   You should have received a copy of the GNU Library General Public
18  *   License along with this library; if not, write to the Free Software
19  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
20  *
21  */
22 
23 #if 0
24 #define PLUGIN_DEBUG
25 #endif
26 
27 #include <linux/slab.h>
28 #include <linux/time.h>
29 #include <linux/vmalloc.h>
30 #include <sound/core.h>
31 #include <sound/pcm.h>
32 #include <sound/pcm_params.h>
33 #include "pcm_plugin.h"
34 
35 #define snd_pcm_plug_first(plug) ((plug)->runtime->oss.plugin_first)
36 #define snd_pcm_plug_last(plug) ((plug)->runtime->oss.plugin_last)
37 
38 /*
39  *  because some cards might have rates "very close", we ignore
40  *  all "resampling" requests within +-5%
41  */
42 static int rate_match(unsigned int src_rate, unsigned int dst_rate)
43 {
44 	unsigned int low = (src_rate * 95) / 100;
45 	unsigned int high = (src_rate * 105) / 100;
46 	return dst_rate >= low && dst_rate <= high;
47 }
48 
49 static int snd_pcm_plugin_alloc(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t frames)
50 {
51 	struct snd_pcm_plugin_format *format;
52 	ssize_t width;
53 	size_t size;
54 	unsigned int channel;
55 	struct snd_pcm_plugin_channel *c;
56 
57 	if (plugin->stream == SNDRV_PCM_STREAM_PLAYBACK) {
58 		format = &plugin->src_format;
59 	} else {
60 		format = &plugin->dst_format;
61 	}
62 	if ((width = snd_pcm_format_physical_width(format->format)) < 0)
63 		return width;
64 	size = frames * format->channels * width;
65 	snd_assert((size % 8) == 0, return -ENXIO);
66 	size /= 8;
67 	if (plugin->buf_frames < frames) {
68 		vfree(plugin->buf);
69 		plugin->buf = vmalloc(size);
70 		plugin->buf_frames = frames;
71 	}
72 	if (!plugin->buf) {
73 		plugin->buf_frames = 0;
74 		return -ENOMEM;
75 	}
76 	c = plugin->buf_channels;
77 	if (plugin->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED) {
78 		for (channel = 0; channel < format->channels; channel++, c++) {
79 			c->frames = frames;
80 			c->enabled = 1;
81 			c->wanted = 0;
82 			c->area.addr = plugin->buf;
83 			c->area.first = channel * width;
84 			c->area.step = format->channels * width;
85 		}
86 	} else if (plugin->access == SNDRV_PCM_ACCESS_RW_NONINTERLEAVED) {
87 		snd_assert((size % format->channels) == 0,);
88 		size /= format->channels;
89 		for (channel = 0; channel < format->channels; channel++, c++) {
90 			c->frames = frames;
91 			c->enabled = 1;
92 			c->wanted = 0;
93 			c->area.addr = plugin->buf + (channel * size);
94 			c->area.first = 0;
95 			c->area.step = width;
96 		}
97 	} else
98 		return -EINVAL;
99 	return 0;
100 }
101 
102 int snd_pcm_plug_alloc(struct snd_pcm_substream *plug, snd_pcm_uframes_t frames)
103 {
104 	int err;
105 	snd_assert(snd_pcm_plug_first(plug) != NULL, return -ENXIO);
106 	if (snd_pcm_plug_stream(plug) == SNDRV_PCM_STREAM_PLAYBACK) {
107 		struct snd_pcm_plugin *plugin = snd_pcm_plug_first(plug);
108 		while (plugin->next) {
109 			if (plugin->dst_frames)
110 				frames = plugin->dst_frames(plugin, frames);
111 			snd_assert(frames > 0, return -ENXIO);
112 			plugin = plugin->next;
113 			err = snd_pcm_plugin_alloc(plugin, frames);
114 			if (err < 0)
115 				return err;
116 		}
117 	} else {
118 		struct snd_pcm_plugin *plugin = snd_pcm_plug_last(plug);
119 		while (plugin->prev) {
120 			if (plugin->src_frames)
121 				frames = plugin->src_frames(plugin, frames);
122 			snd_assert(frames > 0, return -ENXIO);
123 			plugin = plugin->prev;
124 			err = snd_pcm_plugin_alloc(plugin, frames);
125 			if (err < 0)
126 				return err;
127 		}
128 	}
129 	return 0;
130 }
131 
132 
133 snd_pcm_sframes_t snd_pcm_plugin_client_channels(struct snd_pcm_plugin *plugin,
134 				       snd_pcm_uframes_t frames,
135 				       struct snd_pcm_plugin_channel **channels)
136 {
137 	*channels = plugin->buf_channels;
138 	return frames;
139 }
140 
141 int snd_pcm_plugin_build(struct snd_pcm_substream *plug,
142 			 const char *name,
143 			 struct snd_pcm_plugin_format *src_format,
144 			 struct snd_pcm_plugin_format *dst_format,
145 			 size_t extra,
146 			 struct snd_pcm_plugin **ret)
147 {
148 	struct snd_pcm_plugin *plugin;
149 	unsigned int channels;
150 
151 	snd_assert(plug != NULL, return -ENXIO);
152 	snd_assert(src_format != NULL && dst_format != NULL, return -ENXIO);
153 	plugin = kzalloc(sizeof(*plugin) + extra, GFP_KERNEL);
154 	if (plugin == NULL)
155 		return -ENOMEM;
156 	plugin->name = name;
157 	plugin->plug = plug;
158 	plugin->stream = snd_pcm_plug_stream(plug);
159 	plugin->access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
160 	plugin->src_format = *src_format;
161 	plugin->src_width = snd_pcm_format_physical_width(src_format->format);
162 	snd_assert(plugin->src_width > 0, );
163 	plugin->dst_format = *dst_format;
164 	plugin->dst_width = snd_pcm_format_physical_width(dst_format->format);
165 	snd_assert(plugin->dst_width > 0, );
166 	if (plugin->stream == SNDRV_PCM_STREAM_PLAYBACK)
167 		channels = src_format->channels;
168 	else
169 		channels = dst_format->channels;
170 	plugin->buf_channels = kcalloc(channels, sizeof(*plugin->buf_channels), GFP_KERNEL);
171 	if (plugin->buf_channels == NULL) {
172 		snd_pcm_plugin_free(plugin);
173 		return -ENOMEM;
174 	}
175 	plugin->client_channels = snd_pcm_plugin_client_channels;
176 	*ret = plugin;
177 	return 0;
178 }
179 
180 int snd_pcm_plugin_free(struct snd_pcm_plugin *plugin)
181 {
182 	if (! plugin)
183 		return 0;
184 	if (plugin->private_free)
185 		plugin->private_free(plugin);
186 	kfree(plugin->buf_channels);
187 	vfree(plugin->buf);
188 	kfree(plugin);
189 	return 0;
190 }
191 
192 snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *plug, snd_pcm_uframes_t drv_frames)
193 {
194 	struct snd_pcm_plugin *plugin, *plugin_prev, *plugin_next;
195 	int stream = snd_pcm_plug_stream(plug);
196 
197 	snd_assert(plug != NULL, return -ENXIO);
198 	if (drv_frames == 0)
199 		return 0;
200 	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
201 		plugin = snd_pcm_plug_last(plug);
202 		while (plugin && drv_frames > 0) {
203 			plugin_prev = plugin->prev;
204 			if (plugin->src_frames)
205 				drv_frames = plugin->src_frames(plugin, drv_frames);
206 			plugin = plugin_prev;
207 		}
208 	} else if (stream == SNDRV_PCM_STREAM_CAPTURE) {
209 		plugin = snd_pcm_plug_first(plug);
210 		while (plugin && drv_frames > 0) {
211 			plugin_next = plugin->next;
212 			if (plugin->dst_frames)
213 				drv_frames = plugin->dst_frames(plugin, drv_frames);
214 			plugin = plugin_next;
215 		}
216 	} else
217 		snd_BUG();
218 	return drv_frames;
219 }
220 
221 snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *plug, snd_pcm_uframes_t clt_frames)
222 {
223 	struct snd_pcm_plugin *plugin, *plugin_prev, *plugin_next;
224 	snd_pcm_sframes_t frames;
225 	int stream = snd_pcm_plug_stream(plug);
226 
227 	snd_assert(plug != NULL, return -ENXIO);
228 	if (clt_frames == 0)
229 		return 0;
230 	frames = clt_frames;
231 	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
232 		plugin = snd_pcm_plug_first(plug);
233 		while (plugin && frames > 0) {
234 			plugin_next = plugin->next;
235 			if (plugin->dst_frames) {
236 				frames = plugin->dst_frames(plugin, frames);
237 				if (frames < 0)
238 					return frames;
239 			}
240 			plugin = plugin_next;
241 		}
242 	} else if (stream == SNDRV_PCM_STREAM_CAPTURE) {
243 		plugin = snd_pcm_plug_last(plug);
244 		while (plugin) {
245 			plugin_prev = plugin->prev;
246 			if (plugin->src_frames) {
247 				frames = plugin->src_frames(plugin, frames);
248 				if (frames < 0)
249 					return frames;
250 			}
251 			plugin = plugin_prev;
252 		}
253 	} else
254 		snd_BUG();
255 	return frames;
256 }
257 
258 static int snd_pcm_plug_formats(struct snd_mask *mask, int format)
259 {
260 	struct snd_mask formats = *mask;
261 	u64 linfmts = (SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S8 |
262 		       SNDRV_PCM_FMTBIT_U16_LE | SNDRV_PCM_FMTBIT_S16_LE |
263 		       SNDRV_PCM_FMTBIT_U16_BE | SNDRV_PCM_FMTBIT_S16_BE |
264 		       SNDRV_PCM_FMTBIT_U24_LE | SNDRV_PCM_FMTBIT_S24_LE |
265 		       SNDRV_PCM_FMTBIT_U24_BE | SNDRV_PCM_FMTBIT_S24_BE |
266 		       SNDRV_PCM_FMTBIT_U24_3LE | SNDRV_PCM_FMTBIT_S24_3LE |
267 		       SNDRV_PCM_FMTBIT_U24_3BE | SNDRV_PCM_FMTBIT_S24_3BE |
268 		       SNDRV_PCM_FMTBIT_U32_LE | SNDRV_PCM_FMTBIT_S32_LE |
269 		       SNDRV_PCM_FMTBIT_U32_BE | SNDRV_PCM_FMTBIT_S32_BE);
270 	snd_mask_set(&formats, SNDRV_PCM_FORMAT_MU_LAW);
271 
272 	if (formats.bits[0] & (u32)linfmts)
273 		formats.bits[0] |= (u32)linfmts;
274 	if (formats.bits[1] & (u32)(linfmts >> 32))
275 		formats.bits[1] |= (u32)(linfmts >> 32);
276 	return snd_mask_test(&formats, format);
277 }
278 
279 static int preferred_formats[] = {
280 	SNDRV_PCM_FORMAT_S16_LE,
281 	SNDRV_PCM_FORMAT_S16_BE,
282 	SNDRV_PCM_FORMAT_U16_LE,
283 	SNDRV_PCM_FORMAT_U16_BE,
284 	SNDRV_PCM_FORMAT_S24_3LE,
285 	SNDRV_PCM_FORMAT_S24_3BE,
286 	SNDRV_PCM_FORMAT_U24_3LE,
287 	SNDRV_PCM_FORMAT_U24_3BE,
288 	SNDRV_PCM_FORMAT_S24_LE,
289 	SNDRV_PCM_FORMAT_S24_BE,
290 	SNDRV_PCM_FORMAT_U24_LE,
291 	SNDRV_PCM_FORMAT_U24_BE,
292 	SNDRV_PCM_FORMAT_S32_LE,
293 	SNDRV_PCM_FORMAT_S32_BE,
294 	SNDRV_PCM_FORMAT_U32_LE,
295 	SNDRV_PCM_FORMAT_U32_BE,
296 	SNDRV_PCM_FORMAT_S8,
297 	SNDRV_PCM_FORMAT_U8
298 };
299 
300 int snd_pcm_plug_slave_format(int format, struct snd_mask *format_mask)
301 {
302 	int i;
303 
304 	if (snd_mask_test(format_mask, format))
305 		return format;
306 	if (! snd_pcm_plug_formats(format_mask, format))
307 		return -EINVAL;
308 	if (snd_pcm_format_linear(format)) {
309 		unsigned int width = snd_pcm_format_width(format);
310 		int unsignd = snd_pcm_format_unsigned(format) > 0;
311 		int big = snd_pcm_format_big_endian(format) > 0;
312 		unsigned int badness, best = -1;
313 		int best_format = -1;
314 		for (i = 0; i < ARRAY_SIZE(preferred_formats); i++) {
315 			int f = preferred_formats[i];
316 			unsigned int w;
317 			if (!snd_mask_test(format_mask, f))
318 				continue;
319 			w = snd_pcm_format_width(f);
320 			if (w >= width)
321 				badness = w - width;
322 			else
323 				badness = width - w + 32;
324 			badness += snd_pcm_format_unsigned(f) != unsignd;
325 			badness += snd_pcm_format_big_endian(f) != big;
326 			if (badness < best) {
327 				best_format = f;
328 				best = badness;
329 			}
330 		}
331 		return best_format >= 0 ? best_format : -EINVAL;
332 	} else {
333 		switch (format) {
334 		case SNDRV_PCM_FORMAT_MU_LAW:
335 			for (i = 0; i < ARRAY_SIZE(preferred_formats); ++i) {
336 				int format1 = preferred_formats[i];
337 				if (snd_mask_test(format_mask, format1))
338 					return format1;
339 			}
340 		default:
341 			return -EINVAL;
342 		}
343 	}
344 }
345 
346 int snd_pcm_plug_format_plugins(struct snd_pcm_substream *plug,
347 				struct snd_pcm_hw_params *params,
348 				struct snd_pcm_hw_params *slave_params)
349 {
350 	struct snd_pcm_plugin_format tmpformat;
351 	struct snd_pcm_plugin_format dstformat;
352 	struct snd_pcm_plugin_format srcformat;
353 	int src_access, dst_access;
354 	struct snd_pcm_plugin *plugin = NULL;
355 	int err;
356 	int stream = snd_pcm_plug_stream(plug);
357 	int slave_interleaved = (params_channels(slave_params) == 1 ||
358 				 params_access(slave_params) == SNDRV_PCM_ACCESS_RW_INTERLEAVED);
359 
360 	switch (stream) {
361 	case SNDRV_PCM_STREAM_PLAYBACK:
362 		dstformat.format = params_format(slave_params);
363 		dstformat.rate = params_rate(slave_params);
364 		dstformat.channels = params_channels(slave_params);
365 		srcformat.format = params_format(params);
366 		srcformat.rate = params_rate(params);
367 		srcformat.channels = params_channels(params);
368 		src_access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
369 		dst_access = (slave_interleaved ? SNDRV_PCM_ACCESS_RW_INTERLEAVED :
370 						  SNDRV_PCM_ACCESS_RW_NONINTERLEAVED);
371 		break;
372 	case SNDRV_PCM_STREAM_CAPTURE:
373 		dstformat.format = params_format(params);
374 		dstformat.rate = params_rate(params);
375 		dstformat.channels = params_channels(params);
376 		srcformat.format = params_format(slave_params);
377 		srcformat.rate = params_rate(slave_params);
378 		srcformat.channels = params_channels(slave_params);
379 		src_access = (slave_interleaved ? SNDRV_PCM_ACCESS_RW_INTERLEAVED :
380 						  SNDRV_PCM_ACCESS_RW_NONINTERLEAVED);
381 		dst_access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
382 		break;
383 	default:
384 		snd_BUG();
385 		return -EINVAL;
386 	}
387 	tmpformat = srcformat;
388 
389 	pdprintf("srcformat: format=%i, rate=%i, channels=%i\n",
390 		 srcformat.format,
391 		 srcformat.rate,
392 		 srcformat.channels);
393 	pdprintf("dstformat: format=%i, rate=%i, channels=%i\n",
394 		 dstformat.format,
395 		 dstformat.rate,
396 		 dstformat.channels);
397 
398 	/* Format change (linearization) */
399 	if (! rate_match(srcformat.rate, dstformat.rate) &&
400 	    ! snd_pcm_format_linear(srcformat.format)) {
401 		if (srcformat.format != SNDRV_PCM_FORMAT_MU_LAW)
402 			return -EINVAL;
403 		tmpformat.format = SNDRV_PCM_FORMAT_S16;
404 		err = snd_pcm_plugin_build_mulaw(plug,
405 						 &srcformat, &tmpformat,
406 						 &plugin);
407 		if (err < 0)
408 			return err;
409 		err = snd_pcm_plugin_append(plugin);
410 		if (err < 0) {
411 			snd_pcm_plugin_free(plugin);
412 			return err;
413 		}
414 		srcformat = tmpformat;
415 		src_access = dst_access;
416 	}
417 
418 	/* channels reduction */
419 	if (srcformat.channels > dstformat.channels) {
420 		tmpformat.channels = dstformat.channels;
421 		err = snd_pcm_plugin_build_route(plug, &srcformat, &tmpformat, &plugin);
422 		pdprintf("channels reduction: src=%i, dst=%i returns %i\n", srcformat.channels, tmpformat.channels, err);
423 		if (err < 0)
424 			return err;
425 		err = snd_pcm_plugin_append(plugin);
426 		if (err < 0) {
427 			snd_pcm_plugin_free(plugin);
428 			return err;
429 		}
430 		srcformat = tmpformat;
431 		src_access = dst_access;
432 	}
433 
434 	/* rate resampling */
435 	if (!rate_match(srcformat.rate, dstformat.rate)) {
436 		if (srcformat.format != SNDRV_PCM_FORMAT_S16) {
437 			/* convert to S16 for resampling */
438 			tmpformat.format = SNDRV_PCM_FORMAT_S16;
439 			err = snd_pcm_plugin_build_linear(plug,
440 							  &srcformat, &tmpformat,
441 							  &plugin);
442 			if (err < 0)
443 				return err;
444 			err = snd_pcm_plugin_append(plugin);
445 			if (err < 0) {
446 				snd_pcm_plugin_free(plugin);
447 				return err;
448 			}
449 			srcformat = tmpformat;
450 			src_access = dst_access;
451 		}
452 		tmpformat.rate = dstformat.rate;
453         	err = snd_pcm_plugin_build_rate(plug,
454         					&srcformat, &tmpformat,
455 						&plugin);
456 		pdprintf("rate down resampling: src=%i, dst=%i returns %i\n", srcformat.rate, tmpformat.rate, err);
457 		if (err < 0)
458 			return err;
459 		err = snd_pcm_plugin_append(plugin);
460 		if (err < 0) {
461 			snd_pcm_plugin_free(plugin);
462 			return err;
463 		}
464 		srcformat = tmpformat;
465 		src_access = dst_access;
466         }
467 
468 	/* format change */
469 	if (srcformat.format != dstformat.format) {
470 		tmpformat.format = dstformat.format;
471 		if (srcformat.format == SNDRV_PCM_FORMAT_MU_LAW ||
472 		    tmpformat.format == SNDRV_PCM_FORMAT_MU_LAW) {
473 			err = snd_pcm_plugin_build_mulaw(plug,
474 							 &srcformat, &tmpformat,
475 							 &plugin);
476 		}
477 		else if (snd_pcm_format_linear(srcformat.format) &&
478 			 snd_pcm_format_linear(tmpformat.format)) {
479 			err = snd_pcm_plugin_build_linear(plug,
480 							  &srcformat, &tmpformat,
481 							  &plugin);
482 		}
483 		else
484 			return -EINVAL;
485 		pdprintf("format change: src=%i, dst=%i returns %i\n", srcformat.format, tmpformat.format, err);
486 		if (err < 0)
487 			return err;
488 		err = snd_pcm_plugin_append(plugin);
489 		if (err < 0) {
490 			snd_pcm_plugin_free(plugin);
491 			return err;
492 		}
493 		srcformat = tmpformat;
494 		src_access = dst_access;
495 	}
496 
497 	/* channels extension */
498 	if (srcformat.channels < dstformat.channels) {
499 		tmpformat.channels = dstformat.channels;
500 		err = snd_pcm_plugin_build_route(plug, &srcformat, &tmpformat, &plugin);
501 		pdprintf("channels extension: src=%i, dst=%i returns %i\n", srcformat.channels, tmpformat.channels, err);
502 		if (err < 0)
503 			return err;
504 		err = snd_pcm_plugin_append(plugin);
505 		if (err < 0) {
506 			snd_pcm_plugin_free(plugin);
507 			return err;
508 		}
509 		srcformat = tmpformat;
510 		src_access = dst_access;
511 	}
512 
513 	/* de-interleave */
514 	if (src_access != dst_access) {
515 		err = snd_pcm_plugin_build_copy(plug,
516 						&srcformat,
517 						&tmpformat,
518 						&plugin);
519 		pdprintf("interleave change (copy: returns %i)\n", err);
520 		if (err < 0)
521 			return err;
522 		err = snd_pcm_plugin_append(plugin);
523 		if (err < 0) {
524 			snd_pcm_plugin_free(plugin);
525 			return err;
526 		}
527 	}
528 
529 	return 0;
530 }
531 
532 snd_pcm_sframes_t snd_pcm_plug_client_channels_buf(struct snd_pcm_substream *plug,
533 					 char *buf,
534 					 snd_pcm_uframes_t count,
535 					 struct snd_pcm_plugin_channel **channels)
536 {
537 	struct snd_pcm_plugin *plugin;
538 	struct snd_pcm_plugin_channel *v;
539 	struct snd_pcm_plugin_format *format;
540 	int width, nchannels, channel;
541 	int stream = snd_pcm_plug_stream(plug);
542 
543 	snd_assert(buf != NULL, return -ENXIO);
544 	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
545 		plugin = snd_pcm_plug_first(plug);
546 		format = &plugin->src_format;
547 	} else {
548 		plugin = snd_pcm_plug_last(plug);
549 		format = &plugin->dst_format;
550 	}
551 	v = plugin->buf_channels;
552 	*channels = v;
553 	if ((width = snd_pcm_format_physical_width(format->format)) < 0)
554 		return width;
555 	nchannels = format->channels;
556 	snd_assert(plugin->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED || format->channels <= 1, return -ENXIO);
557 	for (channel = 0; channel < nchannels; channel++, v++) {
558 		v->frames = count;
559 		v->enabled = 1;
560 		v->wanted = (stream == SNDRV_PCM_STREAM_CAPTURE);
561 		v->area.addr = buf;
562 		v->area.first = channel * width;
563 		v->area.step = nchannels * width;
564 	}
565 	return count;
566 }
567 
568 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)
569 {
570 	struct snd_pcm_plugin *plugin, *next;
571 	struct snd_pcm_plugin_channel *dst_channels;
572 	int err;
573 	snd_pcm_sframes_t frames = size;
574 
575 	plugin = snd_pcm_plug_first(plug);
576 	while (plugin && frames > 0) {
577 		if ((next = plugin->next) != NULL) {
578 			snd_pcm_sframes_t frames1 = frames;
579 			if (plugin->dst_frames)
580 				frames1 = plugin->dst_frames(plugin, frames);
581 			if ((err = next->client_channels(next, frames1, &dst_channels)) < 0) {
582 				return err;
583 			}
584 			if (err != frames1) {
585 				frames = err;
586 				if (plugin->src_frames)
587 					frames = plugin->src_frames(plugin, frames1);
588 			}
589 		} else
590 			dst_channels = NULL;
591 		pdprintf("write plugin: %s, %li\n", plugin->name, frames);
592 		if ((frames = plugin->transfer(plugin, src_channels, dst_channels, frames)) < 0)
593 			return frames;
594 		src_channels = dst_channels;
595 		plugin = next;
596 	}
597 	return snd_pcm_plug_client_size(plug, frames);
598 }
599 
600 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)
601 {
602 	struct snd_pcm_plugin *plugin, *next;
603 	struct snd_pcm_plugin_channel *src_channels, *dst_channels;
604 	snd_pcm_sframes_t frames = size;
605 	int err;
606 
607 	frames = snd_pcm_plug_slave_size(plug, frames);
608 	if (frames < 0)
609 		return frames;
610 
611 	src_channels = NULL;
612 	plugin = snd_pcm_plug_first(plug);
613 	while (plugin && frames > 0) {
614 		if ((next = plugin->next) != NULL) {
615 			if ((err = plugin->client_channels(plugin, frames, &dst_channels)) < 0) {
616 				return err;
617 			}
618 			frames = err;
619 		} else {
620 			dst_channels = dst_channels_final;
621 		}
622 		pdprintf("read plugin: %s, %li\n", plugin->name, frames);
623 		if ((frames = plugin->transfer(plugin, src_channels, dst_channels, frames)) < 0)
624 			return frames;
625 		plugin = next;
626 		src_channels = dst_channels;
627 	}
628 	return frames;
629 }
630 
631 int snd_pcm_area_silence(const struct snd_pcm_channel_area *dst_area, size_t dst_offset,
632 			 size_t samples, int format)
633 {
634 	/* FIXME: sub byte resolution and odd dst_offset */
635 	unsigned char *dst;
636 	unsigned int dst_step;
637 	int width;
638 	const unsigned char *silence;
639 	if (!dst_area->addr)
640 		return 0;
641 	dst = dst_area->addr + (dst_area->first + dst_area->step * dst_offset) / 8;
642 	width = snd_pcm_format_physical_width(format);
643 	if (width <= 0)
644 		return -EINVAL;
645 	if (dst_area->step == (unsigned int) width && width >= 8)
646 		return snd_pcm_format_set_silence(format, dst, samples);
647 	silence = snd_pcm_format_silence_64(format);
648 	if (! silence)
649 		return -EINVAL;
650 	dst_step = dst_area->step / 8;
651 	if (width == 4) {
652 		/* Ima ADPCM */
653 		int dstbit = dst_area->first % 8;
654 		int dstbit_step = dst_area->step % 8;
655 		while (samples-- > 0) {
656 			if (dstbit)
657 				*dst &= 0xf0;
658 			else
659 				*dst &= 0x0f;
660 			dst += dst_step;
661 			dstbit += dstbit_step;
662 			if (dstbit == 8) {
663 				dst++;
664 				dstbit = 0;
665 			}
666 		}
667 	} else {
668 		width /= 8;
669 		while (samples-- > 0) {
670 			memcpy(dst, silence, width);
671 			dst += dst_step;
672 		}
673 	}
674 	return 0;
675 }
676 
677 int snd_pcm_area_copy(const struct snd_pcm_channel_area *src_area, size_t src_offset,
678 		      const struct snd_pcm_channel_area *dst_area, size_t dst_offset,
679 		      size_t samples, int format)
680 {
681 	/* FIXME: sub byte resolution and odd dst_offset */
682 	char *src, *dst;
683 	int width;
684 	int src_step, dst_step;
685 	src = src_area->addr + (src_area->first + src_area->step * src_offset) / 8;
686 	if (!src_area->addr)
687 		return snd_pcm_area_silence(dst_area, dst_offset, samples, format);
688 	dst = dst_area->addr + (dst_area->first + dst_area->step * dst_offset) / 8;
689 	if (!dst_area->addr)
690 		return 0;
691 	width = snd_pcm_format_physical_width(format);
692 	if (width <= 0)
693 		return -EINVAL;
694 	if (src_area->step == (unsigned int) width &&
695 	    dst_area->step == (unsigned int) width && width >= 8) {
696 		size_t bytes = samples * width / 8;
697 		memcpy(dst, src, bytes);
698 		return 0;
699 	}
700 	src_step = src_area->step / 8;
701 	dst_step = dst_area->step / 8;
702 	if (width == 4) {
703 		/* Ima ADPCM */
704 		int srcbit = src_area->first % 8;
705 		int srcbit_step = src_area->step % 8;
706 		int dstbit = dst_area->first % 8;
707 		int dstbit_step = dst_area->step % 8;
708 		while (samples-- > 0) {
709 			unsigned char srcval;
710 			if (srcbit)
711 				srcval = *src & 0x0f;
712 			else
713 				srcval = (*src & 0xf0) >> 4;
714 			if (dstbit)
715 				*dst = (*dst & 0xf0) | srcval;
716 			else
717 				*dst = (*dst & 0x0f) | (srcval << 4);
718 			src += src_step;
719 			srcbit += srcbit_step;
720 			if (srcbit == 8) {
721 				src++;
722 				srcbit = 0;
723 			}
724 			dst += dst_step;
725 			dstbit += dstbit_step;
726 			if (dstbit == 8) {
727 				dst++;
728 				dstbit = 0;
729 			}
730 		}
731 	} else {
732 		width /= 8;
733 		while (samples-- > 0) {
734 			memcpy(dst, src, width);
735 			src += src_step;
736 			dst += dst_step;
737 		}
738 	}
739 	return 0;
740 }
741