Re: [PATCH v2 4/9] ALSA: virtio: build PCM devices and substream hardware descriptors

On Sun, 24 Jan 2021, Anton Yakovlev wrote:

Like the HDA specification, the virtio sound device specification links PCM substreams, jacks and PCM channel maps into functional groups. For each discovered group, a PCM device is created, the number of which coincides with the group number.

Introduce the module parameters for setting the hardware buffer parameters: pcm_buffer_ms [=160] pcm_periods_min [=2] pcm_periods_max [=16] pcm_period_ms_min [=10] pcm_period_ms_max [=80]

Signed-off-by: Anton Yakovlev anton.yakovlev@opensynergy.com

sound/virtio/Makefile | 3 +- sound/virtio/virtio_card.c | 45 ++++ sound/virtio/virtio_card.h | 9 + sound/virtio/virtio_pcm.c | 536 +++++++++++++++++++++++++++++++++++++ sound/virtio/virtio_pcm.h | 89 ++++++ 5 files changed, 681 insertions(+), 1 deletion(-) create mode 100644 sound/virtio/virtio_pcm.c create mode 100644 sound/virtio/virtio_pcm.h

diff --git a/sound/virtio/Makefile b/sound/virtio/Makefile index dc551e637441..69162a545a41 100644 --- a/sound/virtio/Makefile +++ b/sound/virtio/Makefile @@ -4,5 +4,6 @@ obj-$(CONFIG_SND_VIRTIO) += virtio_snd.o

virtio_snd-objs := \ virtio_card.o \

• virtio_ctl_msg.o

• virtio_ctl_msg.o \
• virtio_pcm.o

diff --git a/sound/virtio/virtio_card.c b/sound/virtio/virtio_card.c index 955eadc2d858..39fe13b43dd1 100644 --- a/sound/virtio/virtio_card.c +++ b/sound/virtio/virtio_card.c @@ -92,6 +92,17 @@ static void virtsnd_event_notify_cb(struct virtqueue *vqueue) if (!event) break;

• 	switch (le32_to_cpu(event->hdr.code)) {
  

• 	case VIRTIO_SND_EVT_PCM_PERIOD_ELAPSED:
  

• 	case VIRTIO_SND_EVT_PCM_XRUN: {
  

In the previous patch you had a switch-case statement complying to the common kernel coding style. It isn't specified in coding-style.rst, but these superfluous braces really don't seem to be good for anything - in this and multiple other switch-case statements in the series.

• 		virtsnd_pcm_event(snd, event);
  

• 		break;
  

• 	}
  

• 	default: {
  

• 		break;
  

An empty default doesn't seem very useful either. So the above could've just been

+ switch (le32_to_cpu(event->hdr.code)) { + case VIRTIO_SND_EVT_PCM_PERIOD_ELAPSED: + case VIRTIO_SND_EVT_PCM_XRUN: + virtsnd_pcm_event(snd, event); + }

• 	}
  

• 	}
  

• virtsnd_event_send(queue->vqueue, event, true,
  		   GFP_ATOMIC);
  

  }

@@ -274,6 +285,16 @@ static int virtsnd_build_devs(struct virtio_snd *snd) strscpy(snd->card->longname, "VirtIO Sound Card", sizeof(snd->card->longname));

• rc = virtsnd_pcm_parse_cfg(snd);
• if (rc)

• return rc;
  

• if (snd->nsubstreams) {

• rc = virtsnd_pcm_build_devs(snd);
  

• if (rc)
  

• 	return rc;
  

• }
• return snd_card_register(snd->card);

}

@@ -302,6 +323,9 @@ static int virtsnd_validate(struct virtio_device *vdev) return -EINVAL; }

• if (virtsnd_pcm_validate(vdev))

• return -EINVAL;
  

• return 0;

}

@@ -325,6 +349,7 @@ static int virtsnd_probe(struct virtio_device *vdev) snd->vdev = vdev; INIT_WORK(&snd->reset_work, virtsnd_reset_fn); INIT_LIST_HEAD(&snd->ctl_msgs);

• INIT_LIST_HEAD(&snd->pcm_list);

  vdev->priv = snd;

@@ -359,6 +384,8 @@ static int virtsnd_probe(struct virtio_device *vdev) static void virtsnd_remove(struct virtio_device *vdev) { struct virtio_snd *snd = vdev->priv;

• struct virtio_pcm *pcm;

• struct virtio_pcm *pcm_next;

  if (!snd) return;

@@ -376,6 +403,24 @@ static void virtsnd_remove(struct virtio_device *vdev) vdev->config->reset(vdev); vdev->config->del_vqs(vdev);

• list_for_each_entry_safe(pcm, pcm_next, &snd->pcm_list, list) {

• unsigned int i;
  

• list_del(&pcm->list);
  

• for (i = 0; i < ARRAY_SIZE(pcm->streams); ++i) {
  

• 	struct virtio_pcm_stream *stream = &pcm->streams[i];
  

• 	if (stream->substreams)
  

• 		devm_kfree(&vdev->dev, stream->substreams);
  

• }
  

• devm_kfree(&vdev->dev, pcm);
  

Please double-check both devm_kfree() calls above. Probably they aren't needed in the .remove() method.

• }

• if (snd->substreams)

• devm_kfree(&vdev->dev, snd->substreams);
  

• devm_kfree(&vdev->dev, snd);

  vdev->priv = NULL;

diff --git a/sound/virtio/virtio_card.h b/sound/virtio/virtio_card.h index 37b734a92134..be6651a6aaf8 100644 --- a/sound/virtio/virtio_card.h +++ b/sound/virtio/virtio_card.h @@ -24,6 +24,9 @@ #include <uapi/linux/virtio_snd.h>

#include "virtio_ctl_msg.h" +#include "virtio_pcm.h"

+struct virtio_pcm_substream;

/**

• struct virtio_snd_queue - Virtqueue wrapper structure.

@@ -43,6 +46,9 @@ struct virtio_snd_queue {

• @card: ALSA sound card.
• @ctl_msgs: Pending control request list.
• @event_msgs: Device events.

• • @pcm_list: VirtIO PCM device list.
• • @substreams: VirtIO PCM substreams.
• • @nsubstreams: Number of PCM substreams.

*/ struct virtio_snd { struct virtio_device *vdev; @@ -51,6 +57,9 @@ struct virtio_snd { struct snd_card *card; struct list_head ctl_msgs; struct virtio_snd_event *event_msgs;

• struct list_head pcm_list;
• struct virtio_pcm_substream *substreams;
• unsigned int nsubstreams;

};

/* Message completion timeout in milliseconds (module parameter). */ diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c new file mode 100644 index 000000000000..036990b7b78a --- /dev/null +++ b/sound/virtio/virtio_pcm.c @@ -0,0 +1,536 @@ +// SPDX-License-Identifier: GPL-2.0+ +/*

• • Sound card driver for virtio
• • Copyright (C) 2020 OpenSynergy GmbH
• • This program is free software; you can redistribute it and/or modify
• • it under the terms of the GNU General Public License as published by
• • the Free Software Foundation; either version 2 of the License, or
• • (at your option) any later version.
• • This program is distributed in the hope that it will be useful,
• • but WITHOUT ANY WARRANTY; without even the implied warranty of
• • MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
• • GNU General Public License for more details.
• • You should have received a copy of the GNU General Public License
• • along with this program; if not, see http://www.gnu.org/licenses/.
• */

+#include <linux/moduleparam.h> +#include <linux/virtio_config.h>

+#include "virtio_card.h"

+static unsigned int pcm_buffer_ms = 160; +module_param(pcm_buffer_ms, uint, 0644); +MODULE_PARM_DESC(pcm_buffer_ms, "PCM substream buffer time in milliseconds");

+static unsigned int pcm_periods_min = 2; +module_param(pcm_periods_min, uint, 0644); +MODULE_PARM_DESC(pcm_periods_min, "Minimum number of PCM periods");

+static unsigned int pcm_periods_max = 16; +module_param(pcm_periods_max, uint, 0644); +MODULE_PARM_DESC(pcm_periods_max, "Maximum number of PCM periods");

+static unsigned int pcm_period_ms_min = 10; +module_param(pcm_period_ms_min, uint, 0644); +MODULE_PARM_DESC(pcm_period_ms_min, "Minimum PCM period time in milliseconds");

+static unsigned int pcm_period_ms_max = 80; +module_param(pcm_period_ms_max, uint, 0644); +MODULE_PARM_DESC(pcm_period_ms_max, "Maximum PCM period time in milliseconds");

+/* Map for converting VirtIO format to ALSA format. */ +static const unsigned int g_v2a_format_map[] = {

• [VIRTIO_SND_PCM_FMT_IMA_ADPCM] = SNDRV_PCM_FORMAT_IMA_ADPCM,
• [VIRTIO_SND_PCM_FMT_MU_LAW] = SNDRV_PCM_FORMAT_MU_LAW,
• [VIRTIO_SND_PCM_FMT_A_LAW] = SNDRV_PCM_FORMAT_A_LAW,
• [VIRTIO_SND_PCM_FMT_S8] = SNDRV_PCM_FORMAT_S8,
• [VIRTIO_SND_PCM_FMT_U8] = SNDRV_PCM_FORMAT_U8,
• [VIRTIO_SND_PCM_FMT_S16] = SNDRV_PCM_FORMAT_S16_LE,
• [VIRTIO_SND_PCM_FMT_U16] = SNDRV_PCM_FORMAT_U16_LE,
• [VIRTIO_SND_PCM_FMT_S18_3] = SNDRV_PCM_FORMAT_S18_3LE,
• [VIRTIO_SND_PCM_FMT_U18_3] = SNDRV_PCM_FORMAT_U18_3LE,
• [VIRTIO_SND_PCM_FMT_S20_3] = SNDRV_PCM_FORMAT_S20_3LE,
• [VIRTIO_SND_PCM_FMT_U20_3] = SNDRV_PCM_FORMAT_U20_3LE,
• [VIRTIO_SND_PCM_FMT_S24_3] = SNDRV_PCM_FORMAT_S24_3LE,
• [VIRTIO_SND_PCM_FMT_U24_3] = SNDRV_PCM_FORMAT_U24_3LE,
• [VIRTIO_SND_PCM_FMT_S20] = SNDRV_PCM_FORMAT_S20_LE,
• [VIRTIO_SND_PCM_FMT_U20] = SNDRV_PCM_FORMAT_U20_LE,
• [VIRTIO_SND_PCM_FMT_S24] = SNDRV_PCM_FORMAT_S24_LE,
• [VIRTIO_SND_PCM_FMT_U24] = SNDRV_PCM_FORMAT_U24_LE,
• [VIRTIO_SND_PCM_FMT_S32] = SNDRV_PCM_FORMAT_S32_LE,
• [VIRTIO_SND_PCM_FMT_U32] = SNDRV_PCM_FORMAT_U32_LE,
• [VIRTIO_SND_PCM_FMT_FLOAT] = SNDRV_PCM_FORMAT_FLOAT_LE,
• [VIRTIO_SND_PCM_FMT_FLOAT64] = SNDRV_PCM_FORMAT_FLOAT64_LE,
• [VIRTIO_SND_PCM_FMT_DSD_U8] = SNDRV_PCM_FORMAT_DSD_U8,
• [VIRTIO_SND_PCM_FMT_DSD_U16] = SNDRV_PCM_FORMAT_DSD_U16_LE,
• [VIRTIO_SND_PCM_FMT_DSD_U32] = SNDRV_PCM_FORMAT_DSD_U32_LE,
• [VIRTIO_SND_PCM_FMT_IEC958_SUBFRAME] =

• SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE
  

+};

+/* Map for converting VirtIO frame rate to ALSA frame rate. */ +struct virtsnd_v2a_rate {

• unsigned int alsa_bit;
• unsigned int rate;

+};

+static const struct virtsnd_v2a_rate g_v2a_rate_map[] = {

• [VIRTIO_SND_PCM_RATE_5512] = { SNDRV_PCM_RATE_5512, 5512 },
• [VIRTIO_SND_PCM_RATE_8000] = { SNDRV_PCM_RATE_8000, 8000 },
• [VIRTIO_SND_PCM_RATE_11025] = { SNDRV_PCM_RATE_11025, 11025 },
• [VIRTIO_SND_PCM_RATE_16000] = { SNDRV_PCM_RATE_16000, 16000 },
• [VIRTIO_SND_PCM_RATE_22050] = { SNDRV_PCM_RATE_22050, 22050 },
• [VIRTIO_SND_PCM_RATE_32000] = { SNDRV_PCM_RATE_32000, 32000 },
• [VIRTIO_SND_PCM_RATE_44100] = { SNDRV_PCM_RATE_44100, 44100 },
• [VIRTIO_SND_PCM_RATE_48000] = { SNDRV_PCM_RATE_48000, 48000 },
• [VIRTIO_SND_PCM_RATE_64000] = { SNDRV_PCM_RATE_64000, 64000 },
• [VIRTIO_SND_PCM_RATE_88200] = { SNDRV_PCM_RATE_88200, 88200 },
• [VIRTIO_SND_PCM_RATE_96000] = { SNDRV_PCM_RATE_96000, 96000 },
• [VIRTIO_SND_PCM_RATE_176400] = { SNDRV_PCM_RATE_176400, 176400 },
• [VIRTIO_SND_PCM_RATE_192000] = { SNDRV_PCM_RATE_192000, 192000 }

+};

+/**

• • virtsnd_pcm_build_hw() - Parse substream config and build HW descriptor.
• • @substream: VirtIO substream.
• • @info: VirtIO substream information entry.
• • Context: Any context.
• • Return: 0 on success, -EINVAL if configuration is invalid.
• */

+static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *substream,

• 		struct virtio_snd_pcm_info *info)
  

+{

• struct virtio_device *vdev = substream->snd->vdev;
• unsigned int i;
• u64 values;
• size_t sample_max = 0;
• size_t sample_min = 0;
• substream->features = le32_to_cpu(info->features);
• /*

• * TODO: set SNDRV_PCM_INFO_{BATCH,BLOCK_TRANSFER} if device supports
  

• * only message-based transport.
  

• */
  

• substream->hw.info =

• SNDRV_PCM_INFO_MMAP |
  

• SNDRV_PCM_INFO_MMAP_VALID |
  

• SNDRV_PCM_INFO_BATCH |
  

• SNDRV_PCM_INFO_BLOCK_TRANSFER |
  

• SNDRV_PCM_INFO_INTERLEAVED;
  

• if (!info->channels_min || info->channels_min > info->channels_max) {

• dev_err(&vdev->dev,
  

• 	"SID %u: invalid channel range [%u %u]\n",
  

• 	substream->sid, info->channels_min, info->channels_max);
  

• return -EINVAL;
  

• }
• substream->hw.channels_min = info->channels_min;
• substream->hw.channels_max = info->channels_max;
• values = le64_to_cpu(info->formats);
• substream->hw.formats = 0;
• for (i = 0; i < ARRAY_SIZE(g_v2a_format_map); ++i)

• if (values & (1ULL << i)) {
  

• 	unsigned int alsa_fmt = g_v2a_format_map[i];
  

• 	int bytes = snd_pcm_format_physical_width(alsa_fmt) / 8;
  

• 	if (!sample_min || sample_min > bytes)
  

• 		sample_min = bytes;
  

• 	if (sample_max < bytes)
  

• 		sample_max = bytes;
  

• 	substream->hw.formats |= (1ULL << alsa_fmt);
  

• }
  

• if (!substream->hw.formats) {

• dev_err(&vdev->dev,
  

• 	"SID %u: no supported PCM sample formats found\n",
  

• 	substream->sid);
  

• return -EINVAL;
  

• }
• values = le64_to_cpu(info->rates);
• substream->hw.rates = 0;
• for (i = 0; i < ARRAY_SIZE(g_v2a_rate_map); ++i)

• if (values & (1ULL << i)) {
  

• 	if (!substream->hw.rate_min ||
  

• 	    substream->hw.rate_min > g_v2a_rate_map[i].rate)
  

• 		substream->hw.rate_min = g_v2a_rate_map[i].rate;
  

• 	if (substream->hw.rate_max < g_v2a_rate_map[i].rate)
  

• 		substream->hw.rate_max = g_v2a_rate_map[i].rate;
  

• 	substream->hw.rates |= g_v2a_rate_map[i].alsa_bit;
  

• }
  

• if (!substream->hw.rates) {

• dev_err(&vdev->dev,
  

• 	"SID %u: no supported PCM frame rates found\n",
  

• 	substream->sid);
  

• return -EINVAL;
  

• }
• substream->hw.periods_min = pcm_periods_min;
• substream->hw.periods_max = pcm_periods_max;
• /*

• * We must ensure that there is enough space in the buffer to store
  

• * pcm_buffer_ms ms for the combination (Cmax, Smax, Rmax), where:
  

• *   Cmax = maximum supported number of channels,
  

• *   Smax = maximum supported sample size in bytes,
  

• *   Rmax = maximum supported frame rate.
  

• */
  

• substream->hw.buffer_bytes_max =

• sample_max * substream->hw.channels_max * pcm_buffer_ms *
  

• (substream->hw.rate_max / MSEC_PER_SEC);
  

• /* Align the buffer size to the page size */
• substream->hw.buffer_bytes_max =

• (substream->hw.buffer_bytes_max + PAGE_SIZE - 1) & -PAGE_SIZE;
  

• /*

• * We must ensure that the minimum period size is enough to store
  

• * pcm_period_ms_min ms for the combination (Cmin, Smin, Rmin), where:
  

• *   Cmin = minimum supported number of channels,
  

• *   Smin = minimum supported sample size in bytes,
  

• *   Rmin = minimum supported frame rate.
  

• */
  

• substream->hw.period_bytes_min =

• sample_min * substream->hw.channels_min * pcm_period_ms_min *
  

• (substream->hw.rate_min / MSEC_PER_SEC);
  

• /*

• * We must ensure that the maximum period size is enough to store
  

• * pcm_period_ms_max ms for the combination (Cmax, Smax, Rmax).
  

• */
  

• substream->hw.period_bytes_max =

• sample_max * substream->hw.channels_max * pcm_period_ms_max *
  

• (substream->hw.rate_max / MSEC_PER_SEC);
  

• return 0;

+}

+/**

• • virtsnd_pcm_prealloc_pages() - Preallocate substream hardware buffer.
• • @substream: VirtIO substream.
• • Context: Any context that permits to sleep.
• • Return: 0 on success, -errno on failure.
• */

+static int virtsnd_pcm_prealloc_pages(struct virtio_pcm_substream *substream) +{

• struct snd_pcm_substream *ksubstream = substream->substream;
• size_t size = substream->hw.buffer_bytes_max;
• struct device *data = snd_dma_continuous_data(GFP_KERNEL);
• /*

• * We just allocate a CONTINUOUS buffer as it should work in any setup.
  

• *
  

• * If there is a need to use DEV(_XXX), then add this case here and
  

• * (probably) update the related source code in other places.
  

• */
  

• snd_pcm_lib_preallocate_pages(ksubstream, SNDRV_DMA_TYPE_CONTINUOUS,

• 		      data, size, size);
  

• return 0;

looks like it can be void.

+}

+/**

• • virtsnd_pcm_find() - Find the PCM device for the specified node ID.
• • @snd: VirtIO sound device.
• • @nid: Function node ID.
• • Context: Any context.
• • Return: a pointer to the PCM device or ERR_PTR(-ENOENT).
• */

+struct virtio_pcm *virtsnd_pcm_find(struct virtio_snd *snd, unsigned int nid) +{

• struct virtio_pcm *pcm;
• list_for_each_entry(pcm, &snd->pcm_list, list)

• if (pcm->nid == nid)
  

• 	return pcm;
  

• return ERR_PTR(-ENOENT);

+}

+/**

• • virtsnd_pcm_find_or_create() - Find or create the PCM device for the

• •                            specified node ID.
    

• • @snd: VirtIO sound device.
• • @nid: Function node ID.
• • Context: Any context that permits to sleep.
• • Return: a pointer to the PCM device or ERR_PTR(-errno).
• */

+struct virtio_pcm *virtsnd_pcm_find_or_create(struct virtio_snd *snd,

• 			      unsigned int nid)
  

+{

• struct virtio_device *vdev = snd->vdev;
• struct virtio_pcm *pcm;
• pcm = virtsnd_pcm_find(snd, nid);
• if (!IS_ERR(pcm))

• return pcm;
  

• pcm = devm_kzalloc(&vdev->dev, sizeof(*pcm), GFP_KERNEL);
• if (!pcm)

• return ERR_PTR(-ENOMEM);
  

• pcm->nid = nid;
• list_add_tail(&pcm->list, &snd->pcm_list);
• return pcm;

+}

+/**

• • virtsnd_pcm_validate() - Validate if the device can be started.
• • @vdev: VirtIO parent device.
• • Context: Any context.
• • Return: 0 on success, -EINVAL on failure.
• */

+int virtsnd_pcm_validate(struct virtio_device *vdev) +{

• if (pcm_periods_min < 2 || pcm_periods_min > pcm_periods_max) {

• dev_err(&vdev->dev,
  

• 	"invalid range [%u %u] of the number of PCM periods\n",
  

• 	pcm_periods_min, pcm_periods_max);
  

• return -EINVAL;
  

• }
• if (!pcm_period_ms_min || pcm_period_ms_min > pcm_period_ms_max) {

• dev_err(&vdev->dev,
  

• 	"invalid range [%u %u] of the size of the PCM period\n",
  

• 	pcm_period_ms_min, pcm_period_ms_max);
  

• return -EINVAL;
  

• }
• if (pcm_buffer_ms < pcm_periods_min * pcm_period_ms_min) {

• dev_err(&vdev->dev,
  

• 	"pcm_buffer_ms(=%u) value cannot be < %u ms\n",
  

• 	pcm_buffer_ms, pcm_periods_min * pcm_period_ms_min);
  

• return -EINVAL;
  

• }
• if (pcm_period_ms_max > pcm_buffer_ms / 2) {

• dev_err(&vdev->dev,
  

• 	"pcm_period_ms_max(=%u) value cannot be > %u ms\n",
  

• 	pcm_period_ms_max, pcm_buffer_ms / 2);
  

• return -EINVAL;
  

• }
• return 0;

+}

+/**

• • virtsnd_pcm_parse_cfg() - Parse the stream configuration.
• • @snd: VirtIO sound device.
• • This function is called during initial device initialization.
• • Context: Any context that permits to sleep.
• • Return: 0 on success, -errno on failure.
• */

+int virtsnd_pcm_parse_cfg(struct virtio_snd *snd) +{

• struct virtio_device *vdev = snd->vdev;
• struct virtio_snd_pcm_info *info;
• unsigned int i;
• int rc;
• virtio_cread(vdev, struct virtio_snd_config, streams,

•      &snd->nsubstreams);
  

• if (!snd->nsubstreams)

• return 0;
  

• snd->substreams = devm_kcalloc(&vdev->dev, snd->nsubstreams,

• 		       sizeof(*snd->substreams), GFP_KERNEL);
  

• if (!snd->substreams)

• return -ENOMEM;
  

• info = devm_kcalloc(&vdev->dev, snd->nsubstreams, sizeof(*info),

• 	    GFP_KERNEL);
  

Just kmalloc() but make sure to free it in error cases below.

• if (!info)

• return -ENOMEM;
  

• rc = virtsnd_ctl_query_info(snd, VIRTIO_SND_R_PCM_INFO, 0,

• 		    snd->nsubstreams, sizeof(*info), info);
  

• if (rc)

• return rc;
  

• for (i = 0; i < snd->nsubstreams; ++i) {

• struct virtio_pcm_substream *substream = &snd->substreams[i];
  

• struct virtio_pcm *pcm;
  

• substream->snd = snd;
  

• substream->sid = i;
  

• rc = virtsnd_pcm_build_hw(substream, &info[i]);
  

• if (rc)
  

• 	return rc;
  

• substream->nid = le32_to_cpu(info[i].hdr.hda_fn_nid);
  

• pcm = virtsnd_pcm_find_or_create(snd, substream->nid);
  

• if (IS_ERR(pcm))
  

• 	return PTR_ERR(pcm);
  

• switch (info[i].direction) {
  

• case VIRTIO_SND_D_OUTPUT: {
  

Same comment about braces and in other cases in the series.

• 	substream->direction = SNDRV_PCM_STREAM_PLAYBACK;
  

• 	break;
  

• }
  

• case VIRTIO_SND_D_INPUT: {
  

• 	substream->direction = SNDRV_PCM_STREAM_CAPTURE;
  

• 	break;
  

• }
  

• default: {
  

• 	dev_err(&vdev->dev, "SID %u: unknown direction (%u)\n",
  

• 		substream->sid, info[i].direction);
  

• 	return -EINVAL;
  

• }
  

• }
  

• pcm->streams[substream->direction].nsubstreams++;
  

• }
• devm_kfree(&vdev->dev, info);
• return 0;

+}

+/**

• • virtsnd_pcm_build_devs() - Build ALSA PCM devices.
• • @snd: VirtIO sound device.
• • Context: Any context that permits to sleep.
• • Return: 0 on success, -errno on failure.
• */

+int virtsnd_pcm_build_devs(struct virtio_snd *snd) +{

• struct virtio_device *vdev = snd->vdev;
• struct virtio_pcm *pcm;
• unsigned int i;
• int rc;
• list_for_each_entry(pcm, &snd->pcm_list, list) {

• unsigned int npbs =
  

• 	pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].nsubstreams;
  

• unsigned int ncps =
  

• 	pcm->streams[SNDRV_PCM_STREAM_CAPTURE].nsubstreams;
  

• if (!npbs && !ncps)
  

• 	continue;
  

• rc = snd_pcm_new(snd->card, "virtio_snd", pcm->nid, npbs, ncps,
  

• 		 &pcm->pcm);
  

• if (rc) {
  

• 	dev_err(&vdev->dev, "snd_pcm_new[%u] failed: %d\n",
  

• 		pcm->nid, rc);
  

• 	return rc;
  

• }
  

• pcm->pcm->info_flags = 0;
  

• pcm->pcm->dev_class = SNDRV_PCM_CLASS_GENERIC;
  

• pcm->pcm->dev_subclass = SNDRV_PCM_SUBCLASS_GENERIC_MIX;
  

• strscpy(pcm->pcm->name, "VirtIO PCM", sizeof(pcm->pcm->name));
  

• pcm->pcm->private_data = pcm;
  

• for (i = 0; i < ARRAY_SIZE(pcm->streams); ++i) {
  

• 	struct virtio_pcm_stream *stream = &pcm->streams[i];
  

• 	if (!stream->nsubstreams)
  

• 		continue;
  

• 	stream->substreams =
  

• 		devm_kcalloc(&vdev->dev,
  

• 			     stream->nsubstreams,
  

• 			     sizeof(*stream->substreams),
  

• 			     GFP_KERNEL);
  

• 	if (!stream->substreams)
  

• 		return -ENOMEM;
  

• 	stream->nsubstreams = 0;
  

• }
  

• }
• for (i = 0; i < snd->nsubstreams; ++i) {

• struct virtio_pcm_substream *substream = &snd->substreams[i];
  

• struct virtio_pcm_stream *stream;
  

• pcm = virtsnd_pcm_find(snd, substream->nid);
  

• if (IS_ERR(pcm))
  

• 	return PTR_ERR(pcm);
  

• stream = &pcm->streams[substream->direction];
  

• stream->substreams[stream->nsubstreams++] = substream;
  

• }
• list_for_each_entry(pcm, &snd->pcm_list, list)

• for (i = 0; i < ARRAY_SIZE(pcm->streams); ++i) {
  

• 	struct virtio_pcm_stream *stream = &pcm->streams[i];
  

• 	struct snd_pcm_str *kstream;
  

• 	struct snd_pcm_substream *ksubstream;
  

• 	if (!stream->nsubstreams)
  

• 		continue;
  

• 	kstream = &pcm->pcm->streams[i];
  

• 	ksubstream = kstream->substream;
  

• 	while (ksubstream) {
  

cosmetic: this could be

for (substream = kstream->substream; ksubstream; ksubstream = ksubstream->next)

• 		struct virtio_pcm_substream *substream =
  

• 			stream->substreams[ksubstream->number];
  

• 		substream->substream = ksubstream;
  

• 		ksubstream = ksubstream->next;
  

• 		rc = virtsnd_pcm_prealloc_pages(substream);
  

• 		if (rc)
  

• 			return rc;
  

• 	}
  

• }
  

• return 0;

+}

+/**

• • virtsnd_pcm_event() - Handle the PCM device event notification.
• • @snd: VirtIO sound device.
• • @event: VirtIO sound event.
• • Context: Interrupt context.
• */

+void virtsnd_pcm_event(struct virtio_snd *snd, struct virtio_snd_event *event) +{

• struct virtio_pcm_substream *substream;
• unsigned int sid = le32_to_cpu(event->data);
• if (sid >= snd->nsubstreams)

• return;
  

• substream = &snd->substreams[sid];
• switch (le32_to_cpu(event->hdr.code)) {
• case VIRTIO_SND_EVT_PCM_PERIOD_ELAPSED: {

• /* TODO: deal with shmem elapsed period */
  

• break;
  

• }
• case VIRTIO_SND_EVT_PCM_XRUN: {

• break;
  

• }
• }

+}

Thanks Guennadi