xref: /linux/sound/xen/xen_snd_front_alsa.c (revision f85f5ae45ad945270a8884261de8249431e8b5a6)
1 // SPDX-License-Identifier: GPL-2.0 OR MIT
2 
3 /*
4  * Xen para-virtual sound device
5  *
6  * Copyright (C) 2016-2018 EPAM Systems Inc.
7  *
8  * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
9  */
10 
11 #include <linux/platform_device.h>
12 
13 #include <sound/core.h>
14 #include <sound/pcm.h>
15 #include <sound/pcm_params.h>
16 
17 #include <xen/xenbus.h>
18 #include <xen/xen-front-pgdir-shbuf.h>
19 
20 #include "xen_snd_front.h"
21 #include "xen_snd_front_alsa.h"
22 #include "xen_snd_front_cfg.h"
23 #include "xen_snd_front_evtchnl.h"
24 
25 struct xen_snd_front_pcm_stream_info {
26 	struct xen_snd_front_info *front_info;
27 	struct xen_snd_front_evtchnl_pair *evt_pair;
28 
29 	/* This is the shared buffer with its backing storage. */
30 	struct xen_front_pgdir_shbuf shbuf;
31 	u8 *buffer;
32 	size_t buffer_sz;
33 	int num_pages;
34 	struct page **pages;
35 
36 	int index;
37 
38 	bool is_open;
39 	struct snd_pcm_hardware pcm_hw;
40 
41 	/* Number of processed frames as reported by the backend. */
42 	snd_pcm_uframes_t be_cur_frame;
43 	/* Current HW pointer to be reported via .period callback. */
44 	atomic_t hw_ptr;
45 	/* Modulo of the number of processed frames - for period detection. */
46 	u32 out_frames;
47 };
48 
49 struct xen_snd_front_pcm_instance_info {
50 	struct xen_snd_front_card_info *card_info;
51 	struct snd_pcm *pcm;
52 	struct snd_pcm_hardware pcm_hw;
53 	int num_pcm_streams_pb;
54 	struct xen_snd_front_pcm_stream_info *streams_pb;
55 	int num_pcm_streams_cap;
56 	struct xen_snd_front_pcm_stream_info *streams_cap;
57 };
58 
59 struct xen_snd_front_card_info {
60 	struct xen_snd_front_info *front_info;
61 	struct snd_card *card;
62 	struct snd_pcm_hardware pcm_hw;
63 	int num_pcm_instances;
64 	struct xen_snd_front_pcm_instance_info *pcm_instances;
65 };
66 
67 struct alsa_sndif_sample_format {
68 	u8 sndif;
69 	snd_pcm_format_t alsa;
70 };
71 
72 struct alsa_sndif_hw_param {
73 	u8 sndif;
74 	snd_pcm_hw_param_t alsa;
75 };
76 
77 static const struct alsa_sndif_sample_format ALSA_SNDIF_FORMATS[] = {
78 	{
79 		.sndif = XENSND_PCM_FORMAT_U8,
80 		.alsa = SNDRV_PCM_FORMAT_U8
81 	},
82 	{
83 		.sndif = XENSND_PCM_FORMAT_S8,
84 		.alsa = SNDRV_PCM_FORMAT_S8
85 	},
86 	{
87 		.sndif = XENSND_PCM_FORMAT_U16_LE,
88 		.alsa = SNDRV_PCM_FORMAT_U16_LE
89 	},
90 	{
91 		.sndif = XENSND_PCM_FORMAT_U16_BE,
92 		.alsa = SNDRV_PCM_FORMAT_U16_BE
93 	},
94 	{
95 		.sndif = XENSND_PCM_FORMAT_S16_LE,
96 		.alsa = SNDRV_PCM_FORMAT_S16_LE
97 	},
98 	{
99 		.sndif = XENSND_PCM_FORMAT_S16_BE,
100 		.alsa = SNDRV_PCM_FORMAT_S16_BE
101 	},
102 	{
103 		.sndif = XENSND_PCM_FORMAT_U24_LE,
104 		.alsa = SNDRV_PCM_FORMAT_U24_LE
105 	},
106 	{
107 		.sndif = XENSND_PCM_FORMAT_U24_BE,
108 		.alsa = SNDRV_PCM_FORMAT_U24_BE
109 	},
110 	{
111 		.sndif = XENSND_PCM_FORMAT_S24_LE,
112 		.alsa = SNDRV_PCM_FORMAT_S24_LE
113 	},
114 	{
115 		.sndif = XENSND_PCM_FORMAT_S24_BE,
116 		.alsa = SNDRV_PCM_FORMAT_S24_BE
117 	},
118 	{
119 		.sndif = XENSND_PCM_FORMAT_U32_LE,
120 		.alsa = SNDRV_PCM_FORMAT_U32_LE
121 	},
122 	{
123 		.sndif = XENSND_PCM_FORMAT_U32_BE,
124 		.alsa = SNDRV_PCM_FORMAT_U32_BE
125 	},
126 	{
127 		.sndif = XENSND_PCM_FORMAT_S32_LE,
128 		.alsa = SNDRV_PCM_FORMAT_S32_LE
129 	},
130 	{
131 		.sndif = XENSND_PCM_FORMAT_S32_BE,
132 		.alsa = SNDRV_PCM_FORMAT_S32_BE
133 	},
134 	{
135 		.sndif = XENSND_PCM_FORMAT_A_LAW,
136 		.alsa = SNDRV_PCM_FORMAT_A_LAW
137 	},
138 	{
139 		.sndif = XENSND_PCM_FORMAT_MU_LAW,
140 		.alsa = SNDRV_PCM_FORMAT_MU_LAW
141 	},
142 	{
143 		.sndif = XENSND_PCM_FORMAT_F32_LE,
144 		.alsa = SNDRV_PCM_FORMAT_FLOAT_LE
145 	},
146 	{
147 		.sndif = XENSND_PCM_FORMAT_F32_BE,
148 		.alsa = SNDRV_PCM_FORMAT_FLOAT_BE
149 	},
150 	{
151 		.sndif = XENSND_PCM_FORMAT_F64_LE,
152 		.alsa = SNDRV_PCM_FORMAT_FLOAT64_LE
153 	},
154 	{
155 		.sndif = XENSND_PCM_FORMAT_F64_BE,
156 		.alsa = SNDRV_PCM_FORMAT_FLOAT64_BE
157 	},
158 	{
159 		.sndif = XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE,
160 		.alsa = SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE
161 	},
162 	{
163 		.sndif = XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE,
164 		.alsa = SNDRV_PCM_FORMAT_IEC958_SUBFRAME_BE
165 	},
166 	{
167 		.sndif = XENSND_PCM_FORMAT_IMA_ADPCM,
168 		.alsa = SNDRV_PCM_FORMAT_IMA_ADPCM
169 	},
170 	{
171 		.sndif = XENSND_PCM_FORMAT_MPEG,
172 		.alsa = SNDRV_PCM_FORMAT_MPEG
173 	},
174 	{
175 		.sndif = XENSND_PCM_FORMAT_GSM,
176 		.alsa = SNDRV_PCM_FORMAT_GSM
177 	},
178 };
179 
180 static int to_sndif_format(snd_pcm_format_t format)
181 {
182 	int i;
183 
184 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
185 		if (ALSA_SNDIF_FORMATS[i].alsa == format)
186 			return ALSA_SNDIF_FORMATS[i].sndif;
187 
188 	return -EINVAL;
189 }
190 
191 static u64 to_sndif_formats_mask(u64 alsa_formats)
192 {
193 	u64 mask;
194 	int i;
195 
196 	mask = 0;
197 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
198 		if (pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa) & alsa_formats)
199 			mask |= BIT_ULL(ALSA_SNDIF_FORMATS[i].sndif);
200 
201 	return mask;
202 }
203 
204 static u64 to_alsa_formats_mask(u64 sndif_formats)
205 {
206 	u64 mask;
207 	int i;
208 
209 	mask = 0;
210 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
211 		if (BIT_ULL(ALSA_SNDIF_FORMATS[i].sndif) & sndif_formats)
212 			mask |= pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa);
213 
214 	return mask;
215 }
216 
217 static void stream_clear(struct xen_snd_front_pcm_stream_info *stream)
218 {
219 	stream->is_open = false;
220 	stream->be_cur_frame = 0;
221 	stream->out_frames = 0;
222 	atomic_set(&stream->hw_ptr, 0);
223 	xen_snd_front_evtchnl_pair_clear(stream->evt_pair);
224 	memset(&stream->shbuf, 0, sizeof(stream->shbuf));
225 	stream->buffer = NULL;
226 	stream->buffer_sz = 0;
227 	stream->pages = NULL;
228 	stream->num_pages = 0;
229 }
230 
231 static void stream_free(struct xen_snd_front_pcm_stream_info *stream)
232 {
233 	xen_front_pgdir_shbuf_unmap(&stream->shbuf);
234 	xen_front_pgdir_shbuf_free(&stream->shbuf);
235 	if (stream->buffer)
236 		free_pages_exact(stream->buffer, stream->buffer_sz);
237 	kfree(stream->pages);
238 	stream_clear(stream);
239 }
240 
241 static struct xen_snd_front_pcm_stream_info *
242 stream_get(struct snd_pcm_substream *substream)
243 {
244 	struct xen_snd_front_pcm_instance_info *pcm_instance =
245 			snd_pcm_substream_chip(substream);
246 	struct xen_snd_front_pcm_stream_info *stream;
247 
248 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
249 		stream = &pcm_instance->streams_pb[substream->number];
250 	else
251 		stream = &pcm_instance->streams_cap[substream->number];
252 
253 	return stream;
254 }
255 
256 static int alsa_hw_rule(struct snd_pcm_hw_params *params,
257 			struct snd_pcm_hw_rule *rule)
258 {
259 	struct xen_snd_front_pcm_stream_info *stream = rule->private;
260 	struct device *dev = &stream->front_info->xb_dev->dev;
261 	struct snd_mask *formats =
262 			hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
263 	struct snd_interval *rates =
264 			hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
265 	struct snd_interval *channels =
266 			hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
267 	struct snd_interval *period =
268 			hw_param_interval(params,
269 					  SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
270 	struct snd_interval *buffer =
271 			hw_param_interval(params,
272 					  SNDRV_PCM_HW_PARAM_BUFFER_SIZE);
273 	struct xensnd_query_hw_param req;
274 	struct xensnd_query_hw_param resp;
275 	struct snd_interval interval;
276 	struct snd_mask mask;
277 	u64 sndif_formats;
278 	int changed, ret;
279 
280 	/* Collect all the values we need for the query. */
281 
282 	req.formats = to_sndif_formats_mask((u64)formats->bits[0] |
283 					    (u64)(formats->bits[1]) << 32);
284 
285 	req.rates.min = rates->min;
286 	req.rates.max = rates->max;
287 
288 	req.channels.min = channels->min;
289 	req.channels.max = channels->max;
290 
291 	req.buffer.min = buffer->min;
292 	req.buffer.max = buffer->max;
293 
294 	req.period.min = period->min;
295 	req.period.max = period->max;
296 
297 	ret = xen_snd_front_stream_query_hw_param(&stream->evt_pair->req,
298 						  &req, &resp);
299 	if (ret < 0) {
300 		/* Check if this is due to backend communication error. */
301 		if (ret == -EIO || ret == -ETIMEDOUT)
302 			dev_err(dev, "Failed to query ALSA HW parameters\n");
303 		return ret;
304 	}
305 
306 	/* Refine HW parameters after the query. */
307 	changed  = 0;
308 
309 	sndif_formats = to_alsa_formats_mask(resp.formats);
310 	snd_mask_none(&mask);
311 	mask.bits[0] = (u32)sndif_formats;
312 	mask.bits[1] = (u32)(sndif_formats >> 32);
313 	ret = snd_mask_refine(formats, &mask);
314 	if (ret < 0)
315 		return ret;
316 	changed |= ret;
317 
318 	interval.openmin = 0;
319 	interval.openmax = 0;
320 	interval.integer = 1;
321 
322 	interval.min = resp.rates.min;
323 	interval.max = resp.rates.max;
324 	ret = snd_interval_refine(rates, &interval);
325 	if (ret < 0)
326 		return ret;
327 	changed |= ret;
328 
329 	interval.min = resp.channels.min;
330 	interval.max = resp.channels.max;
331 	ret = snd_interval_refine(channels, &interval);
332 	if (ret < 0)
333 		return ret;
334 	changed |= ret;
335 
336 	interval.min = resp.buffer.min;
337 	interval.max = resp.buffer.max;
338 	ret = snd_interval_refine(buffer, &interval);
339 	if (ret < 0)
340 		return ret;
341 	changed |= ret;
342 
343 	interval.min = resp.period.min;
344 	interval.max = resp.period.max;
345 	ret = snd_interval_refine(period, &interval);
346 	if (ret < 0)
347 		return ret;
348 	changed |= ret;
349 
350 	return changed;
351 }
352 
353 static int alsa_open(struct snd_pcm_substream *substream)
354 {
355 	struct xen_snd_front_pcm_instance_info *pcm_instance =
356 			snd_pcm_substream_chip(substream);
357 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
358 	struct snd_pcm_runtime *runtime = substream->runtime;
359 	struct xen_snd_front_info *front_info =
360 			pcm_instance->card_info->front_info;
361 	struct device *dev = &front_info->xb_dev->dev;
362 	int ret;
363 
364 	/*
365 	 * Return our HW properties: override defaults with those configured
366 	 * via XenStore.
367 	 */
368 	runtime->hw = stream->pcm_hw;
369 	runtime->hw.info &= ~(SNDRV_PCM_INFO_MMAP |
370 			      SNDRV_PCM_INFO_MMAP_VALID |
371 			      SNDRV_PCM_INFO_DOUBLE |
372 			      SNDRV_PCM_INFO_BATCH |
373 			      SNDRV_PCM_INFO_NONINTERLEAVED |
374 			      SNDRV_PCM_INFO_RESUME |
375 			      SNDRV_PCM_INFO_PAUSE);
376 	runtime->hw.info |= SNDRV_PCM_INFO_INTERLEAVED;
377 
378 	stream->evt_pair = &front_info->evt_pairs[stream->index];
379 
380 	stream->front_info = front_info;
381 
382 	stream->evt_pair->evt.u.evt.substream = substream;
383 
384 	stream_clear(stream);
385 
386 	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, true);
387 
388 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT,
389 				  alsa_hw_rule, stream,
390 				  SNDRV_PCM_HW_PARAM_FORMAT, -1);
391 	if (ret) {
392 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_FORMAT\n");
393 		return ret;
394 	}
395 
396 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
397 				  alsa_hw_rule, stream,
398 				  SNDRV_PCM_HW_PARAM_RATE, -1);
399 	if (ret) {
400 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_RATE\n");
401 		return ret;
402 	}
403 
404 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
405 				  alsa_hw_rule, stream,
406 				  SNDRV_PCM_HW_PARAM_CHANNELS, -1);
407 	if (ret) {
408 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_CHANNELS\n");
409 		return ret;
410 	}
411 
412 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
413 				  alsa_hw_rule, stream,
414 				  SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
415 	if (ret) {
416 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_PERIOD_SIZE\n");
417 		return ret;
418 	}
419 
420 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
421 				  alsa_hw_rule, stream,
422 				  SNDRV_PCM_HW_PARAM_BUFFER_SIZE, -1);
423 	if (ret) {
424 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_BUFFER_SIZE\n");
425 		return ret;
426 	}
427 
428 	return 0;
429 }
430 
431 static int alsa_close(struct snd_pcm_substream *substream)
432 {
433 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
434 
435 	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, false);
436 	return 0;
437 }
438 
439 static int shbuf_setup_backstore(struct xen_snd_front_pcm_stream_info *stream,
440 				 size_t buffer_sz)
441 {
442 	int i;
443 
444 	stream->buffer = alloc_pages_exact(buffer_sz, GFP_KERNEL);
445 	if (!stream->buffer)
446 		return -ENOMEM;
447 
448 	stream->buffer_sz = buffer_sz;
449 	stream->num_pages = DIV_ROUND_UP(stream->buffer_sz, PAGE_SIZE);
450 	stream->pages = kcalloc(stream->num_pages, sizeof(struct page *),
451 				GFP_KERNEL);
452 	if (!stream->pages)
453 		return -ENOMEM;
454 
455 	for (i = 0; i < stream->num_pages; i++)
456 		stream->pages[i] = virt_to_page(stream->buffer + i * PAGE_SIZE);
457 
458 	return 0;
459 }
460 
461 static int alsa_hw_params(struct snd_pcm_substream *substream,
462 			  struct snd_pcm_hw_params *params)
463 {
464 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
465 	struct xen_snd_front_info *front_info = stream->front_info;
466 	struct xen_front_pgdir_shbuf_cfg buf_cfg;
467 	int ret;
468 
469 	/*
470 	 * This callback may be called multiple times,
471 	 * so free the previously allocated shared buffer if any.
472 	 */
473 	stream_free(stream);
474 	ret = shbuf_setup_backstore(stream, params_buffer_bytes(params));
475 	if (ret < 0)
476 		goto fail;
477 
478 	memset(&buf_cfg, 0, sizeof(buf_cfg));
479 	buf_cfg.xb_dev = front_info->xb_dev;
480 	buf_cfg.pgdir = &stream->shbuf;
481 	buf_cfg.num_pages = stream->num_pages;
482 	buf_cfg.pages = stream->pages;
483 
484 	ret = xen_front_pgdir_shbuf_alloc(&buf_cfg);
485 	if (ret < 0)
486 		goto fail;
487 
488 	ret = xen_front_pgdir_shbuf_map(&stream->shbuf);
489 	if (ret < 0)
490 		goto fail;
491 
492 	return 0;
493 
494 fail:
495 	stream_free(stream);
496 	dev_err(&front_info->xb_dev->dev,
497 		"Failed to allocate buffers for stream with index %d\n",
498 		stream->index);
499 	return ret;
500 }
501 
502 static int alsa_hw_free(struct snd_pcm_substream *substream)
503 {
504 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
505 	int ret;
506 
507 	ret = xen_snd_front_stream_close(&stream->evt_pair->req);
508 	stream_free(stream);
509 	return ret;
510 }
511 
512 static int alsa_prepare(struct snd_pcm_substream *substream)
513 {
514 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
515 
516 	if (!stream->is_open) {
517 		struct snd_pcm_runtime *runtime = substream->runtime;
518 		u8 sndif_format;
519 		int ret;
520 
521 		ret = to_sndif_format(runtime->format);
522 		if (ret < 0) {
523 			dev_err(&stream->front_info->xb_dev->dev,
524 				"Unsupported sample format: %d\n",
525 				runtime->format);
526 			return ret;
527 		}
528 		sndif_format = ret;
529 
530 		ret = xen_snd_front_stream_prepare(&stream->evt_pair->req,
531 						   &stream->shbuf,
532 						   sndif_format,
533 						   runtime->channels,
534 						   runtime->rate,
535 						   snd_pcm_lib_buffer_bytes(substream),
536 						   snd_pcm_lib_period_bytes(substream));
537 		if (ret < 0)
538 			return ret;
539 
540 		stream->is_open = true;
541 	}
542 
543 	return 0;
544 }
545 
546 static int alsa_trigger(struct snd_pcm_substream *substream, int cmd)
547 {
548 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
549 	int type;
550 
551 	switch (cmd) {
552 	case SNDRV_PCM_TRIGGER_START:
553 		type = XENSND_OP_TRIGGER_START;
554 		break;
555 
556 	case SNDRV_PCM_TRIGGER_RESUME:
557 		type = XENSND_OP_TRIGGER_RESUME;
558 		break;
559 
560 	case SNDRV_PCM_TRIGGER_STOP:
561 		type = XENSND_OP_TRIGGER_STOP;
562 		break;
563 
564 	case SNDRV_PCM_TRIGGER_SUSPEND:
565 		type = XENSND_OP_TRIGGER_PAUSE;
566 		break;
567 
568 	default:
569 		return -EINVAL;
570 	}
571 
572 	return xen_snd_front_stream_trigger(&stream->evt_pair->req, type);
573 }
574 
575 void xen_snd_front_alsa_handle_cur_pos(struct xen_snd_front_evtchnl *evtchnl,
576 				       u64 pos_bytes)
577 {
578 	struct snd_pcm_substream *substream = evtchnl->u.evt.substream;
579 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
580 	snd_pcm_uframes_t delta, new_hw_ptr, cur_frame;
581 
582 	cur_frame = bytes_to_frames(substream->runtime, pos_bytes);
583 
584 	delta = cur_frame - stream->be_cur_frame;
585 	stream->be_cur_frame = cur_frame;
586 
587 	new_hw_ptr = (snd_pcm_uframes_t)atomic_read(&stream->hw_ptr);
588 	new_hw_ptr = (new_hw_ptr + delta) % substream->runtime->buffer_size;
589 	atomic_set(&stream->hw_ptr, (int)new_hw_ptr);
590 
591 	stream->out_frames += delta;
592 	if (stream->out_frames > substream->runtime->period_size) {
593 		stream->out_frames %= substream->runtime->period_size;
594 		snd_pcm_period_elapsed(substream);
595 	}
596 }
597 
598 static snd_pcm_uframes_t alsa_pointer(struct snd_pcm_substream *substream)
599 {
600 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
601 
602 	return (snd_pcm_uframes_t)atomic_read(&stream->hw_ptr);
603 }
604 
605 static int alsa_pb_copy(struct snd_pcm_substream *substream,
606 			int channel, unsigned long pos, struct iov_iter *src,
607 			unsigned long count)
608 {
609 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
610 
611 	if (unlikely(pos + count > stream->buffer_sz))
612 		return -EINVAL;
613 
614 	if (copy_from_iter(stream->buffer + pos, count, src) != count)
615 		return -EFAULT;
616 
617 	return xen_snd_front_stream_write(&stream->evt_pair->req, pos, count);
618 }
619 
620 static int alsa_cap_copy(struct snd_pcm_substream *substream,
621 			 int channel, unsigned long pos, struct iov_iter *dst,
622 			 unsigned long count)
623 {
624 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
625 	int ret;
626 
627 	if (unlikely(pos + count > stream->buffer_sz))
628 		return -EINVAL;
629 
630 	ret = xen_snd_front_stream_read(&stream->evt_pair->req, pos, count);
631 	if (ret < 0)
632 		return ret;
633 
634 	if (copy_to_iter(stream->buffer + pos, count, dst) != count)
635 		return -EFAULT;
636 	return 0;
637 }
638 
639 static int alsa_pb_fill_silence(struct snd_pcm_substream *substream,
640 				int channel, unsigned long pos,
641 				unsigned long count)
642 {
643 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
644 
645 	if (unlikely(pos + count > stream->buffer_sz))
646 		return -EINVAL;
647 
648 	memset(stream->buffer + pos, 0, count);
649 
650 	return xen_snd_front_stream_write(&stream->evt_pair->req, pos, count);
651 }
652 
653 /*
654  * FIXME: The mmaped data transfer is asynchronous and there is no
655  * ack signal from user-space when it is done. This is the
656  * reason it is not implemented in the PV driver as we do need
657  * to know when the buffer can be transferred to the backend.
658  */
659 
660 static const struct snd_pcm_ops snd_drv_alsa_playback_ops = {
661 	.open		= alsa_open,
662 	.close		= alsa_close,
663 	.hw_params	= alsa_hw_params,
664 	.hw_free	= alsa_hw_free,
665 	.prepare	= alsa_prepare,
666 	.trigger	= alsa_trigger,
667 	.pointer	= alsa_pointer,
668 	.copy		= alsa_pb_copy,
669 	.fill_silence	= alsa_pb_fill_silence,
670 };
671 
672 static const struct snd_pcm_ops snd_drv_alsa_capture_ops = {
673 	.open		= alsa_open,
674 	.close		= alsa_close,
675 	.hw_params	= alsa_hw_params,
676 	.hw_free	= alsa_hw_free,
677 	.prepare	= alsa_prepare,
678 	.trigger	= alsa_trigger,
679 	.pointer	= alsa_pointer,
680 	.copy		= alsa_cap_copy,
681 };
682 
683 static int new_pcm_instance(struct xen_snd_front_card_info *card_info,
684 			    struct xen_front_cfg_pcm_instance *instance_cfg,
685 			    struct xen_snd_front_pcm_instance_info *pcm_instance_info)
686 {
687 	struct snd_pcm *pcm;
688 	int ret, i;
689 
690 	dev_dbg(&card_info->front_info->xb_dev->dev,
691 		"New PCM device \"%s\" with id %d playback %d capture %d",
692 		instance_cfg->name,
693 		instance_cfg->device_id,
694 		instance_cfg->num_streams_pb,
695 		instance_cfg->num_streams_cap);
696 
697 	pcm_instance_info->card_info = card_info;
698 
699 	pcm_instance_info->pcm_hw = instance_cfg->pcm_hw;
700 
701 	if (instance_cfg->num_streams_pb) {
702 		pcm_instance_info->streams_pb =
703 				devm_kcalloc(&card_info->card->card_dev,
704 					     instance_cfg->num_streams_pb,
705 					     sizeof(struct xen_snd_front_pcm_stream_info),
706 					     GFP_KERNEL);
707 		if (!pcm_instance_info->streams_pb)
708 			return -ENOMEM;
709 	}
710 
711 	if (instance_cfg->num_streams_cap) {
712 		pcm_instance_info->streams_cap =
713 				devm_kcalloc(&card_info->card->card_dev,
714 					     instance_cfg->num_streams_cap,
715 					     sizeof(struct xen_snd_front_pcm_stream_info),
716 					     GFP_KERNEL);
717 		if (!pcm_instance_info->streams_cap)
718 			return -ENOMEM;
719 	}
720 
721 	pcm_instance_info->num_pcm_streams_pb =
722 			instance_cfg->num_streams_pb;
723 	pcm_instance_info->num_pcm_streams_cap =
724 			instance_cfg->num_streams_cap;
725 
726 	for (i = 0; i < pcm_instance_info->num_pcm_streams_pb; i++) {
727 		pcm_instance_info->streams_pb[i].pcm_hw =
728 			instance_cfg->streams_pb[i].pcm_hw;
729 		pcm_instance_info->streams_pb[i].index =
730 			instance_cfg->streams_pb[i].index;
731 	}
732 
733 	for (i = 0; i < pcm_instance_info->num_pcm_streams_cap; i++) {
734 		pcm_instance_info->streams_cap[i].pcm_hw =
735 			instance_cfg->streams_cap[i].pcm_hw;
736 		pcm_instance_info->streams_cap[i].index =
737 			instance_cfg->streams_cap[i].index;
738 	}
739 
740 	ret = snd_pcm_new(card_info->card, instance_cfg->name,
741 			  instance_cfg->device_id,
742 			  instance_cfg->num_streams_pb,
743 			  instance_cfg->num_streams_cap,
744 			  &pcm);
745 	if (ret < 0)
746 		return ret;
747 
748 	pcm->private_data = pcm_instance_info;
749 	pcm->info_flags = 0;
750 	/* we want to handle all PCM operations in non-atomic context */
751 	pcm->nonatomic = true;
752 	strscpy(pcm->name, "Virtual card PCM", sizeof(pcm->name));
753 
754 	if (instance_cfg->num_streams_pb)
755 		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK,
756 				&snd_drv_alsa_playback_ops);
757 
758 	if (instance_cfg->num_streams_cap)
759 		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE,
760 				&snd_drv_alsa_capture_ops);
761 
762 	pcm_instance_info->pcm = pcm;
763 	return 0;
764 }
765 
766 int xen_snd_front_alsa_init(struct xen_snd_front_info *front_info)
767 {
768 	struct device *dev = &front_info->xb_dev->dev;
769 	struct xen_front_cfg_card *cfg = &front_info->cfg;
770 	struct xen_snd_front_card_info *card_info;
771 	struct snd_card *card;
772 	int ret, i;
773 
774 	dev_dbg(dev, "Creating virtual sound card\n");
775 
776 	ret = snd_card_new(dev, 0, XENSND_DRIVER_NAME, THIS_MODULE,
777 			   sizeof(struct xen_snd_front_card_info), &card);
778 	if (ret < 0)
779 		return ret;
780 
781 	card_info = card->private_data;
782 	card_info->front_info = front_info;
783 	front_info->card_info = card_info;
784 	card_info->card = card;
785 	card_info->pcm_instances =
786 			devm_kcalloc(dev, cfg->num_pcm_instances,
787 				     sizeof(struct xen_snd_front_pcm_instance_info),
788 				     GFP_KERNEL);
789 	if (!card_info->pcm_instances) {
790 		ret = -ENOMEM;
791 		goto fail;
792 	}
793 
794 	card_info->num_pcm_instances = cfg->num_pcm_instances;
795 	card_info->pcm_hw = cfg->pcm_hw;
796 
797 	for (i = 0; i < cfg->num_pcm_instances; i++) {
798 		ret = new_pcm_instance(card_info, &cfg->pcm_instances[i],
799 				       &card_info->pcm_instances[i]);
800 		if (ret < 0)
801 			goto fail;
802 	}
803 
804 	strscpy(card->driver, XENSND_DRIVER_NAME, sizeof(card->driver));
805 	strscpy(card->shortname, cfg->name_short, sizeof(card->shortname));
806 	strscpy(card->longname, cfg->name_long, sizeof(card->longname));
807 
808 	ret = snd_card_register(card);
809 	if (ret < 0)
810 		goto fail;
811 
812 	return 0;
813 
814 fail:
815 	snd_card_free(card);
816 	return ret;
817 }
818 
819 void xen_snd_front_alsa_fini(struct xen_snd_front_info *front_info)
820 {
821 	struct xen_snd_front_card_info *card_info;
822 	struct snd_card *card;
823 
824 	card_info = front_info->card_info;
825 	if (!card_info)
826 		return;
827 
828 	card = card_info->card;
829 	if (!card)
830 		return;
831 
832 	dev_dbg(&front_info->xb_dev->dev, "Removing virtual sound card %d\n",
833 		card->number);
834 	snd_card_free(card);
835 
836 	/* Card_info will be freed when destroying front_info->xb_dev->dev. */
837 	card_info->card = NULL;
838 }
839