xref: /freebsd-13.1/sys/dev/sound/pcm/buffer.c (revision 4dfcb057)
1 /*-
2  * Copyright (c) 1999 Cameron Grant <[email protected]>
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 	if (b->tmpbuf)
50 		free(b->tmpbuf, M_DEVBUF);
51 	if (b->shadbuf)
52 		free(b->shadbuf, M_DEVBUF);
53 	if (!(b->flags & SNDBUF_F_MANAGED) && b->buf)
54 		free(b->buf, M_DEVBUF);
55 	free(b, M_DEVBUF);
56 }
57 
58 bus_addr_t
59 sndbuf_getbufaddr(struct snd_dbuf *buf)
60 {
61 	return (buf->buf_addr);
62 }
63 
64 static void
65 sndbuf_setmap(void *arg, bus_dma_segment_t *segs, int nseg, int error)
66 {
67 	struct snd_dbuf *b = (struct snd_dbuf *)arg;
68 
69 	if (bootverbose) {
70 		device_printf(b->dev, "sndbuf_setmap %lx, %lx; ",
71 		    (u_long)segs[0].ds_addr, (u_long)segs[0].ds_len);
72 		printf("%p -> %lx\n", b->buf, (u_long)segs[0].ds_addr);
73 	}
74 	if (error == 0)
75 		b->buf_addr = segs[0].ds_addr;
76 	else
77 		b->buf_addr = 0;
78 }
79 
80 /*
81  * Allocate memory for DMA buffer. If the device does not use DMA transfers,
82  * the driver can call malloc(9) and sndbuf_setup() itself.
83  */
84 
85 int
86 sndbuf_alloc(struct snd_dbuf *b, bus_dma_tag_t dmatag, unsigned int size)
87 {
88 	int ret;
89 
90 	b->dmatag = dmatag;
91 	b->maxsize = size;
92 	b->bufsize = b->maxsize;
93 	b->buf_addr = 0;
94 	b->flags |= SNDBUF_F_MANAGED;
95 	if (bus_dmamem_alloc(b->dmatag, (void **)&b->buf, BUS_DMA_NOWAIT,
96 	    &b->dmamap))
97 		return (ENOMEM);
98 	if (bus_dmamap_load(b->dmatag, b->dmamap, b->buf, b->maxsize,
99 	    sndbuf_setmap, b, 0) != 0 || b->buf_addr == 0) {
100 		bus_dmamem_free(b->dmatag, b->buf, b->dmamap);
101 		b->dmamap = NULL;
102 		return (ENOMEM);
103 	}
104 
105 	ret = sndbuf_resize(b, 2, b->maxsize / 2);
106 	if (ret != 0)
107 		sndbuf_free(b);
108 	return (ret);
109 }
110 
111 int
112 sndbuf_setup(struct snd_dbuf *b, void *buf, unsigned int size)
113 {
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 	b->tmpbuf = NULL;
128 
129 	if (b->shadbuf)
130 		free(b->shadbuf, M_DEVBUF);
131 	b->shadbuf = NULL;
132 	b->sl = 0;
133 
134 	if (!(b->flags & SNDBUF_F_MANAGED) && b->buf)
135 		free(b->buf, M_DEVBUF);
136 
137 	if (b->dmamap)
138 		bus_dmamap_unload(b->dmatag, b->dmamap);
139 
140 	if (b->dmamap && b->buf)
141 		bus_dmamem_free(b->dmatag, b->buf, b->dmamap);
142 	b->dmamap = NULL;
143 	b->buf = NULL;
144 }
145 
146 int
147 sndbuf_resize(struct snd_dbuf *b, unsigned int blkcnt, unsigned int blksz)
148 {
149 	u_int8_t *tmpbuf, *f2;
150 
151 	chn_lock(b->channel);
152 	if (b->maxsize == 0)
153 		goto out;
154 	if (blkcnt == 0)
155 		blkcnt = b->blkcnt;
156 	if (blksz == 0)
157 		blksz = b->blksz;
158 	if (blkcnt < 2 || blksz < 16 || (blkcnt * blksz > b->maxsize)) {
159 		chn_unlock(b->channel);
160 		return EINVAL;
161 	}
162 	if (blkcnt == b->blkcnt && blksz == b->blksz)
163 		goto out;
164 
165 	chn_unlock(b->channel);
166 	tmpbuf = malloc(blkcnt * blksz, M_DEVBUF, M_NOWAIT);
167 	if (tmpbuf == NULL)
168 		return ENOMEM;
169 	chn_lock(b->channel);
170 	b->blkcnt = blkcnt;
171 	b->blksz = blksz;
172 	b->bufsize = blkcnt * blksz;
173 	f2 =  b->tmpbuf;
174 	b->tmpbuf = tmpbuf;
175 	sndbuf_reset(b);
176 	chn_unlock(b->channel);
177 	free(f2, M_DEVBUF);
178 	return 0;
179 out:
180 	chn_unlock(b->channel);
181 	return 0;
182 }
183 
184 int
185 sndbuf_remalloc(struct snd_dbuf *b, unsigned int blkcnt, unsigned int blksz)
186 {
187         u_int8_t *buf, *tmpbuf, *f1, *f2;
188 	u_int8_t *shadbuf, *f3;
189         unsigned int bufsize;
190 	int ret;
191 
192 	if (blkcnt < 2 || blksz < 16)
193 		return EINVAL;
194 
195 	bufsize = blksz * blkcnt;
196 
197 	chn_unlock(b->channel);
198 	buf = malloc(bufsize, M_DEVBUF, M_WAITOK);
199 	tmpbuf = malloc(bufsize, M_DEVBUF, M_WAITOK);
200 	shadbuf = malloc(bufsize, M_DEVBUF, M_WAITOK);
201 
202 	chn_lock(b->channel);
203 
204 	b->blkcnt = blkcnt;
205 	b->blksz = blksz;
206 	b->bufsize = bufsize;
207 	b->maxsize = bufsize;
208 	f1 = b->buf;
209 	f2 = b->tmpbuf;
210 	b->buf = buf;
211 	b->tmpbuf = tmpbuf;
212 	f3 = b->shadbuf;
213 	b->shadbuf = shadbuf;
214 	b->sl = bufsize;
215 
216 	sndbuf_reset(b);
217 
218 	chn_unlock(b->channel);
219       	if (f1)
220 		free(f1, M_DEVBUF);
221       	if (f2)
222 		free(f2, M_DEVBUF);
223 	if (f3)
224 		free(f3, M_DEVBUF);
225 
226 	ret = 0;
227 
228 	chn_lock(b->channel);
229 	return ret;
230 }
231 
232 /**
233  * @brief Zero out space in buffer free area
234  *
235  * This function clears a chunk of @c length bytes in the buffer free area
236  * (i.e., where the next write will be placed).
237  *
238  * @param b		buffer context
239  * @param length	number of bytes to blank
240  */
241 void
242 sndbuf_clear(struct snd_dbuf *b, unsigned int length)
243 {
244 	int i;
245 	u_char data, *p;
246 
247 	if (length == 0)
248 		return;
249 	if (length > b->bufsize)
250 		length = b->bufsize;
251 
252 	data = sndbuf_zerodata(b->fmt);
253 
254 	i = sndbuf_getfreeptr(b);
255 	p = sndbuf_getbuf(b);
256 	while (length > 0) {
257 		p[i] = data;
258 		length--;
259 		i++;
260 		if (i >= b->bufsize)
261 			i = 0;
262 	}
263 }
264 
265 /**
266  * @brief Zap buffer contents, resetting "ready area" fields
267  *
268  * @param b	buffer context
269  */
270 void
271 sndbuf_fillsilence(struct snd_dbuf *b)
272 {
273 	if (b->bufsize > 0)
274 		memset(sndbuf_getbuf(b), sndbuf_zerodata(b->fmt), b->bufsize);
275 	b->rp = 0;
276 	b->rl = b->bufsize;
277 }
278 
279 /**
280  * @brief Reset buffer w/o flushing statistics
281  *
282  * This function just zeroes out buffer contents and sets the "ready length"
283  * to zero.  This was originally to facilitate minimal playback interruption
284  * (i.e., dropped samples) in SNDCTL_DSP_SILENCE/SKIP ioctls.
285  *
286  * @param b	buffer context
287  */
288 void
289 sndbuf_softreset(struct snd_dbuf *b)
290 {
291 	b->rl = 0;
292 	if (b->buf && b->bufsize > 0)
293 		sndbuf_clear(b, b->bufsize);
294 }
295 
296 void
297 sndbuf_reset(struct snd_dbuf *b)
298 {
299 	b->hp = 0;
300 	b->rp = 0;
301 	b->rl = 0;
302 	b->dl = 0;
303 	b->prev_total = 0;
304 	b->total = 0;
305 	b->xrun = 0;
306 	if (b->buf && b->bufsize > 0)
307 		sndbuf_clear(b, b->bufsize);
308 	sndbuf_clearshadow(b);
309 }
310 
311 u_int32_t
312 sndbuf_getfmt(struct snd_dbuf *b)
313 {
314 	return b->fmt;
315 }
316 
317 int
318 sndbuf_setfmt(struct snd_dbuf *b, u_int32_t fmt)
319 {
320 	b->fmt = fmt;
321 	b->bps = 1;
322 	b->bps <<= (b->fmt & AFMT_STEREO)? 1 : 0;
323 	if (b->fmt & AFMT_16BIT)
324 		b->bps <<= 1;
325 	else if (b->fmt & AFMT_24BIT)
326 		b->bps *= 3;
327 	else if (b->fmt & AFMT_32BIT)
328 		b->bps <<= 2;
329 	return 0;
330 }
331 
332 unsigned int
333 sndbuf_getspd(struct snd_dbuf *b)
334 {
335 	return b->spd;
336 }
337 
338 void
339 sndbuf_setspd(struct snd_dbuf *b, unsigned int spd)
340 {
341 	b->spd = spd;
342 }
343 
344 unsigned int
345 sndbuf_getalign(struct snd_dbuf *b)
346 {
347 	static int align[] = {0, 1, 1, 2, 2, 2, 2, 3};
348 
349 	return align[b->bps - 1];
350 }
351 
352 unsigned int
353 sndbuf_getblkcnt(struct snd_dbuf *b)
354 {
355 	return b->blkcnt;
356 }
357 
358 void
359 sndbuf_setblkcnt(struct snd_dbuf *b, unsigned int blkcnt)
360 {
361 	b->blkcnt = blkcnt;
362 }
363 
364 unsigned int
365 sndbuf_getblksz(struct snd_dbuf *b)
366 {
367 	return b->blksz;
368 }
369 
370 void
371 sndbuf_setblksz(struct snd_dbuf *b, unsigned int blksz)
372 {
373 	b->blksz = blksz;
374 }
375 
376 unsigned int
377 sndbuf_getbps(struct snd_dbuf *b)
378 {
379 	return b->bps;
380 }
381 
382 void *
383 sndbuf_getbuf(struct snd_dbuf *b)
384 {
385 	return b->buf;
386 }
387 
388 void *
389 sndbuf_getbufofs(struct snd_dbuf *b, unsigned int ofs)
390 {
391 	KASSERT(ofs < b->bufsize, ("%s: ofs invalid %d", __func__, ofs));
392 
393 	return b->buf + ofs;
394 }
395 
396 unsigned int
397 sndbuf_getsize(struct snd_dbuf *b)
398 {
399 	return b->bufsize;
400 }
401 
402 unsigned int
403 sndbuf_getmaxsize(struct snd_dbuf *b)
404 {
405 	return b->maxsize;
406 }
407 
408 unsigned int
409 sndbuf_runsz(struct snd_dbuf *b)
410 {
411 	return b->dl;
412 }
413 
414 void
415 sndbuf_setrun(struct snd_dbuf *b, int go)
416 {
417 	b->dl = go? b->blksz : 0;
418 }
419 
420 struct selinfo *
421 sndbuf_getsel(struct snd_dbuf *b)
422 {
423 	return &b->sel;
424 }
425 
426 /************************************************************/
427 unsigned int
428 sndbuf_getxrun(struct snd_dbuf *b)
429 {
430 	SNDBUF_LOCKASSERT(b);
431 
432 	return b->xrun;
433 }
434 
435 void
436 sndbuf_setxrun(struct snd_dbuf *b, unsigned int xrun)
437 {
438 	SNDBUF_LOCKASSERT(b);
439 
440 	b->xrun = xrun;
441 }
442 
443 unsigned int
444 sndbuf_gethwptr(struct snd_dbuf *b)
445 {
446 	SNDBUF_LOCKASSERT(b);
447 
448 	return b->hp;
449 }
450 
451 void
452 sndbuf_sethwptr(struct snd_dbuf *b, unsigned int ptr)
453 {
454 	SNDBUF_LOCKASSERT(b);
455 
456 	b->hp = ptr;
457 }
458 
459 unsigned int
460 sndbuf_getready(struct snd_dbuf *b)
461 {
462 	SNDBUF_LOCKASSERT(b);
463 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
464 
465 	return b->rl;
466 }
467 
468 unsigned int
469 sndbuf_getreadyptr(struct snd_dbuf *b)
470 {
471 	SNDBUF_LOCKASSERT(b);
472 	KASSERT((b->rp >= 0) && (b->rp <= b->bufsize), ("%s: b->rp invalid %d", __func__, b->rp));
473 
474 	return b->rp;
475 }
476 
477 unsigned int
478 sndbuf_getfree(struct snd_dbuf *b)
479 {
480 	SNDBUF_LOCKASSERT(b);
481 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
482 
483 	return b->bufsize - b->rl;
484 }
485 
486 unsigned int
487 sndbuf_getfreeptr(struct snd_dbuf *b)
488 {
489 	SNDBUF_LOCKASSERT(b);
490 	KASSERT((b->rp >= 0) && (b->rp <= b->bufsize), ("%s: b->rp invalid %d", __func__, b->rp));
491 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
492 
493 	return (b->rp + b->rl) % b->bufsize;
494 }
495 
496 unsigned int
497 sndbuf_getblocks(struct snd_dbuf *b)
498 {
499 	SNDBUF_LOCKASSERT(b);
500 
501 	return b->total / b->blksz;
502 }
503 
504 unsigned int
505 sndbuf_getprevblocks(struct snd_dbuf *b)
506 {
507 	SNDBUF_LOCKASSERT(b);
508 
509 	return b->prev_total / b->blksz;
510 }
511 
512 unsigned int
513 sndbuf_gettotal(struct snd_dbuf *b)
514 {
515 	SNDBUF_LOCKASSERT(b);
516 
517 	return b->total;
518 }
519 
520 void
521 sndbuf_updateprevtotal(struct snd_dbuf *b)
522 {
523 	SNDBUF_LOCKASSERT(b);
524 
525 	b->prev_total = b->total;
526 }
527 
528 unsigned int
529 snd_xbytes(unsigned int v, unsigned int from, unsigned int to)
530 {
531 	unsigned int w, x, y;
532 
533 	if (from == to)
534 		return v;
535 
536 	if (from == 0 || to == 0 || v == 0)
537 		return 0;
538 
539 	x = from;
540 	y = to;
541 	while (y != 0) {
542 		w = x % y;
543 		x = y;
544 		y = w;
545 	}
546 	from /= x;
547 	to /= x;
548 
549 	return (unsigned int)(((u_int64_t)v * to) / from);
550 }
551 
552 unsigned int
553 sndbuf_xbytes(unsigned int v, struct snd_dbuf *from, struct snd_dbuf *to)
554 {
555 	if (from == NULL || to == NULL || v == 0)
556 		return 0;
557 
558 	return snd_xbytes(v, sndbuf_getbps(from) * sndbuf_getspd(from),
559 	    sndbuf_getbps(to) * sndbuf_getspd(to));
560 }
561 
562 u_int8_t
563 sndbuf_zerodata(u_int32_t fmt)
564 {
565 	if (fmt & AFMT_SIGNED)
566 		return (0x00);
567 	else if (fmt & AFMT_MU_LAW)
568 		return (0x7f);
569 	else if (fmt & AFMT_A_LAW)
570 		return (0x55);
571 	return (0x80);
572 }
573 
574 /************************************************************/
575 
576 /**
577  * @brief Acquire buffer space to extend ready area
578  *
579  * This function extends the ready area length by @c count bytes, and may
580  * optionally copy samples from another location stored in @c from.  The
581  * counter @c snd_dbuf::total is also incremented by @c count bytes.
582  *
583  * @param b	audio buffer
584  * @param from	sample source (optional)
585  * @param count	number of bytes to acquire
586  *
587  * @retval 0	Unconditional
588  */
589 int
590 sndbuf_acquire(struct snd_dbuf *b, u_int8_t *from, unsigned int count)
591 {
592 	int l;
593 
594 	KASSERT(count <= sndbuf_getfree(b), ("%s: count %d > free %d", __func__, count, sndbuf_getfree(b)));
595 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
596 	b->total += count;
597 	if (from != NULL) {
598 		while (count > 0) {
599 			l = min(count, sndbuf_getsize(b) - sndbuf_getfreeptr(b));
600 			bcopy(from, sndbuf_getbufofs(b, sndbuf_getfreeptr(b)), l);
601 			from += l;
602 			b->rl += l;
603 			count -= l;
604 		}
605 	} else
606 		b->rl += count;
607 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d, count %d", __func__, b->rl, count));
608 
609 	return 0;
610 }
611 
612 /**
613  * @brief Dispose samples from channel buffer, increasing size of ready area
614  *
615  * This function discards samples from the supplied buffer by advancing the
616  * ready area start pointer and decrementing the ready area length.  If
617  * @c to is not NULL, then the discard samples will be copied to the location
618  * it points to.
619  *
620  * @param b	PCM channel sound buffer
621  * @param to	destination buffer (optional)
622  * @param count	number of bytes to discard
623  *
624  * @returns 0 unconditionally
625  */
626 int
627 sndbuf_dispose(struct snd_dbuf *b, u_int8_t *to, unsigned int count)
628 {
629 	int l;
630 
631 	KASSERT(count <= sndbuf_getready(b), ("%s: count %d > ready %d", __func__, count, sndbuf_getready(b)));
632 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d", __func__, b->rl));
633 	if (to != NULL) {
634 		while (count > 0) {
635 			l = min(count, sndbuf_getsize(b) - sndbuf_getreadyptr(b));
636 			bcopy(sndbuf_getbufofs(b, sndbuf_getreadyptr(b)), to, l);
637 			to += l;
638 			b->rl -= l;
639 			b->rp = (b->rp + l) % b->bufsize;
640 			count -= l;
641 		}
642 	} else {
643 		b->rl -= count;
644 		b->rp = (b->rp + count) % b->bufsize;
645 	}
646 	KASSERT((b->rl >= 0) && (b->rl <= b->bufsize), ("%s: b->rl invalid %d, count %d", __func__, b->rl, count));
647 
648 	return 0;
649 }
650 
651 /* count is number of bytes we want added to destination buffer */
652 int
653 sndbuf_feed(struct snd_dbuf *from, struct snd_dbuf *to, struct pcm_channel *channel, struct pcm_feeder *feeder, unsigned int count)
654 {
655 	unsigned int cnt;
656 
657 	KASSERT(count > 0, ("can't feed 0 bytes"));
658 
659 	if (sndbuf_getfree(to) < count)
660 		return EINVAL;
661 
662 	do {
663 		cnt = FEEDER_FEED(feeder, channel, to->tmpbuf, count, from);
664 		if (cnt)
665 			sndbuf_acquire(to, to->tmpbuf, cnt);
666 		/* the root feeder has called sndbuf_dispose(from, , bytes fetched) */
667 		count -= cnt;
668 	} while (count && cnt);
669 
670 	return 0;
671 }
672 
673 /************************************************************/
674 
675 void
676 sndbuf_dump(struct snd_dbuf *b, char *s, u_int32_t what)
677 {
678 	printf("%s: [", s);
679 	if (what & 0x01)
680 		printf(" bufsize: %d, maxsize: %d", b->bufsize, b->maxsize);
681 	if (what & 0x02)
682 		printf(" dl: %d, rp: %d, rl: %d, hp: %d", b->dl, b->rp, b->rl, b->hp);
683 	if (what & 0x04)
684 		printf(" total: %d, prev_total: %d, xrun: %d", b->total, b->prev_total, b->xrun);
685    	if (what & 0x08)
686 		printf(" fmt: 0x%x, spd: %d", b->fmt, b->spd);
687 	if (what & 0x10)
688 		printf(" blksz: %d, blkcnt: %d, flags: 0x%x", b->blksz, b->blkcnt, b->flags);
689 	printf(" ]\n");
690 }
691 
692 /************************************************************/
693 u_int32_t
694 sndbuf_getflags(struct snd_dbuf *b)
695 {
696 	return b->flags;
697 }
698 
699 void
700 sndbuf_setflags(struct snd_dbuf *b, u_int32_t flags, int on)
701 {
702 	b->flags &= ~flags;
703 	if (on)
704 		b->flags |= flags;
705 }
706 
707 /**
708  * @brief Clear the shadow buffer by filling with samples equal to zero.
709  *
710  * @param b buffer to clear
711  */
712 void
713 sndbuf_clearshadow(struct snd_dbuf *b)
714 {
715 	KASSERT(b != NULL, ("b is a null pointer"));
716 	KASSERT(b->sl >= 0, ("illegal shadow length"));
717 
718 	if ((b->shadbuf != NULL) && (b->sl > 0))
719 		memset(b->shadbuf, sndbuf_zerodata(b->fmt), b->sl);
720 }
721 
722 #ifdef OSSV4_EXPERIMENT
723 /**
724  * @brief Return peak value from samples in buffer ready area.
725  *
726  * Peak ranges from 0-32767.  If channel is monaural, most significant 16
727  * bits will be zero.  For now, only expects to work with 1-2 channel
728  * buffers.
729  *
730  * @note  Currently only operates with linear PCM formats.
731  *
732  * @param b buffer to analyze
733  * @param lpeak pointer to store left peak value
734  * @param rpeak pointer to store right peak value
735  */
736 void
737 sndbuf_getpeaks(struct snd_dbuf *b, int *lp, int *rp)
738 {
739 	u_int32_t lpeak, rpeak;
740 
741 	lpeak = 0;
742 	rpeak = 0;
743 
744 	/**
745 	 * @todo fill this in later
746 	 */
747 }
748 #endif
749