xref: /linux/sound/xen/xen_snd_front_alsa.c (revision 4b132aacb0768ac1e652cf517097ea6f237214b9)
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 static const struct alsa_sndif_sample_format ALSA_SNDIF_FORMATS[] = {
73 	{
74 		.sndif = XENSND_PCM_FORMAT_U8,
75 		.alsa = SNDRV_PCM_FORMAT_U8
76 	},
77 	{
78 		.sndif = XENSND_PCM_FORMAT_S8,
79 		.alsa = SNDRV_PCM_FORMAT_S8
80 	},
81 	{
82 		.sndif = XENSND_PCM_FORMAT_U16_LE,
83 		.alsa = SNDRV_PCM_FORMAT_U16_LE
84 	},
85 	{
86 		.sndif = XENSND_PCM_FORMAT_U16_BE,
87 		.alsa = SNDRV_PCM_FORMAT_U16_BE
88 	},
89 	{
90 		.sndif = XENSND_PCM_FORMAT_S16_LE,
91 		.alsa = SNDRV_PCM_FORMAT_S16_LE
92 	},
93 	{
94 		.sndif = XENSND_PCM_FORMAT_S16_BE,
95 		.alsa = SNDRV_PCM_FORMAT_S16_BE
96 	},
97 	{
98 		.sndif = XENSND_PCM_FORMAT_U24_LE,
99 		.alsa = SNDRV_PCM_FORMAT_U24_LE
100 	},
101 	{
102 		.sndif = XENSND_PCM_FORMAT_U24_BE,
103 		.alsa = SNDRV_PCM_FORMAT_U24_BE
104 	},
105 	{
106 		.sndif = XENSND_PCM_FORMAT_S24_LE,
107 		.alsa = SNDRV_PCM_FORMAT_S24_LE
108 	},
109 	{
110 		.sndif = XENSND_PCM_FORMAT_S24_BE,
111 		.alsa = SNDRV_PCM_FORMAT_S24_BE
112 	},
113 	{
114 		.sndif = XENSND_PCM_FORMAT_U32_LE,
115 		.alsa = SNDRV_PCM_FORMAT_U32_LE
116 	},
117 	{
118 		.sndif = XENSND_PCM_FORMAT_U32_BE,
119 		.alsa = SNDRV_PCM_FORMAT_U32_BE
120 	},
121 	{
122 		.sndif = XENSND_PCM_FORMAT_S32_LE,
123 		.alsa = SNDRV_PCM_FORMAT_S32_LE
124 	},
125 	{
126 		.sndif = XENSND_PCM_FORMAT_S32_BE,
127 		.alsa = SNDRV_PCM_FORMAT_S32_BE
128 	},
129 	{
130 		.sndif = XENSND_PCM_FORMAT_A_LAW,
131 		.alsa = SNDRV_PCM_FORMAT_A_LAW
132 	},
133 	{
134 		.sndif = XENSND_PCM_FORMAT_MU_LAW,
135 		.alsa = SNDRV_PCM_FORMAT_MU_LAW
136 	},
137 	{
138 		.sndif = XENSND_PCM_FORMAT_F32_LE,
139 		.alsa = SNDRV_PCM_FORMAT_FLOAT_LE
140 	},
141 	{
142 		.sndif = XENSND_PCM_FORMAT_F32_BE,
143 		.alsa = SNDRV_PCM_FORMAT_FLOAT_BE
144 	},
145 	{
146 		.sndif = XENSND_PCM_FORMAT_F64_LE,
147 		.alsa = SNDRV_PCM_FORMAT_FLOAT64_LE
148 	},
149 	{
150 		.sndif = XENSND_PCM_FORMAT_F64_BE,
151 		.alsa = SNDRV_PCM_FORMAT_FLOAT64_BE
152 	},
153 	{
154 		.sndif = XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE,
155 		.alsa = SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE
156 	},
157 	{
158 		.sndif = XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE,
159 		.alsa = SNDRV_PCM_FORMAT_IEC958_SUBFRAME_BE
160 	},
161 	{
162 		.sndif = XENSND_PCM_FORMAT_IMA_ADPCM,
163 		.alsa = SNDRV_PCM_FORMAT_IMA_ADPCM
164 	},
165 	{
166 		.sndif = XENSND_PCM_FORMAT_MPEG,
167 		.alsa = SNDRV_PCM_FORMAT_MPEG
168 	},
169 	{
170 		.sndif = XENSND_PCM_FORMAT_GSM,
171 		.alsa = SNDRV_PCM_FORMAT_GSM
172 	},
173 };
174 
175 static int to_sndif_format(snd_pcm_format_t format)
176 {
177 	int i;
178 
179 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
180 		if (ALSA_SNDIF_FORMATS[i].alsa == format)
181 			return ALSA_SNDIF_FORMATS[i].sndif;
182 
183 	return -EINVAL;
184 }
185 
186 static u64 to_sndif_formats_mask(u64 alsa_formats)
187 {
188 	u64 mask;
189 	int i;
190 
191 	mask = 0;
192 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
193 		if (pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa) & alsa_formats)
194 			mask |= BIT_ULL(ALSA_SNDIF_FORMATS[i].sndif);
195 
196 	return mask;
197 }
198 
199 static u64 to_alsa_formats_mask(u64 sndif_formats)
200 {
201 	u64 mask;
202 	int i;
203 
204 	mask = 0;
205 	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
206 		if (BIT_ULL(ALSA_SNDIF_FORMATS[i].sndif) & sndif_formats)
207 			mask |= pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa);
208 
209 	return mask;
210 }
211 
212 static void stream_clear(struct xen_snd_front_pcm_stream_info *stream)
213 {
214 	stream->is_open = false;
215 	stream->be_cur_frame = 0;
216 	stream->out_frames = 0;
217 	atomic_set(&stream->hw_ptr, 0);
218 	xen_snd_front_evtchnl_pair_clear(stream->evt_pair);
219 	memset(&stream->shbuf, 0, sizeof(stream->shbuf));
220 	stream->buffer = NULL;
221 	stream->buffer_sz = 0;
222 	stream->pages = NULL;
223 	stream->num_pages = 0;
224 }
225 
226 static void stream_free(struct xen_snd_front_pcm_stream_info *stream)
227 {
228 	xen_front_pgdir_shbuf_unmap(&stream->shbuf);
229 	xen_front_pgdir_shbuf_free(&stream->shbuf);
230 	if (stream->buffer)
231 		free_pages_exact(stream->buffer, stream->buffer_sz);
232 	kfree(stream->pages);
233 	stream_clear(stream);
234 }
235 
236 static struct xen_snd_front_pcm_stream_info *
237 stream_get(struct snd_pcm_substream *substream)
238 {
239 	struct xen_snd_front_pcm_instance_info *pcm_instance =
240 			snd_pcm_substream_chip(substream);
241 	struct xen_snd_front_pcm_stream_info *stream;
242 
243 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
244 		stream = &pcm_instance->streams_pb[substream->number];
245 	else
246 		stream = &pcm_instance->streams_cap[substream->number];
247 
248 	return stream;
249 }
250 
251 static int alsa_hw_rule(struct snd_pcm_hw_params *params,
252 			struct snd_pcm_hw_rule *rule)
253 {
254 	struct xen_snd_front_pcm_stream_info *stream = rule->private;
255 	struct device *dev = &stream->front_info->xb_dev->dev;
256 	struct snd_mask *formats =
257 			hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
258 	struct snd_interval *rates =
259 			hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
260 	struct snd_interval *channels =
261 			hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
262 	struct snd_interval *period =
263 			hw_param_interval(params,
264 					  SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
265 	struct snd_interval *buffer =
266 			hw_param_interval(params,
267 					  SNDRV_PCM_HW_PARAM_BUFFER_SIZE);
268 	struct xensnd_query_hw_param req;
269 	struct xensnd_query_hw_param resp;
270 	struct snd_interval interval;
271 	struct snd_mask mask;
272 	u64 sndif_formats;
273 	int changed, ret;
274 
275 	/* Collect all the values we need for the query. */
276 
277 	req.formats = to_sndif_formats_mask((u64)formats->bits[0] |
278 					    (u64)(formats->bits[1]) << 32);
279 
280 	req.rates.min = rates->min;
281 	req.rates.max = rates->max;
282 
283 	req.channels.min = channels->min;
284 	req.channels.max = channels->max;
285 
286 	req.buffer.min = buffer->min;
287 	req.buffer.max = buffer->max;
288 
289 	req.period.min = period->min;
290 	req.period.max = period->max;
291 
292 	ret = xen_snd_front_stream_query_hw_param(&stream->evt_pair->req,
293 						  &req, &resp);
294 	if (ret < 0) {
295 		/* Check if this is due to backend communication error. */
296 		if (ret == -EIO || ret == -ETIMEDOUT)
297 			dev_err(dev, "Failed to query ALSA HW parameters\n");
298 		return ret;
299 	}
300 
301 	/* Refine HW parameters after the query. */
302 	changed  = 0;
303 
304 	sndif_formats = to_alsa_formats_mask(resp.formats);
305 	snd_mask_none(&mask);
306 	mask.bits[0] = (u32)sndif_formats;
307 	mask.bits[1] = (u32)(sndif_formats >> 32);
308 	ret = snd_mask_refine(formats, &mask);
309 	if (ret < 0)
310 		return ret;
311 	changed |= ret;
312 
313 	interval.openmin = 0;
314 	interval.openmax = 0;
315 	interval.integer = 1;
316 
317 	interval.min = resp.rates.min;
318 	interval.max = resp.rates.max;
319 	ret = snd_interval_refine(rates, &interval);
320 	if (ret < 0)
321 		return ret;
322 	changed |= ret;
323 
324 	interval.min = resp.channels.min;
325 	interval.max = resp.channels.max;
326 	ret = snd_interval_refine(channels, &interval);
327 	if (ret < 0)
328 		return ret;
329 	changed |= ret;
330 
331 	interval.min = resp.buffer.min;
332 	interval.max = resp.buffer.max;
333 	ret = snd_interval_refine(buffer, &interval);
334 	if (ret < 0)
335 		return ret;
336 	changed |= ret;
337 
338 	interval.min = resp.period.min;
339 	interval.max = resp.period.max;
340 	ret = snd_interval_refine(period, &interval);
341 	if (ret < 0)
342 		return ret;
343 	changed |= ret;
344 
345 	return changed;
346 }
347 
348 static int alsa_open(struct snd_pcm_substream *substream)
349 {
350 	struct xen_snd_front_pcm_instance_info *pcm_instance =
351 			snd_pcm_substream_chip(substream);
352 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
353 	struct snd_pcm_runtime *runtime = substream->runtime;
354 	struct xen_snd_front_info *front_info =
355 			pcm_instance->card_info->front_info;
356 	struct device *dev = &front_info->xb_dev->dev;
357 	int ret;
358 
359 	/*
360 	 * Return our HW properties: override defaults with those configured
361 	 * via XenStore.
362 	 */
363 	runtime->hw = stream->pcm_hw;
364 	runtime->hw.info &= ~(SNDRV_PCM_INFO_MMAP |
365 			      SNDRV_PCM_INFO_MMAP_VALID |
366 			      SNDRV_PCM_INFO_DOUBLE |
367 			      SNDRV_PCM_INFO_BATCH |
368 			      SNDRV_PCM_INFO_NONINTERLEAVED |
369 			      SNDRV_PCM_INFO_RESUME |
370 			      SNDRV_PCM_INFO_PAUSE);
371 	runtime->hw.info |= SNDRV_PCM_INFO_INTERLEAVED;
372 
373 	stream->evt_pair = &front_info->evt_pairs[stream->index];
374 
375 	stream->front_info = front_info;
376 
377 	stream->evt_pair->evt.u.evt.substream = substream;
378 
379 	stream_clear(stream);
380 
381 	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, true);
382 
383 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT,
384 				  alsa_hw_rule, stream,
385 				  SNDRV_PCM_HW_PARAM_FORMAT, -1);
386 	if (ret) {
387 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_FORMAT\n");
388 		return ret;
389 	}
390 
391 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
392 				  alsa_hw_rule, stream,
393 				  SNDRV_PCM_HW_PARAM_RATE, -1);
394 	if (ret) {
395 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_RATE\n");
396 		return ret;
397 	}
398 
399 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
400 				  alsa_hw_rule, stream,
401 				  SNDRV_PCM_HW_PARAM_CHANNELS, -1);
402 	if (ret) {
403 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_CHANNELS\n");
404 		return ret;
405 	}
406 
407 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
408 				  alsa_hw_rule, stream,
409 				  SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
410 	if (ret) {
411 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_PERIOD_SIZE\n");
412 		return ret;
413 	}
414 
415 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
416 				  alsa_hw_rule, stream,
417 				  SNDRV_PCM_HW_PARAM_BUFFER_SIZE, -1);
418 	if (ret) {
419 		dev_err(dev, "Failed to add HW rule for SNDRV_PCM_HW_PARAM_BUFFER_SIZE\n");
420 		return ret;
421 	}
422 
423 	return 0;
424 }
425 
426 static int alsa_close(struct snd_pcm_substream *substream)
427 {
428 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
429 
430 	xen_snd_front_evtchnl_pair_set_connected(stream->evt_pair, false);
431 	return 0;
432 }
433 
434 static int shbuf_setup_backstore(struct xen_snd_front_pcm_stream_info *stream,
435 				 size_t buffer_sz)
436 {
437 	int i;
438 
439 	stream->buffer = alloc_pages_exact(buffer_sz, GFP_KERNEL);
440 	if (!stream->buffer)
441 		return -ENOMEM;
442 
443 	stream->buffer_sz = buffer_sz;
444 	stream->num_pages = DIV_ROUND_UP(stream->buffer_sz, PAGE_SIZE);
445 	stream->pages = kcalloc(stream->num_pages, sizeof(struct page *),
446 				GFP_KERNEL);
447 	if (!stream->pages)
448 		return -ENOMEM;
449 
450 	for (i = 0; i < stream->num_pages; i++)
451 		stream->pages[i] = virt_to_page(stream->buffer + i * PAGE_SIZE);
452 
453 	return 0;
454 }
455 
456 static int alsa_hw_params(struct snd_pcm_substream *substream,
457 			  struct snd_pcm_hw_params *params)
458 {
459 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
460 	struct xen_snd_front_info *front_info = stream->front_info;
461 	struct xen_front_pgdir_shbuf_cfg buf_cfg;
462 	int ret;
463 
464 	/*
465 	 * This callback may be called multiple times,
466 	 * so free the previously allocated shared buffer if any.
467 	 */
468 	stream_free(stream);
469 	ret = shbuf_setup_backstore(stream, params_buffer_bytes(params));
470 	if (ret < 0)
471 		goto fail;
472 
473 	memset(&buf_cfg, 0, sizeof(buf_cfg));
474 	buf_cfg.xb_dev = front_info->xb_dev;
475 	buf_cfg.pgdir = &stream->shbuf;
476 	buf_cfg.num_pages = stream->num_pages;
477 	buf_cfg.pages = stream->pages;
478 
479 	ret = xen_front_pgdir_shbuf_alloc(&buf_cfg);
480 	if (ret < 0)
481 		goto fail;
482 
483 	ret = xen_front_pgdir_shbuf_map(&stream->shbuf);
484 	if (ret < 0)
485 		goto fail;
486 
487 	return 0;
488 
489 fail:
490 	stream_free(stream);
491 	dev_err(&front_info->xb_dev->dev,
492 		"Failed to allocate buffers for stream with index %d\n",
493 		stream->index);
494 	return ret;
495 }
496 
497 static int alsa_hw_free(struct snd_pcm_substream *substream)
498 {
499 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
500 	int ret;
501 
502 	ret = xen_snd_front_stream_close(&stream->evt_pair->req);
503 	stream_free(stream);
504 	return ret;
505 }
506 
507 static int alsa_prepare(struct snd_pcm_substream *substream)
508 {
509 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
510 
511 	if (!stream->is_open) {
512 		struct snd_pcm_runtime *runtime = substream->runtime;
513 		u8 sndif_format;
514 		int ret;
515 
516 		ret = to_sndif_format(runtime->format);
517 		if (ret < 0) {
518 			dev_err(&stream->front_info->xb_dev->dev,
519 				"Unsupported sample format: %d\n",
520 				runtime->format);
521 			return ret;
522 		}
523 		sndif_format = ret;
524 
525 		ret = xen_snd_front_stream_prepare(&stream->evt_pair->req,
526 						   &stream->shbuf,
527 						   sndif_format,
528 						   runtime->channels,
529 						   runtime->rate,
530 						   snd_pcm_lib_buffer_bytes(substream),
531 						   snd_pcm_lib_period_bytes(substream));
532 		if (ret < 0)
533 			return ret;
534 
535 		stream->is_open = true;
536 	}
537 
538 	return 0;
539 }
540 
541 static int alsa_trigger(struct snd_pcm_substream *substream, int cmd)
542 {
543 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
544 	int type;
545 
546 	switch (cmd) {
547 	case SNDRV_PCM_TRIGGER_START:
548 		type = XENSND_OP_TRIGGER_START;
549 		break;
550 
551 	case SNDRV_PCM_TRIGGER_RESUME:
552 		type = XENSND_OP_TRIGGER_RESUME;
553 		break;
554 
555 	case SNDRV_PCM_TRIGGER_STOP:
556 		type = XENSND_OP_TRIGGER_STOP;
557 		break;
558 
559 	case SNDRV_PCM_TRIGGER_SUSPEND:
560 		type = XENSND_OP_TRIGGER_PAUSE;
561 		break;
562 
563 	default:
564 		return -EINVAL;
565 	}
566 
567 	return xen_snd_front_stream_trigger(&stream->evt_pair->req, type);
568 }
569 
570 void xen_snd_front_alsa_handle_cur_pos(struct xen_snd_front_evtchnl *evtchnl,
571 				       u64 pos_bytes)
572 {
573 	struct snd_pcm_substream *substream = evtchnl->u.evt.substream;
574 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
575 	snd_pcm_uframes_t delta, new_hw_ptr, cur_frame;
576 
577 	cur_frame = bytes_to_frames(substream->runtime, pos_bytes);
578 
579 	delta = cur_frame - stream->be_cur_frame;
580 	stream->be_cur_frame = cur_frame;
581 
582 	new_hw_ptr = (snd_pcm_uframes_t)atomic_read(&stream->hw_ptr);
583 	new_hw_ptr = (new_hw_ptr + delta) % substream->runtime->buffer_size;
584 	atomic_set(&stream->hw_ptr, (int)new_hw_ptr);
585 
586 	stream->out_frames += delta;
587 	if (stream->out_frames > substream->runtime->period_size) {
588 		stream->out_frames %= substream->runtime->period_size;
589 		snd_pcm_period_elapsed(substream);
590 	}
591 }
592 
593 static snd_pcm_uframes_t alsa_pointer(struct snd_pcm_substream *substream)
594 {
595 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
596 
597 	return (snd_pcm_uframes_t)atomic_read(&stream->hw_ptr);
598 }
599 
600 static int alsa_pb_copy(struct snd_pcm_substream *substream,
601 			int channel, unsigned long pos, struct iov_iter *src,
602 			unsigned long count)
603 {
604 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
605 
606 	if (unlikely(pos + count > stream->buffer_sz))
607 		return -EINVAL;
608 
609 	if (copy_from_iter(stream->buffer + pos, count, src) != count)
610 		return -EFAULT;
611 
612 	return xen_snd_front_stream_write(&stream->evt_pair->req, pos, count);
613 }
614 
615 static int alsa_cap_copy(struct snd_pcm_substream *substream,
616 			 int channel, unsigned long pos, struct iov_iter *dst,
617 			 unsigned long count)
618 {
619 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
620 	int ret;
621 
622 	if (unlikely(pos + count > stream->buffer_sz))
623 		return -EINVAL;
624 
625 	ret = xen_snd_front_stream_read(&stream->evt_pair->req, pos, count);
626 	if (ret < 0)
627 		return ret;
628 
629 	if (copy_to_iter(stream->buffer + pos, count, dst) != count)
630 		return -EFAULT;
631 	return 0;
632 }
633 
634 static int alsa_pb_fill_silence(struct snd_pcm_substream *substream,
635 				int channel, unsigned long pos,
636 				unsigned long count)
637 {
638 	struct xen_snd_front_pcm_stream_info *stream = stream_get(substream);
639 
640 	if (unlikely(pos + count > stream->buffer_sz))
641 		return -EINVAL;
642 
643 	memset(stream->buffer + pos, 0, count);
644 
645 	return xen_snd_front_stream_write(&stream->evt_pair->req, pos, count);
646 }
647 
648 /*
649  * FIXME: The mmaped data transfer is asynchronous and there is no
650  * ack signal from user-space when it is done. This is the
651  * reason it is not implemented in the PV driver as we do need
652  * to know when the buffer can be transferred to the backend.
653  */
654 
655 static const struct snd_pcm_ops snd_drv_alsa_playback_ops = {
656 	.open		= alsa_open,
657 	.close		= alsa_close,
658 	.hw_params	= alsa_hw_params,
659 	.hw_free	= alsa_hw_free,
660 	.prepare	= alsa_prepare,
661 	.trigger	= alsa_trigger,
662 	.pointer	= alsa_pointer,
663 	.copy		= alsa_pb_copy,
664 	.fill_silence	= alsa_pb_fill_silence,
665 };
666 
667 static const struct snd_pcm_ops snd_drv_alsa_capture_ops = {
668 	.open		= alsa_open,
669 	.close		= alsa_close,
670 	.hw_params	= alsa_hw_params,
671 	.hw_free	= alsa_hw_free,
672 	.prepare	= alsa_prepare,
673 	.trigger	= alsa_trigger,
674 	.pointer	= alsa_pointer,
675 	.copy		= alsa_cap_copy,
676 };
677 
678 static int new_pcm_instance(struct xen_snd_front_card_info *card_info,
679 			    struct xen_front_cfg_pcm_instance *instance_cfg,
680 			    struct xen_snd_front_pcm_instance_info *pcm_instance_info)
681 {
682 	struct snd_pcm *pcm;
683 	int ret, i;
684 
685 	dev_dbg(&card_info->front_info->xb_dev->dev,
686 		"New PCM device \"%s\" with id %d playback %d capture %d",
687 		instance_cfg->name,
688 		instance_cfg->device_id,
689 		instance_cfg->num_streams_pb,
690 		instance_cfg->num_streams_cap);
691 
692 	pcm_instance_info->card_info = card_info;
693 
694 	pcm_instance_info->pcm_hw = instance_cfg->pcm_hw;
695 
696 	if (instance_cfg->num_streams_pb) {
697 		pcm_instance_info->streams_pb =
698 				devm_kcalloc(&card_info->card->card_dev,
699 					     instance_cfg->num_streams_pb,
700 					     sizeof(struct xen_snd_front_pcm_stream_info),
701 					     GFP_KERNEL);
702 		if (!pcm_instance_info->streams_pb)
703 			return -ENOMEM;
704 	}
705 
706 	if (instance_cfg->num_streams_cap) {
707 		pcm_instance_info->streams_cap =
708 				devm_kcalloc(&card_info->card->card_dev,
709 					     instance_cfg->num_streams_cap,
710 					     sizeof(struct xen_snd_front_pcm_stream_info),
711 					     GFP_KERNEL);
712 		if (!pcm_instance_info->streams_cap)
713 			return -ENOMEM;
714 	}
715 
716 	pcm_instance_info->num_pcm_streams_pb =
717 			instance_cfg->num_streams_pb;
718 	pcm_instance_info->num_pcm_streams_cap =
719 			instance_cfg->num_streams_cap;
720 
721 	for (i = 0; i < pcm_instance_info->num_pcm_streams_pb; i++) {
722 		pcm_instance_info->streams_pb[i].pcm_hw =
723 			instance_cfg->streams_pb[i].pcm_hw;
724 		pcm_instance_info->streams_pb[i].index =
725 			instance_cfg->streams_pb[i].index;
726 	}
727 
728 	for (i = 0; i < pcm_instance_info->num_pcm_streams_cap; i++) {
729 		pcm_instance_info->streams_cap[i].pcm_hw =
730 			instance_cfg->streams_cap[i].pcm_hw;
731 		pcm_instance_info->streams_cap[i].index =
732 			instance_cfg->streams_cap[i].index;
733 	}
734 
735 	ret = snd_pcm_new(card_info->card, instance_cfg->name,
736 			  instance_cfg->device_id,
737 			  instance_cfg->num_streams_pb,
738 			  instance_cfg->num_streams_cap,
739 			  &pcm);
740 	if (ret < 0)
741 		return ret;
742 
743 	pcm->private_data = pcm_instance_info;
744 	pcm->info_flags = 0;
745 	/* we want to handle all PCM operations in non-atomic context */
746 	pcm->nonatomic = true;
747 	strscpy(pcm->name, "Virtual card PCM", sizeof(pcm->name));
748 
749 	if (instance_cfg->num_streams_pb)
750 		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK,
751 				&snd_drv_alsa_playback_ops);
752 
753 	if (instance_cfg->num_streams_cap)
754 		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE,
755 				&snd_drv_alsa_capture_ops);
756 
757 	pcm_instance_info->pcm = pcm;
758 	return 0;
759 }
760 
761 int xen_snd_front_alsa_init(struct xen_snd_front_info *front_info)
762 {
763 	struct device *dev = &front_info->xb_dev->dev;
764 	struct xen_front_cfg_card *cfg = &front_info->cfg;
765 	struct xen_snd_front_card_info *card_info;
766 	struct snd_card *card;
767 	int ret, i;
768 
769 	dev_dbg(dev, "Creating virtual sound card\n");
770 
771 	ret = snd_card_new(dev, 0, XENSND_DRIVER_NAME, THIS_MODULE,
772 			   sizeof(struct xen_snd_front_card_info), &card);
773 	if (ret < 0)
774 		return ret;
775 
776 	card_info = card->private_data;
777 	card_info->front_info = front_info;
778 	front_info->card_info = card_info;
779 	card_info->card = card;
780 	card_info->pcm_instances =
781 			devm_kcalloc(dev, cfg->num_pcm_instances,
782 				     sizeof(struct xen_snd_front_pcm_instance_info),
783 				     GFP_KERNEL);
784 	if (!card_info->pcm_instances) {
785 		ret = -ENOMEM;
786 		goto fail;
787 	}
788 
789 	card_info->num_pcm_instances = cfg->num_pcm_instances;
790 	card_info->pcm_hw = cfg->pcm_hw;
791 
792 	for (i = 0; i < cfg->num_pcm_instances; i++) {
793 		ret = new_pcm_instance(card_info, &cfg->pcm_instances[i],
794 				       &card_info->pcm_instances[i]);
795 		if (ret < 0)
796 			goto fail;
797 	}
798 
799 	strscpy(card->driver, XENSND_DRIVER_NAME, sizeof(card->driver));
800 	strscpy(card->shortname, cfg->name_short, sizeof(card->shortname));
801 	strscpy(card->longname, cfg->name_long, sizeof(card->longname));
802 
803 	ret = snd_card_register(card);
804 	if (ret < 0)
805 		goto fail;
806 
807 	return 0;
808 
809 fail:
810 	snd_card_free(card);
811 	return ret;
812 }
813 
814 void xen_snd_front_alsa_fini(struct xen_snd_front_info *front_info)
815 {
816 	struct xen_snd_front_card_info *card_info;
817 	struct snd_card *card;
818 
819 	card_info = front_info->card_info;
820 	if (!card_info)
821 		return;
822 
823 	card = card_info->card;
824 	if (!card)
825 		return;
826 
827 	dev_dbg(&front_info->xb_dev->dev, "Removing virtual sound card %d\n",
828 		card->number);
829 	snd_card_free(card);
830 
831 	/* Card_info will be freed when destroying front_info->xb_dev->dev. */
832 	card_info->card = NULL;
833 }
834