xref: /freebsd/sys/dev/sound/pcm/buffer.c (revision 94942af266ac119ede0ca836f9aa5a5ac0582938)
1 /*-
2  * Copyright (c) 1999 Cameron Grant <cg@freebsd.org>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  */
26 
27 #include <dev/sound/pcm/sound.h>
28 
29 #include "feeder_if.h"
30 
31 SND_DECLARE_FILE("$FreeBSD$");
32 
33 struct snd_dbuf *
34 sndbuf_create(device_t dev, char *drv, char *desc, struct pcm_channel *channel)
35 {
36 	struct snd_dbuf *b;
37 
38 	b = malloc(sizeof(*b), M_DEVBUF, M_WAITOK | M_ZERO);
39 	snprintf(b->name, SNDBUF_NAMELEN, "%s:%s", drv, desc);
40 	b->dev = dev;
41 	b->channel = channel;
42 
43 	return b;
44 }
45 
46 void
47 sndbuf_destroy(struct snd_dbuf *b)
48 {
49 	sndbuf_free(b);
50 	free(b, M_DEVBUF);
51 }
52 
53 bus_addr_t
54 sndbuf_getbufaddr(struct snd_dbuf *buf)
55 {
56 	return (buf->buf_addr);
57 }
58 
59 static void
60 sndbuf_setmap(void *arg, bus_dma_segment_t *segs, int nseg, int error)
61 {
62 	struct snd_dbuf *b = (struct snd_dbuf *)arg;
63 
64 	if (bootverbose) {
65 		device_printf(b->dev, "sndbuf_setmap %lx, %lx; ",
66 		    (u_long)segs[0].ds_addr, (u_long)segs[0].ds_len);
67 		printf("%p -> %lx\n", b->buf, (u_long)segs[0].ds_addr);
68 	}
69 	if (error == 0)
70 		b->buf_addr = segs[0].ds_addr;
71 	else
72 		b->buf_addr = 0;
73 }
74 
75 /*
76  * Allocate memory for DMA buffer. If the device does not use DMA transfers,
77  * the driver can call malloc(9) and sndbuf_setup() itself.
78  */
79 
80 int
81 sndbuf_alloc(struct snd_dbuf *b, bus_dma_tag_t dmatag, int dmaflags,
82     unsigned int size)
83 {
84 	int ret;
85 
86 	b->dmatag = dmatag;
87 	b->dmaflags = dmaflags | BUS_DMA_NOWAIT;
88 	b->maxsize = size;
89 	b->bufsize = b->maxsize;
90 	b->buf_addr = 0;
91 	b->flags |= SNDBUF_F_MANAGED;
92 	if (bus_dmamem_alloc(b->dmatag, (void **)&b->buf, b->dmaflags,
93 	    &b->dmamap)) {
94 		sndbuf_free(b);
95 		return (ENOMEM);
96 	}
97 	if (bus_dmamap_load(b->dmatag, b->dmamap, b->buf, b->maxsize,
98 	    sndbuf_setmap, b, 0) != 0 || b->buf_addr == 0) {
99 		sndbuf_free(b);
100 		return (ENOMEM);
101 	}
102 
103 	ret = sndbuf_resize(b, 2, b->maxsize / 2);
104 	if (ret != 0)
105 		sndbuf_free(b);
106 
107 	return (ret);
108 }
109 
110 int
111 sndbuf_setup(struct snd_dbuf *b, void *buf, unsigned int size)
112 {
113 	b->flags &= ~SNDBUF_F_MANAGED;
114 	if (buf)
115 		b->flags |= SNDBUF_F_MANAGED;
116 	b->buf = buf;
117 	b->maxsize = size;
118 	b->bufsize = b->maxsize;
119 	return sndbuf_resize(b, 2, b->maxsize / 2);
120 }
121 
122 void
123 sndbuf_free(struct snd_dbuf *b)
124 {
125 	if (b->tmpbuf)
126 		free(b->tmpbuf, M_DEVBUF);
127 
128 	if (b->shadbuf)
129 		free(b->shadbuf, M_DEVBUF);
130 
131 	if (b->buf) {
132 		if (b->flags & SNDBUF_F_MANAGED) {
133 			if (b->dmamap)
134 				bus_dmamap_unload(b->dmatag, b->dmamap);
135 			if (b->dmatag)
136 				bus_dmamem_free(b->dmatag, b->buf, b->dmamap);
137 		} else
138 			free(b->buf, M_DEVBUF);
139 	}
140 
141 	b->tmpbuf = NULL;
142 	b->shadbuf = NULL;
143 	b->buf = NULL;
144 	b->sl = 0;
145 	b->dmatag = NULL;
146 	b->dmamap = NULL;
147 }
148 
149 int
150 sndbuf_resize(struct snd_dbuf *b, unsigned int blkcnt, unsigned int blksz)
151 {
152 	u_int8_t *tmpbuf, *f2;
153 
154 	chn_lock(b->channel);
155 	if (b->maxsize == 0)
156 		goto out;
157 	if (blkcnt == 0)
158 		blkcnt = b->blkcnt;
159 	if (blksz == 0)
160 		blksz = b->blksz;
161 	if (blkcnt < 2 || blksz < 16 || (blkcnt * blksz > b->maxsize)) {
162 		chn_unlock(b->channel);
163 		return EINVAL;
164 	}
165 	if (blkcnt == b->blkcnt && blksz == b->blksz)
166 		goto out;
167 
168 	chn_unlock(b->channel);
169 	tmpbuf = malloc(blkcnt * blksz, M_DEVBUF, M_NOWAIT);
170 	if (tmpbuf == NULL)
171 		return ENOMEM;
172 	chn_lock(b->channel);
173 	b->blkcnt = blkcnt;
174 	b->blksz = blksz;
175 	b->bufsize = blkcnt * blksz;
176 	f2 =  b->tmpbuf;
177 	b->tmpbuf = tmpbuf;
178 	sndbuf_reset(b);
179 	chn_unlock(b->channel);
180 	free(f2, M_DEVBUF);
181 	return 0;
182 out:
183 	chn_unlock(b->channel);
184 	return 0;
185 }
186 
187 int
188 sndbuf_remalloc(struct snd_dbuf *b, unsigned int blkcnt, unsigned int blksz)
189 {
190         u_int8_t *buf, *tmpbuf, *f1, *f2;
191 	u_int8_t *shadbuf, *f3;
192         unsigned int bufsize;
193 	int ret;
194 
195 	if (blkcnt < 2 || blksz < 16)
196 		return EINVAL;
197 
198 	bufsize = blksz * blkcnt;
199 
200 	chn_unlock(b->channel);
201 	buf = malloc(bufsize, M_DEVBUF, M_WAITOK);
202 	tmpbuf = malloc(bufsize, M_DEVBUF, M_WAITOK);
203 	shadbuf = malloc(bufsize, M_DEVBUF, M_WAITOK);
204 
205 	chn_lock(b->channel);
206 
207 	b->blkcnt = blkcnt;
208 	b->blksz = blksz;
209 	b->bufsize = bufsize;
210 	b->maxsize = bufsize;
211 	f1 = b->buf;
212 	f2 = b->tmpbuf;
213 	b->buf = buf;
214 	b->tmpbuf = tmpbuf;
215 	f3 = b->shadbuf;
216 	b->shadbuf = shadbuf;
217 	b->sl = bufsize;
218 
219 	sndbuf_reset(b);
220 
221 	chn_unlock(b->channel);
222       	if (f1)
223 		free(f1, M_DEVBUF);
224       	if (f2)
225 		free(f2, M_DEVBUF);
226 	if (f3)
227 		free(f3, M_DEVBUF);
228 
229 	ret = 0;
230 
231 	chn_lock(b->channel);
232 	return ret;
233 }
234 
235 /**
236  * @brief Zero out space in buffer free area
237  *
238  * This function clears a chunk of @c length bytes in the buffer free area
239  * (i.e., where the next write will be placed).
240  *
241  * @param b		buffer context
242  * @param length	number of bytes to blank
243  */
244 void
245 sndbuf_clear(struct snd_dbuf *b, unsigned int length)
246 {
247 	int i;
248 	u_char data, *p;
249 
250 	if (length == 0)
251 		return;
252 	if (length > b->bufsize)
253 		length = b->bufsize;
254 
255 	data = sndbuf_zerodata(b->fmt);
256 
257 	i = sndbuf_getfreeptr(b);
258 	p = sndbuf_getbuf(b);
259 	while (length > 0) {
260 		p[i] = data;
261 		length--;
262 		i++;
263 		if (i >= b->bufsize)
264 			i = 0;
265 	}
266 }
267 
268 /**
269  * @brief Zap buffer contents, resetting "ready area" fields
270  *
271  * @param b	buffer context
272  */
273 void
274 sndbuf_fillsilence(struct snd_dbuf *b)
275 {
276 	if (b->bufsize > 0)
277 		memset(sndbuf_getbuf(b), sndbuf_zerodata(b->fmt), b->bufsize);
278 	b->rp = 0;
279 	b->rl = b->bufsize;
280 }
281 
282 /**
283  * @brief Reset buffer w/o flushing statistics
284  *
285  * This function just zeroes out buffer contents and sets the "ready length"
286  * to zero.  This was originally to facilitate minimal playback interruption
287  * (i.e., dropped samples) in SNDCTL_DSP_SILENCE/SKIP ioctls.
288  *
289  * @param b	buffer context
290  */
291 void
292 sndbuf_softreset(struct snd_dbuf *b)
293 {
294 	b->rl = 0;
295 	if (b->buf && b->bufsize > 0)
296 		sndbuf_clear(b, b->bufsize);
297 }
298 
299 void
300 sndbuf_reset(struct snd_dbuf *b)
301 {
302 	b->hp = 0;
303 	b->rp = 0;
304 	b->rl = 0;
305 	b->dl = 0;
306 	b->prev_total = 0;
307 	b->total = 0;
308 	b->xrun = 0;
309 	if (b->buf && b->bufsize > 0)
310 		sndbuf_clear(b, b->bufsize);
311 	sndbuf_clearshadow(b);
312 }
313 
314 u_int32_t
315 sndbuf_getfmt(struct snd_dbuf *b)
316 {
317 	return b->fmt;
318 }
319 
320 int
321 sndbuf_setfmt(struct snd_dbuf *b, u_int32_t fmt)
322 {
323 	b->fmt = fmt;
324 	b->bps = 1;
325 	b->bps <<= (b->fmt & AFMT_STEREO)? 1 : 0;
326 	if (b->fmt & AFMT_16BIT)
327 		b->bps <<= 1;
328 	else if (b->fmt & AFMT_24BIT)
329 		b->bps *= 3;
330 	else if (b->fmt & AFMT_32BIT)
331 		b->bps <<= 2;
332 	return 0;
333 }
334 
335 unsigned int
336 sndbuf_getspd(struct snd_dbuf *b)
337 {
338 	return b->spd;
339 }
340 
341 void
342 sndbuf_setspd(struct snd_dbuf *b, unsigned int spd)
343 {
344 	b->spd = spd;
345 }
346 
347 unsigned int
348 sndbuf_getalign(struct snd_dbuf *b)
349 {
350 	static int align[] = {0, 1, 1, 2, 2, 2, 2, 3};
351 
352 	return align[b->bps - 1];
353 }
354 
355 unsigned int
356 sndbuf_getblkcnt(struct snd_dbuf *b)
357 {
358 	return b->blkcnt;
359 }
360 
361 void
362 sndbuf_setblkcnt(struct snd_dbuf *b, unsigned int blkcnt)
363 {
364 	b->blkcnt = blkcnt;
365 }
366 
367 unsigned int
368 sndbuf_getblksz(struct snd_dbuf *b)
369 {
370 	return b->blksz;
371 }
372 
373 void
374 sndbuf_setblksz(struct snd_dbuf *b, unsigned int blksz)
375 {
376 	b->blksz = blksz;
377 }
378 
379 unsigned int
380 sndbuf_getbps(struct snd_dbuf *b)
381 {
382 	return b->bps;
383 }
384 
385 void *
386 sndbuf_getbuf(struct snd_dbuf *b)
387 {
388 	return b->buf;
389 }
390 
391 void *
392 sndbuf_getbufofs(struct snd_dbuf *b, unsigned int ofs)
393 {
394 	KASSERT(ofs < b->bufsize, ("%s: ofs invalid %d", __func__, ofs));
395 
396 	return b->buf + ofs;
397 }
398 
399 unsigned int
400 sndbuf_getsize(struct snd_dbuf *b)
401 {
402 	return b->bufsize;
403 }
404 
405 unsigned int
406 sndbuf_getmaxsize(struct snd_dbuf *b)
407 {
408 	return b->maxsize;
409 }
410 
411 unsigned int
412 sndbuf_runsz(struct snd_dbuf *b)
413 {
414 	return b->dl;
415 }
416 
417 void
418 sndbuf_setrun(struct snd_dbuf *b, int go)
419 {
420 	b->dl = go? b->blksz : 0;
421 }
422 
423 struct selinfo *
424 sndbuf_getsel(struct snd_dbuf *b)
425 {
426 	return &b->sel;
427 }
428 
429 /************************************************************/
430 unsigned int
431 sndbuf_getxrun(struct snd_dbuf *b)
432 {
433 	SNDBUF_LOCKASSERT(b);
434 
435 	return b->xrun;
436 }
437 
438 void
439 sndbuf_setxrun(struct snd_dbuf *b, unsigned int xrun)
440 {
441 	SNDBUF_LOCKASSERT(b);
442 
443 	b->xrun = xrun;
444 }
445 
446 unsigned int
447 sndbuf_gethwptr(struct snd_dbuf *b)
448 {
449 	SNDBUF_LOCKASSERT(b);
450 
451 	return b->hp;
452 }
453 
454 void
455 sndbuf_sethwptr(struct snd_dbuf *b, unsigned int ptr)
456 {
457 	SNDBUF_LOCKASSERT(b);
458 
459 	b->hp = ptr;
460 }
461 
462 unsigned int
463 sndbuf_getready(struct snd_dbuf *b)
464 {
465 	SNDBUF_LOCKASSERT(b);
466 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
467 
468 	return b->rl;
469 }
470 
471 unsigned int
472 sndbuf_getreadyptr(struct snd_dbuf *b)
473 {
474 	SNDBUF_LOCKASSERT(b);
475 	KASSERT((b->rp >= 0) && (b->rp <= b->bufsize), ("%s: b->rp invalid %d", __func__, b->rp));
476 
477 	return b->rp;
478 }
479 
480 unsigned int
481 sndbuf_getfree(struct snd_dbuf *b)
482 {
483 	SNDBUF_LOCKASSERT(b);
484 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
485 
486 	return b->bufsize - b->rl;
487 }
488 
489 unsigned int
490 sndbuf_getfreeptr(struct snd_dbuf *b)
491 {
492 	SNDBUF_LOCKASSERT(b);
493 	KASSERT((b->rp >= 0) && (b->rp <= b->bufsize), ("%s: b->rp invalid %d", __func__, b->rp));
494 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
495 
496 	return (b->rp + b->rl) % b->bufsize;
497 }
498 
499 unsigned int
500 sndbuf_getblocks(struct snd_dbuf *b)
501 {
502 	SNDBUF_LOCKASSERT(b);
503 
504 	return b->total / b->blksz;
505 }
506 
507 unsigned int
508 sndbuf_getprevblocks(struct snd_dbuf *b)
509 {
510 	SNDBUF_LOCKASSERT(b);
511 
512 	return b->prev_total / b->blksz;
513 }
514 
515 unsigned int
516 sndbuf_gettotal(struct snd_dbuf *b)
517 {
518 	SNDBUF_LOCKASSERT(b);
519 
520 	return b->total;
521 }
522 
523 void
524 sndbuf_updateprevtotal(struct snd_dbuf *b)
525 {
526 	SNDBUF_LOCKASSERT(b);
527 
528 	b->prev_total = b->total;
529 }
530 
531 unsigned int
532 snd_xbytes(unsigned int v, unsigned int from, unsigned int to)
533 {
534 	unsigned int w, x, y;
535 
536 	if (from == to)
537 		return v;
538 
539 	if (from == 0 || to == 0 || v == 0)
540 		return 0;
541 
542 	x = from;
543 	y = to;
544 	while (y != 0) {
545 		w = x % y;
546 		x = y;
547 		y = w;
548 	}
549 	from /= x;
550 	to /= x;
551 
552 	return (unsigned int)(((u_int64_t)v * to) / from);
553 }
554 
555 unsigned int
556 sndbuf_xbytes(unsigned int v, struct snd_dbuf *from, struct snd_dbuf *to)
557 {
558 	if (from == NULL || to == NULL || v == 0)
559 		return 0;
560 
561 	return snd_xbytes(v, sndbuf_getbps(from) * sndbuf_getspd(from),
562 	    sndbuf_getbps(to) * sndbuf_getspd(to));
563 }
564 
565 u_int8_t
566 sndbuf_zerodata(u_int32_t fmt)
567 {
568 	if (fmt & AFMT_SIGNED)
569 		return (0x00);
570 	else if (fmt & AFMT_MU_LAW)
571 		return (0x7f);
572 	else if (fmt & AFMT_A_LAW)
573 		return (0x55);
574 	return (0x80);
575 }
576 
577 /************************************************************/
578 
579 /**
580  * @brief Acquire buffer space to extend ready area
581  *
582  * This function extends the ready area length by @c count bytes, and may
583  * optionally copy samples from another location stored in @c from.  The
584  * counter @c snd_dbuf::total is also incremented by @c count bytes.
585  *
586  * @param b	audio buffer
587  * @param from	sample source (optional)
588  * @param count	number of bytes to acquire
589  *
590  * @retval 0	Unconditional
591  */
592 int
593 sndbuf_acquire(struct snd_dbuf *b, u_int8_t *from, unsigned int count)
594 {
595 	int l;
596 
597 	KASSERT(count <= sndbuf_getfree(b), ("%s: count %d > free %d", __func__, count, sndbuf_getfree(b)));
598 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
599 	b->total += count;
600 	if (from != NULL) {
601 		while (count > 0) {
602 			l = min(count, sndbuf_getsize(b) - sndbuf_getfreeptr(b));
603 			bcopy(from, sndbuf_getbufofs(b, sndbuf_getfreeptr(b)), l);
604 			from += l;
605 			b->rl += l;
606 			count -= l;
607 		}
608 	} else
609 		b->rl += count;
610 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d, count %d", __func__, b->rl, count));
611 
612 	return 0;
613 }
614 
615 /**
616  * @brief Dispose samples from channel buffer, increasing size of ready area
617  *
618  * This function discards samples from the supplied buffer by advancing the
619  * ready area start pointer and decrementing the ready area length.  If
620  * @c to is not NULL, then the discard samples will be copied to the location
621  * it points to.
622  *
623  * @param b	PCM channel sound buffer
624  * @param to	destination buffer (optional)
625  * @param count	number of bytes to discard
626  *
627  * @returns 0 unconditionally
628  */
629 int
630 sndbuf_dispose(struct snd_dbuf *b, u_int8_t *to, unsigned int count)
631 {
632 	int l;
633 
634 	KASSERT(count <= sndbuf_getready(b), ("%s: count %d > ready %d", __func__, count, sndbuf_getready(b)));
635 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
636 	if (to != NULL) {
637 		while (count > 0) {
638 			l = min(count, sndbuf_getsize(b) - sndbuf_getreadyptr(b));
639 			bcopy(sndbuf_getbufofs(b, sndbuf_getreadyptr(b)), to, l);
640 			to += l;
641 			b->rl -= l;
642 			b->rp = (b->rp + l) % b->bufsize;
643 			count -= l;
644 		}
645 	} else {
646 		b->rl -= count;
647 		b->rp = (b->rp + count) % b->bufsize;
648 	}
649 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d, count %d", __func__, b->rl, count));
650 
651 	return 0;
652 }
653 
654 /* count is number of bytes we want added to destination buffer */
655 int
656 sndbuf_feed(struct snd_dbuf *from, struct snd_dbuf *to, struct pcm_channel *channel, struct pcm_feeder *feeder, unsigned int count)
657 {
658 	unsigned int cnt;
659 
660 	KASSERT(count > 0, ("can't feed 0 bytes"));
661 
662 	if (sndbuf_getfree(to) < count)
663 		return EINVAL;
664 
665 	do {
666 		cnt = FEEDER_FEED(feeder, channel, to->tmpbuf, count, from);
667 		if (cnt)
668 			sndbuf_acquire(to, to->tmpbuf, cnt);
669 		/* the root feeder has called sndbuf_dispose(from, , bytes fetched) */
670 		count -= cnt;
671 	} while (count && cnt);
672 
673 	return 0;
674 }
675 
676 /************************************************************/
677 
678 void
679 sndbuf_dump(struct snd_dbuf *b, char *s, u_int32_t what)
680 {
681 	printf("%s: [", s);
682 	if (what & 0x01)
683 		printf(" bufsize: %d, maxsize: %d", b->bufsize, b->maxsize);
684 	if (what & 0x02)
685 		printf(" dl: %d, rp: %d, rl: %d, hp: %d", b->dl, b->rp, b->rl, b->hp);
686 	if (what & 0x04)
687 		printf(" total: %d, prev_total: %d, xrun: %d", b->total, b->prev_total, b->xrun);
688    	if (what & 0x08)
689 		printf(" fmt: 0x%x, spd: %d", b->fmt, b->spd);
690 	if (what & 0x10)
691 		printf(" blksz: %d, blkcnt: %d, flags: 0x%x", b->blksz, b->blkcnt, b->flags);
692 	printf(" ]\n");
693 }
694 
695 /************************************************************/
696 u_int32_t
697 sndbuf_getflags(struct snd_dbuf *b)
698 {
699 	return b->flags;
700 }
701 
702 void
703 sndbuf_setflags(struct snd_dbuf *b, u_int32_t flags, int on)
704 {
705 	b->flags &= ~flags;
706 	if (on)
707 		b->flags |= flags;
708 }
709 
710 /**
711  * @brief Clear the shadow buffer by filling with samples equal to zero.
712  *
713  * @param b buffer to clear
714  */
715 void
716 sndbuf_clearshadow(struct snd_dbuf *b)
717 {
718 	KASSERT(b != NULL, ("b is a null pointer"));
719 	KASSERT(b->sl >= 0, ("illegal shadow length"));
720 
721 	if ((b->shadbuf != NULL) && (b->sl > 0))
722 		memset(b->shadbuf, sndbuf_zerodata(b->fmt), b->sl);
723 }
724 
725 #ifdef OSSV4_EXPERIMENT
726 /**
727  * @brief Return peak value from samples in buffer ready area.
728  *
729  * Peak ranges from 0-32767.  If channel is monaural, most significant 16
730  * bits will be zero.  For now, only expects to work with 1-2 channel
731  * buffers.
732  *
733  * @note  Currently only operates with linear PCM formats.
734  *
735  * @param b buffer to analyze
736  * @param lpeak pointer to store left peak value
737  * @param rpeak pointer to store right peak value
738  */
739 void
740 sndbuf_getpeaks(struct snd_dbuf *b, int *lp, int *rp)
741 {
742 	u_int32_t lpeak, rpeak;
743 
744 	lpeak = 0;
745 	rpeak = 0;
746 
747 	/**
748 	 * @todo fill this in later
749 	 */
750 }
751 #endif
752