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Subject: Re: [PATCH 3/7] ALSA: virtio: add virtio sound driver
To:     "Michael S. Tsirkin" <mst@redhat.com>
CC:     <virtualization@lists.linux-foundation.org>,
        <alsa-devel@alsa-project.org>, <virtio-dev@lists.oasis-open.org>,
        <linux-kernel@vger.kernel.org>, Takashi Iwai <tiwai@suse.com>
References: <20210120003638.3339987-1-anton.yakovlev@opensynergy.com>
 <20210120003638.3339987-4-anton.yakovlev@opensynergy.com>
 <20210120032319-mutt-send-email-mst@kernel.org>
From:   Anton Yakovlev <anton.yakovlev@opensynergy.com>
Message-ID: <7edef85d-b9d4-5ce7-cdd5-2b992f2f319f@opensynergy.com>
Date:   Sun, 24 Jan 2021 17:48:50 +0100
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On 20.01.2021 09:26, Michael S. Tsirkin wrote:
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> 
> 
> On Wed, Jan 20, 2021 at 01:36:31AM +0100, Anton Yakovlev wrote:
>> Introduce skeleton of the virtio sound driver. The driver implements
>> the virtio sound device specification, which has become part of the
>> virtio standard.
>>
>> Initial initialization of the device, virtqueues and creation of an
>> empty ALSA sound device. Also, handling DEVICE_NEEDS_RESET device
>> status.
>>
>> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
>> ---
>>   MAINTAINERS                   |   2 +
>>   sound/Kconfig                 |   2 +
>>   sound/Makefile                |   3 +-
>>   sound/virtio/Kconfig          |  10 +
>>   sound/virtio/Makefile         |   9 +
>>   sound/virtio/virtio_card.c    | 473 ++++++++++++++++++++++++++++++
>>   sound/virtio/virtio_card.h    |  92 ++++++
>>   sound/virtio/virtio_ctl_msg.c | 293 +++++++++++++++++++
>>   sound/virtio/virtio_ctl_msg.h | 122 ++++++++
>>   sound/virtio/virtio_pcm.c     | 536 ++++++++++++++++++++++++++++++++++
>>   sound/virtio/virtio_pcm.h     |  89 ++++++
>>   11 files changed, 1630 insertions(+), 1 deletion(-)
>>   create mode 100644 sound/virtio/Kconfig
>>   create mode 100644 sound/virtio/Makefile
>>   create mode 100644 sound/virtio/virtio_card.c
>>   create mode 100644 sound/virtio/virtio_card.h
>>   create mode 100644 sound/virtio/virtio_ctl_msg.c
>>   create mode 100644 sound/virtio/virtio_ctl_msg.h
>>   create mode 100644 sound/virtio/virtio_pcm.c
>>   create mode 100644 sound/virtio/virtio_pcm.h
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 6dfd59eafe82..8a0e9f04402f 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -18939,8 +18939,10 @@ F:   include/uapi/linux/virtio_mem.h
>>   VIRTIO SOUND DRIVER
>>   M:   Anton Yakovlev <anton.yakovlev@opensynergy.com>
>>   L:   virtualization@lists.linux-foundation.org
>> +L:   alsa-devel@alsa-project.org (moderated for non-subscribers)
>>   S:   Maintained
>>   F:   include/uapi/linux/virtio_snd.h
>> +F:   sound/virtio/*
>>
>>   VIRTUAL BOX GUEST DEVICE DRIVER
>>   M:   Hans de Goede <hdegoede@redhat.com>
>> diff --git a/sound/Kconfig b/sound/Kconfig
>> index 36785410fbe1..e56d96d2b11c 100644
>> --- a/sound/Kconfig
>> +++ b/sound/Kconfig
>> @@ -99,6 +99,8 @@ source "sound/synth/Kconfig"
>>
>>   source "sound/xen/Kconfig"
>>
>> +source "sound/virtio/Kconfig"
>> +
>>   endif # SND
>>
>>   endif # !UML
>> diff --git a/sound/Makefile b/sound/Makefile
>> index 797ecdcd35e2..04ef04b1168f 100644
>> --- a/sound/Makefile
>> +++ b/sound/Makefile
>> @@ -5,7 +5,8 @@
>>   obj-$(CONFIG_SOUND) += soundcore.o
>>   obj-$(CONFIG_DMASOUND) += oss/dmasound/
>>   obj-$(CONFIG_SND) += core/ i2c/ drivers/ isa/ pci/ ppc/ arm/ sh/ synth/ usb/ \
>> -     firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/ xen/
>> +     firewire/ sparc/ spi/ parisc/ pcmcia/ mips/ soc/ atmel/ hda/ x86/ xen/ \
>> +     virtio/
>>   obj-$(CONFIG_SND_AOA) += aoa/
>>
>>   # This one must be compilable even if sound is configured out
>> diff --git a/sound/virtio/Kconfig b/sound/virtio/Kconfig
>> new file mode 100644
>> index 000000000000..094cba24ee5b
>> --- /dev/null
>> +++ b/sound/virtio/Kconfig
>> @@ -0,0 +1,10 @@
>> +# SPDX-License-Identifier: GPL-2.0+
>> +# Sound card driver for virtio
>> +
>> +config SND_VIRTIO
>> +     tristate "Virtio sound driver"
>> +     depends on VIRTIO
>> +     select SND_PCM
>> +     select SND_JACK
>> +     help
>> +          This is the virtual sound driver for virtio. Say Y or M.
>> diff --git a/sound/virtio/Makefile b/sound/virtio/Makefile
>> new file mode 100644
>> index 000000000000..69162a545a41
>> --- /dev/null
>> +++ b/sound/virtio/Makefile
>> @@ -0,0 +1,9 @@
>> +# SPDX-License-Identifier: GPL-2.0+
>> +
>> +obj-$(CONFIG_SND_VIRTIO) += virtio_snd.o
>> +
>> +virtio_snd-objs := \
>> +     virtio_card.o \
>> +     virtio_ctl_msg.o \
>> +     virtio_pcm.o
>> +
>> diff --git a/sound/virtio/virtio_card.c b/sound/virtio/virtio_card.c
>> new file mode 100644
>> index 000000000000..293d497f24e7
>> --- /dev/null
>> +++ b/sound/virtio/virtio_card.c
>> @@ -0,0 +1,473 @@
>> +// 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/module.h>
>> +#include <linux/moduleparam.h>
>> +#include <linux/virtio_config.h>
>> +#include <sound/initval.h>
>> +#include <uapi/linux/virtio_ids.h>
>> +
>> +#include "virtio_card.h"
>> +
>> +int msg_timeout_ms = MSEC_PER_SEC;
>> +module_param(msg_timeout_ms, int, 0644);
>> +MODULE_PARM_DESC(msg_timeout_ms, "Message completion timeout in milliseconds");
>> +
>> +static int virtsnd_probe(struct virtio_device *vdev);
>> +static void virtsnd_remove(struct virtio_device *vdev);
>> +
>> +/**
>> + * virtsnd_event_send() - Add an event to the event queue.
>> + * @vqueue: Underlying event virtqueue.
>> + * @event: Event.
>> + * @notify: Indicates whether or not to send a notification to the device.
>> + * @gfp: Kernel flags for memory allocation.
>> + *
>> + * Context: Any context.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_event_send(struct virtqueue *vqueue,
>> +                           struct virtio_snd_event *event, bool notify,
>> +                           gfp_t gfp)
>> +{
>> +     struct scatterlist sg;
>> +     struct scatterlist *psgs[1] = { &sg };
>> +     int rc;
>> +
>> +     /* reset event content */
>> +     memset(event, 0, sizeof(*event));
>> +
>> +     sg_init_one(&sg, event, sizeof(*event));
>> +
>> +     rc = virtqueue_add_sgs(vqueue, psgs, 0, 1, event, gfp);
>> +     if (rc)
>> +             return rc;
>> +
>> +     if (notify)
>> +             if (virtqueue_kick_prepare(vqueue))
>> +                     if (!virtqueue_notify(vqueue))
>> +                             return -EIO;
>> +
>> +     return 0;
>> +}
>> +
>> +/**
>> + * virtsnd_event_notify_cb() - Dispatch all reported events from the event queue.
>> + * @vqueue: Underlying event virtqueue.
>> + *
>> + * This callback function is called upon a vring interrupt request from the
>> + * device.
>> + *
>> + * Context: Interrupt context.
>> + */
>> +static void virtsnd_event_notify_cb(struct virtqueue *vqueue)
>> +{
>> +     struct virtio_snd *snd = vqueue->vdev->priv;
>> +     struct virtio_snd_queue *queue = virtsnd_event_queue(snd);
>> +     unsigned long flags;
>> +
>> +     spin_lock_irqsave(&queue->lock, flags);
>> +     while (queue->vqueue) {
>> +             virtqueue_disable_cb(queue->vqueue);
>> +
>> +             for (;;) {
>> +                     struct virtio_snd_event *event;
>> +                     u32 length;
>> +
>> +                     event = virtqueue_get_buf(queue->vqueue, &length);
>> +                     if (!event)
>> +                             break;
>> +
>> +                     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);
>> +                             break;
>> +                     }
>> +                     default: {
>> +                             break;
>> +                     }
>> +                     }
>> +
>> +                     virtsnd_event_send(queue->vqueue, event, true,
>> +                                        GFP_ATOMIC);
>> +             }
>> +
>> +             if (unlikely(virtqueue_is_broken(queue->vqueue)))
>> +                     break;
>> +
>> +             if (virtqueue_enable_cb(queue->vqueue))
>> +                     break;
>> +     }
>> +     spin_unlock_irqrestore(&queue->lock, flags);
>> +}
>> +
>> +/**
>> + * virtsnd_find_vqs() - Enumerate and initialize all virtqueues.
>> + * @snd: VirtIO sound device.
>> + *
>> + * After calling this function, interrupts are allowed only for the control
>> + * queue, all other queues are disabled.
>> + *
>> + * Context: Any context.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_find_vqs(struct virtio_snd *snd)
>> +{
>> +     struct virtio_device *vdev = snd->vdev;
>> +     vq_callback_t *callbacks[VIRTIO_SND_VQ_MAX] = { 0 };
>> +     const char *names[VIRTIO_SND_VQ_MAX] = {
>> +             [VIRTIO_SND_VQ_CONTROL] = "virtsnd-ctl",
>> +             [VIRTIO_SND_VQ_EVENT] = "virtsnd-event",
>> +             [VIRTIO_SND_VQ_TX] = "virtsnd-tx",
>> +             [VIRTIO_SND_VQ_RX] = "virtsnd-rx"
>> +     };
>> +     struct virtqueue *vqs[VIRTIO_SND_VQ_MAX] = { 0 };
>> +     unsigned int i;
>> +     unsigned int n = 0;
>> +     int rc;
>> +
>> +     callbacks[VIRTIO_SND_VQ_CONTROL] = virtsnd_ctl_notify_cb;
>> +     callbacks[VIRTIO_SND_VQ_EVENT] = virtsnd_event_notify_cb;
>> +
>> +     rc = virtio_find_vqs(vdev, VIRTIO_SND_VQ_MAX, vqs, callbacks, names,
>> +                          NULL);
>> +     if (rc) {
>> +             dev_err(&vdev->dev, "failed to initialize virtqueues\n");
>> +             return rc;
>> +     }
>> +
>> +     for (i = 0; i < VIRTIO_SND_VQ_MAX; ++i) {
>> +             /*
>> +              * By default, disable callbacks for all queues except the
>> +              * control queue, since the device must be fully initialized
>> +              * first.
>> +              */
>> +             if (i != VIRTIO_SND_VQ_CONTROL)
>> +                     virtqueue_disable_cb(vqs[i]);
>> +
>> +             snd->queues[i].vqueue = vqs[i];
>> +     }
>> +
>> +     /* Allocate events and populate the event queue */
>> +     n = virtqueue_get_vring_size(vqs[VIRTIO_SND_VQ_EVENT]);
>> +
>> +     snd->event_msgs = devm_kcalloc(&vdev->dev, n, sizeof(*snd->event_msgs),
>> +                                    GFP_KERNEL);
>> +     if (!snd->event_msgs)
>> +             return -ENOMEM;
>> +
>> +     for (i = 0; i < n; ++i) {
>> +             rc = virtsnd_event_send(vqs[VIRTIO_SND_VQ_EVENT],
>> +                                     &snd->event_msgs[i], false, GFP_KERNEL);
>> +             if (rc)
>> +                     return rc;
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +/**
>> + * virtsnd_enable_vqs() - Enable the event, tx and rx virtqueues.
>> + * @snd: VirtIO sound device.
>> + *
>> + * Context: Any context.
>> + */
>> +static void virtsnd_enable_vqs(struct virtio_snd *snd)
>> +{
>> +     struct virtqueue *vqueue;
>> +
>> +     vqueue = snd->queues[VIRTIO_SND_VQ_EVENT].vqueue;
>> +     if (!virtqueue_enable_cb(vqueue))
>> +             virtsnd_event_notify_cb(vqueue);
>> +}
>> +
>> +/**
>> + * virtsnd_disable_vqs() - Disable all virtqueues.
>> + * @snd: VirtIO sound device.
>> + *
>> + * Also free all allocated events and control messages.
>> + *
>> + * Context: Any context.
>> + */
>> +static void virtsnd_disable_vqs(struct virtio_snd *snd)
>> +{
>> +     struct virtio_device *vdev = snd->vdev;
>> +     unsigned int i;
>> +     unsigned long flags;
>> +
>> +     for (i = 0; i < VIRTIO_SND_VQ_MAX; ++i) {
>> +             struct virtio_snd_queue *queue = &snd->queues[i];
>> +
>> +             spin_lock_irqsave(&queue->lock, flags);
>> +             /* Prohibit the use of the queue */
>> +             if (queue->vqueue)
>> +                     virtqueue_disable_cb(queue->vqueue);
>> +             queue->vqueue = NULL;
>> +             /* Cancel all pending requests for the control queue */
>> +             if (i == VIRTIO_SND_VQ_CONTROL) {
>> +                     struct virtio_snd_msg *msg;
>> +                     struct virtio_snd_msg *next;
>> +
>> +                     list_for_each_entry_safe(msg, next, &snd->ctl_msgs,
>> +                                              list)
>> +                             virtsnd_ctl_msg_complete(snd, msg);
>> +             }
>> +             spin_unlock_irqrestore(&queue->lock, flags);
>> +     }
>> +
>> +     if (snd->event_msgs)
>> +             devm_kfree(&vdev->dev, snd->event_msgs);
>> +
>> +     snd->event_msgs = NULL;
>> +}
>> +
>> +/**
>> + * virtsnd_reset_fn() - Kernel worker's function to reset the device.
>> + * @work: Reset device work.
>> + *
>> + * Context: Process context.
>> + */
>> +static void virtsnd_reset_fn(struct work_struct *work)
>> +{
>> +     struct virtio_snd *snd =
>> +             container_of(work, struct virtio_snd, reset_work);
>> +     struct virtio_device *vdev = snd->vdev;
>> +     struct device *dev = &vdev->dev;
>> +     int rc;
>> +
>> +     dev_info(dev, "sound device needs reset\n");
>> +
>> +     /*
>> +      * It seems that the only way to properly reset the device is to remove
>> +      * and re-create the ALSA sound card device.
>> +      */
>> +     virtsnd_remove(vdev);
>> +
>> +     rc = virtsnd_probe(vdev);
>> +     if (rc)
>> +             dev_err(dev, "re-probe() failed: %d\n", rc);
>> +}
>> +
>> +/**
>> + * virtsnd_build_devs() - Read configuration and build ALSA devices.
>> + * @snd: VirtIO sound device.
>> + *
>> + * Context: Any context that permits to sleep.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_build_devs(struct virtio_snd *snd)
>> +{
>> +     struct virtio_device *vdev = snd->vdev;
>> +     int rc;
>> +
>> +     rc = snd_card_new(&vdev->dev, SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1,
>> +                       THIS_MODULE, 0, &snd->card);
>> +     if (rc < 0)
>> +             return rc;
>> +
>> +     snd->card->private_data = snd;
>> +
>> +     strscpy(snd->card->id, "viosnd", sizeof(snd->card->id));
>> +     strscpy(snd->card->driver, "virtio_snd", sizeof(snd->card->driver));
>> +     strscpy(snd->card->shortname, "VIOSND", sizeof(snd->card->shortname));
>> +     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);
>> +}
>> +
>> +/**
>> + * virtsnd_validate() - Validate if the device can be started.
>> + * @vdev: VirtIO parent device.
>> + *
>> + * Context: Any context.
>> + * Return: 0 on success, -EINVAL on failure.
>> + */
>> +static int virtsnd_validate(struct virtio_device *vdev)
>> +{
>> +     if (!vdev->config->get) {
>> +             dev_err(&vdev->dev, "configuration access disabled\n");
>> +             return -EINVAL;
>> +     }
>> +
>> +     if (!msg_timeout_ms) {
>> +             dev_err(&vdev->dev, "msg_timeout_ms value cannot be zero\n");
>> +             return -EINVAL;
>> +     }
>> +
>> +     if (virtsnd_pcm_validate(vdev))
>> +             return -EINVAL;
>> +
> 
> I think you also need VIRTIO_F_VERSION_1.

Added additional check in v2.


>> +     return 0;
>> +}
>> +
>> +/**
>> + * virtsnd_probe() - Create and initialize the device.
>> + * @vdev: VirtIO parent device.
>> + *
>> + * Context: Any context that permits to sleep.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +static int virtsnd_probe(struct virtio_device *vdev)
>> +{
>> +     struct virtio_snd *snd;
>> +     unsigned int i;
>> +     int rc;
>> +
>> +     snd = devm_kzalloc(&vdev->dev, sizeof(*snd), GFP_KERNEL);
>> +     if (!snd)
>> +             return -ENOMEM;
>> +
>> +     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;
>> +
>> +     for (i = 0; i < VIRTIO_SND_VQ_MAX; ++i)
>> +             spin_lock_init(&snd->queues[i].lock);
>> +
>> +     rc = virtsnd_find_vqs(snd);
>> +     if (rc)
>> +             goto on_failure;
>> +
>> +     virtio_device_ready(vdev);
>> +
>> +     rc = virtsnd_build_devs(snd);
>> +     if (rc)
>> +             goto on_failure;
>> +
>> +     virtsnd_enable_vqs(snd);
> 
> 
> Shouldn't virtsnd_enable_vqs happen first?
> Looks like after virtsnd_build_devs Linux can already
> try to make noise ...

Since only the event virtqueue must be disabled before calling
virtsnd_build_devs, I've simplified the code here in v2. The other three
virtqueues are now always enabled.


>> +
>> +on_failure:
>> +     if (rc)
>> +             virtsnd_remove(vdev);
>> +
>> +     return rc;
>> +}
>> +
>> +/**
>> + * virtsnd_remove() - Remove VirtIO and ALSA devices.
>> + * @vdev: VirtIO parent device.
>> + *
>> + * Context: Any context that permits to sleep.
>> + */
>> +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;
>> +
>> +     virtsnd_disable_vqs(snd);
> 
> Here Linux can still try to use the device, so all
> the cleanup we are doing is too early?

We can get here also because of the DEVICE_NEEDS_RESET status. In this
case, there may be pending synchronous control requests. This means that
a subsequent call to snd_card_free may take a significant amount of time
(until the message timed out). So it is best to disable the virtqueues
and cancel any pending messages first.

By the way, could you take a look into the reset worker function in v2:
   [2/9] virtio_card.c:virtsnd_reset_fn()
I put there additional comments. The question is, is the current
solution acceptable? The code itself works fine though.


>> +
>> +     if (snd->card)
>> +             snd_card_free(snd->card);
>> +
>> +     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);
>> +     }
>> +
>> +     if (snd->substreams)
>> +             devm_kfree(&vdev->dev, snd->substreams);
>> +
>> +     devm_kfree(&vdev->dev, snd);
>> +
>> +     vdev->priv = NULL;
>> +}
>> +
>> +/**
>> + * virtsnd_config_changed() - Handle configuration change notification.
>> + * @vdev: VirtIO parent device.
>> + *
>> + * This callback function is called upon a configuration change interrupt
>> + * request from the device. Currently only used to handle NEEDS_RESET device
>> + * status.
>> + *
>> + * Context: Interrupt context.
>> + */
>> +static void virtsnd_config_changed(struct virtio_device *vdev)
>> +{
>> +     struct virtio_snd *snd = vdev->priv;
>> +     unsigned int status = vdev->config->get_status(vdev);
>> +
>> +     if (status & VIRTIO_CONFIG_S_NEEDS_RESET)
>> +             schedule_work(&snd->reset_work);
>> +     else
>> +             dev_warn(&vdev->dev,
>> +                      "sound device configuration was changed\n");
>> +}
>> +
>> +static const struct virtio_device_id id_table[] = {
>> +     { VIRTIO_ID_SOUND, VIRTIO_DEV_ANY_ID },
>> +     { 0 },
>> +};
>> +
>> +static struct virtio_driver virtsnd_driver = {
>> +     .driver.name = KBUILD_MODNAME,
>> +     .driver.owner = THIS_MODULE,
>> +     .id_table = id_table,
>> +     .validate = virtsnd_validate,
>> +     .probe = virtsnd_probe,
>> +     .remove = virtsnd_remove,
>> +     .config_changed = virtsnd_config_changed,
>> +};
>> +
>> +static int __init init(void)
>> +{
>> +     return register_virtio_driver(&virtsnd_driver);
>> +}
>> +module_init(init);
>> +
>> +static void __exit fini(void)
>> +{
>> +     unregister_virtio_driver(&virtsnd_driver);
>> +}
>> +module_exit(fini);
>> +
>> +MODULE_DEVICE_TABLE(virtio, id_table);
>> +MODULE_DESCRIPTION("Virtio sound card driver");
>> +MODULE_LICENSE("GPL");
>> diff --git a/sound/virtio/virtio_card.h b/sound/virtio/virtio_card.h
>> new file mode 100644
>> index 000000000000..be6651a6aaf8
>> --- /dev/null
>> +++ b/sound/virtio/virtio_card.h
>> @@ -0,0 +1,92 @@
>> +/* 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/>.
>> + */
>> +#ifndef VIRTIO_SND_CARD_H
>> +#define VIRTIO_SND_CARD_H
>> +
>> +#include <linux/virtio.h>
>> +#include <sound/core.h>
>> +#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.
>> + * @lock: Used to synchronize access to a virtqueue.
>> + * @vqueue: Underlying virtqueue.
>> + */
>> +struct virtio_snd_queue {
>> +     spinlock_t lock;
>> +     struct virtqueue *vqueue;
>> +};
>> +
>> +/**
>> + * struct virtio_snd - VirtIO sound card device.
>> + * @vdev: Underlying virtio device.
>> + * @queues: Virtqueue wrappers.
>> + * @reset_work: Reset device work.
>> + * @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;
>> +     struct virtio_snd_queue queues[VIRTIO_SND_VQ_MAX];
>> +     struct work_struct reset_work;
>> +     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). */
>> +extern int msg_timeout_ms;
>> +
>> +static inline struct virtio_snd_queue *
>> +virtsnd_control_queue(struct virtio_snd *snd)
>> +{
>> +     return &snd->queues[VIRTIO_SND_VQ_CONTROL];
>> +}
>> +
>> +static inline struct virtio_snd_queue *
>> +virtsnd_event_queue(struct virtio_snd *snd)
>> +{
>> +     return &snd->queues[VIRTIO_SND_VQ_EVENT];
>> +}
>> +
>> +static inline struct virtio_snd_queue *
>> +virtsnd_tx_queue(struct virtio_snd *snd)
>> +{
>> +     return &snd->queues[VIRTIO_SND_VQ_TX];
>> +}
>> +
>> +static inline struct virtio_snd_queue *
>> +virtsnd_rx_queue(struct virtio_snd *snd)
>> +{
>> +     return &snd->queues[VIRTIO_SND_VQ_RX];
>> +}
>> +
>> +#endif /* VIRTIO_SND_CARD_H */
>> diff --git a/sound/virtio/virtio_ctl_msg.c b/sound/virtio/virtio_ctl_msg.c
>> new file mode 100644
>> index 000000000000..c1701756bc32
>> --- /dev/null
>> +++ b/sound/virtio/virtio_ctl_msg.c
>> @@ -0,0 +1,293 @@
>> +// 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"
>> +#include "virtio_ctl_msg.h"
>> +
>> +/**
>> + * virtsnd_ctl_msg_alloc_ext() - Allocate and initialize a control message.
>> + * @vdev: VirtIO parent device.
>> + * @request_size: Size of request header (pointed to by sg_request field).
>> + * @response_size: Size of response header (pointed to by sg_response field).
>> + * @sgs: Additional data to attach to the message (may be NULL).
>> + * @out_sgs: Number of scattergather elements to attach to the request header.
>> + * @in_sgs: Number of scattergather elements to attach to the response header.
>> + * @gfp: Kernel flags for memory allocation.
>> + *
>> + * The message will be automatically freed when the ref_count value is 0.
>> + *
>> + * Context: Any context. May sleep if @gfp flags permit.
>> + * Return: Allocated message on success, ERR_PTR(-errno) on failure.
>> + */
>> +struct virtio_snd_msg *virtsnd_ctl_msg_alloc_ext(struct virtio_device *vdev,
>> +                                              size_t request_size,
>> +                                              size_t response_size,
>> +                                              struct scatterlist *sgs,
>> +                                              unsigned int out_sgs,
>> +                                              unsigned int in_sgs, gfp_t gfp)
>> +{
>> +     struct virtio_snd_msg *msg;
>> +     size_t msg_size =
>> +             sizeof(*msg) + (1 + out_sgs + 1 + in_sgs) * sizeof(*msg->sgs);
>> +     unsigned int i;
>> +
>> +     msg = devm_kzalloc(&vdev->dev, msg_size + request_size + response_size,
>> +                        gfp);
>> +     if (!msg)
>> +             return ERR_PTR(-ENOMEM);
>> +
>> +     sg_init_one(&msg->sg_request, (u8 *)msg + msg_size, request_size);
>> +     sg_init_one(&msg->sg_response, (u8 *)msg + msg_size + request_size,
>> +                 response_size);
>> +
>> +     INIT_LIST_HEAD(&msg->list);
>> +     init_completion(&msg->notify);
>> +     atomic_set(&msg->ref_count, 1);
>> +
>> +     msg->sgs[msg->out_sgs++] = &msg->sg_request;
>> +     if (sgs)
>> +             for (i = 0; i < out_sgs; ++i)
>> +                     msg->sgs[msg->out_sgs++] = &sgs[i];
>> +
>> +     msg->sgs[msg->out_sgs + msg->in_sgs++] = &msg->sg_response;
>> +     if (sgs)
>> +             for (i = out_sgs; i < out_sgs + in_sgs; ++i)
>> +                     msg->sgs[msg->out_sgs + msg->in_sgs++] = &sgs[i];
>> +
>> +     return msg;
>> +}
>> +
>> +/**
>> + * virtsnd_ctl_msg_send() - Send an (asynchronous) control message.
>> + * @snd: VirtIO sound device.
>> + * @msg: Control message.
>> + *
>> + * If a message is failed to be enqueued, it will be deleted. If message content
>> + * is still needed, the caller must additionally to virtsnd_ctl_msg_ref/unref()
>> + * it.
>> + *
>> + * Context: Any context. Takes and releases the control queue spinlock.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +int virtsnd_ctl_msg_send(struct virtio_snd *snd, struct virtio_snd_msg *msg)
>> +{
>> +     struct virtio_device *vdev = snd->vdev;
>> +     struct virtio_snd_queue *queue = virtsnd_control_queue(snd);
>> +     struct virtio_snd_hdr *response = sg_virt(&msg->sg_response);
>> +     bool notify = false;
>> +     unsigned long flags;
>> +     int rc = -EIO;
>> +
>> +     /* Set the default status in case the message was not sent or was
>> +      * canceled.
>> +      */
>> +     response->code = cpu_to_virtio32(vdev, VIRTIO_SND_S_IO_ERR);
>> +
>> +     spin_lock_irqsave(&queue->lock, flags);
>> +     if (queue->vqueue) {
>> +             rc = virtqueue_add_sgs(queue->vqueue, msg->sgs, msg->out_sgs,
>> +                                    msg->in_sgs, msg, GFP_ATOMIC);
>> +             if (!rc) {
>> +                     notify = virtqueue_kick_prepare(queue->vqueue);
>> +                     list_add_tail(&msg->list, &snd->ctl_msgs);
>> +             }
>> +     }
>> +     spin_unlock_irqrestore(&queue->lock, flags);
>> +
>> +     if (!rc) {
>> +             if (!notify || virtqueue_notify(queue->vqueue))
>> +                     return 0;
>> +
>> +             spin_lock_irqsave(&queue->lock, flags);
>> +             list_del(&msg->list);
>> +             spin_unlock_irqrestore(&queue->lock, flags);
>> +     }
>> +
>> +     virtsnd_ctl_msg_unref(snd->vdev, msg);
>> +
>> +     return -EIO;
>> +}
>> +
>> +/**
>> + * virtsnd_ctl_msg_send_sync() - Send a (synchronous) control message.
>> + * @snd: VirtIO sound device.
>> + * @msg: Control message.
>> + *
>> + * After returning from this function, the message will be deleted. If message
>> + * content is still needed, the caller must additionally to
>> + * virtsnd_ctl_msg_ref/unref() it.
>> + *
>> + * The msg_timeout_ms module parameter defines the message completion timeout.
>> + * If the message is not completed within this time, the function will return an
>> + * error.
>> + *
>> + * Context: Any context. Takes and releases the control queue spinlock.
>> + * Return: 0 on success, -errno on failure.
>> + *
>> + * The return value is a message status code (VIRTIO_SND_S_XXX) converted to an
>> + * appropriate -errno value.
>> + */
>> +int virtsnd_ctl_msg_send_sync(struct virtio_snd *snd,
>> +                           struct virtio_snd_msg *msg)
>> +{
>> +     struct virtio_device *vdev = snd->vdev;
>> +     unsigned int js = msecs_to_jiffies(msg_timeout_ms);
>> +     struct virtio_snd_hdr *response;
>> +     int rc;
>> +
>> +     virtsnd_ctl_msg_ref(vdev, msg);
>> +
>> +     rc = virtsnd_ctl_msg_send(snd, msg);
>> +     if (rc)
>> +             goto on_failure;
>> +
>> +     rc = wait_for_completion_interruptible_timeout(&msg->notify, js);
>> +     if (rc <= 0) {
>> +             if (!rc) {
>> +                     struct virtio_snd_hdr *request =
>> +                             sg_virt(&msg->sg_request);
>> +
>> +                     dev_err(&vdev->dev,
>> +                             "control message (0x%08x) timeout\n",
>> +                             le32_to_cpu(request->code));
>> +                     rc = -EIO;
>> +             }
>> +
>> +             goto on_failure;
>> +     }
>> +
>> +     response = sg_virt(&msg->sg_response);
>> +
>> +     switch (le32_to_cpu(response->code)) {
>> +     case VIRTIO_SND_S_OK:
>> +             rc = 0;
>> +             break;
>> +     case VIRTIO_SND_S_BAD_MSG:
>> +             rc = -EINVAL;
>> +             break;
>> +     case VIRTIO_SND_S_NOT_SUPP:
>> +             rc = -EOPNOTSUPP;
>> +             break;
>> +     case VIRTIO_SND_S_IO_ERR:
>> +             rc = -EIO;
>> +             break;
>> +     default:
>> +             rc = -EPERM;
>> +             break;
>> +     }
>> +
>> +on_failure:
>> +     virtsnd_ctl_msg_unref(vdev, msg);
>> +
>> +     return rc;
>> +}
>> +
>> +/**
>> + * virtsnd_ctl_msg_complete() - Complete a control message.
>> + * @snd: VirtIO sound device.
>> + * @msg: Control message.
>> + *
>> + * Context: Any context.
>> + */
>> +void virtsnd_ctl_msg_complete(struct virtio_snd *snd,
>> +                           struct virtio_snd_msg *msg)
>> +{
>> +     list_del(&msg->list);
>> +     complete(&msg->notify);
>> +
>> +     virtsnd_ctl_msg_unref(snd->vdev, msg);
>> +}
>> +
>> +/**
>> + * virtsnd_ctl_query_info() - Query the item configuration from the device.
>> + * @snd: VirtIO sound device.
>> + * @command: Control request code (VIRTIO_SND_R_XXX_INFO).
>> + * @start_id: Item start identifier.
>> + * @count: Item count to query.
>> + * @size: Item information size in bytes.
>> + * @info: Buffer for storing item information.
>> + *
>> + * Context: Any context that permits to sleep.
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +int virtsnd_ctl_query_info(struct virtio_snd *snd, int command, int start_id,
>> +                        int count, size_t size, void *info)
>> +{
>> +     struct virtio_device *vdev = snd->vdev;
>> +     struct virtio_snd_msg *msg;
>> +     struct virtio_snd_query_info *query;
>> +     struct scatterlist sg;
>> +
>> +     sg_init_one(&sg, info, count * size);
>> +
>> +     msg = virtsnd_ctl_msg_alloc_ext(vdev, sizeof(*query),
>> +                                     sizeof(struct virtio_snd_hdr), &sg, 0,
>> +                                     1, GFP_KERNEL);
>> +     if (IS_ERR(msg))
>> +             return PTR_ERR(msg);
>> +
>> +     query = sg_virt(&msg->sg_request);
>> +     query->hdr.code = cpu_to_virtio32(vdev, command);
>> +     query->start_id = cpu_to_virtio32(vdev, start_id);
>> +     query->count = cpu_to_virtio32(vdev, count);
>> +     query->size = cpu_to_virtio32(vdev, size);
>> +
>> +     return virtsnd_ctl_msg_send_sync(snd, msg);
>> +}
>> +
>> +/**
>> + * virtsnd_ctl_notify_cb() - Process all completed control messages.
>> + * @vqueue: Underlying control virtqueue.
>> + *
>> + * This callback function is called upon a vring interrupt request from the
>> + * device.
>> + *
>> + * Context: Interrupt context. Takes and releases the control queue spinlock.
>> + */
>> +void virtsnd_ctl_notify_cb(struct virtqueue *vqueue)
>> +{
>> +     struct virtio_snd *snd = vqueue->vdev->priv;
>> +     struct virtio_snd_queue *queue = virtsnd_control_queue(snd);
>> +     unsigned long flags;
>> +
>> +     spin_lock_irqsave(&queue->lock, flags);
>> +     while (queue->vqueue) {
>> +             virtqueue_disable_cb(queue->vqueue);
>> +
>> +             for (;;) {
>> +                     struct virtio_snd_msg *msg;
>> +                     u32 length;
>> +
>> +                     msg = virtqueue_get_buf(queue->vqueue, &length);
>> +                     if (!msg)
>> +                             break;
>> +
>> +                     virtsnd_ctl_msg_complete(snd, msg);
>> +             }
>> +
>> +             if (unlikely(virtqueue_is_broken(queue->vqueue)))
>> +                     break;
>> +
>> +             if (virtqueue_enable_cb(queue->vqueue))
>> +                     break;
>> +     }
>> +     spin_unlock_irqrestore(&queue->lock, flags);
>> +}
>> diff --git a/sound/virtio/virtio_ctl_msg.h b/sound/virtio/virtio_ctl_msg.h
>> new file mode 100644
>> index 000000000000..0f8de8f2fd2d
>> --- /dev/null
>> +++ b/sound/virtio/virtio_ctl_msg.h
>> @@ -0,0 +1,122 @@
>> +/* 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/>.
>> + */
>> +#ifndef VIRTIO_SND_MSG_H
>> +#define VIRTIO_SND_MSG_H
>> +
>> +#include <linux/atomic.h>
>> +#include <linux/virtio.h>
>> +
>> +struct virtio_snd;
>> +
>> +/**
>> + * struct virtio_snd_msg - Control message.
>> + * @sg_request: Scattergather element containing a device request (header).
>> + * @sg_response: Scattergather element containing a device response (status).
>> + * @list: Pending message list entry.
>> + * @notify: Request completed notification.
>> + * @ref_count: Reference count used to manage a message lifetime.
>> + * @out_sgs: Number of read-only sg elements in the sgs array.
>> + * @in_sgs: Number of write-only sg elements in the sgs array.
>> + * @sgs: Array of sg elements to add to the control virtqueue.
>> + */
>> +struct virtio_snd_msg {
>> +/* public: */
>> +     struct scatterlist sg_request;
>> +     struct scatterlist sg_response;
>> +/* private: internal use only */
>> +     struct list_head list;
>> +     struct completion notify;
>> +     atomic_t ref_count;
>> +     unsigned int out_sgs;
>> +     unsigned int in_sgs;
>> +     struct scatterlist *sgs[0];
>> +};
>> +
>> +/**
>> + * virtsnd_ctl_msg_ref() - Increment reference counter for the message.
>> + * @vdev: VirtIO parent device.
>> + * @msg: Control message.
>> + *
>> + * Context: Any context.
>> + */
>> +static inline void virtsnd_ctl_msg_ref(struct virtio_device *vdev,
>> +                                    struct virtio_snd_msg *msg)
>> +{
>> +     atomic_inc(&msg->ref_count);
>> +}
>> +
>> +/**
>> + * virtsnd_ctl_msg_unref() - Decrement reference counter for the message.
>> + * @vdev: VirtIO parent device.
>> + * @msg: Control message.
>> + *
>> + * The message will be freed when the ref_count value is 0.
>> + *
>> + * Context: Any context.
>> + */
>> +static inline void virtsnd_ctl_msg_unref(struct virtio_device *vdev,
>> +                                      struct virtio_snd_msg *msg)
>> +{
>> +     if (!atomic_dec_return(&msg->ref_count))
>> +             devm_kfree(&vdev->dev, msg);
>> +}
>> +
>> +struct virtio_snd_msg *virtsnd_ctl_msg_alloc_ext(struct virtio_device *vdev,
>> +                                              size_t request_size,
>> +                                              size_t response_size,
>> +                                              struct scatterlist *sgs,
>> +                                              unsigned int out_sgs,
>> +                                              unsigned int in_sgs,
>> +                                              gfp_t gfp);
>> +
>> +/**
>> + * virtsnd_ctl_msg_alloc() - Simplified control message allocation.
>> + * @vdev: VirtIO parent device.
>> + * @request_size: Size of request header (pointed to by sg_request field).
>> + * @response_size: Size of response header (pointed to by sg_response field).
>> + * @gfp: Kernel flags for memory allocation.
>> + *
>> + * The message will be automatically freed when the ref_count value is 0.
>> + *
>> + * Context: Any context. May sleep if @gfp flags permit.
>> + * Return: Allocated message on success, ERR_PTR(-errno) on failure.
>> + */
>> +static inline
>> +struct virtio_snd_msg *virtsnd_ctl_msg_alloc(struct virtio_device *vdev,
>> +                                          size_t request_size,
>> +                                          size_t response_size, gfp_t gfp)
>> +{
>> +     return virtsnd_ctl_msg_alloc_ext(vdev, request_size, response_size,
>> +                                      NULL, 0, 0, gfp);
>> +}
>> +
>> +int virtsnd_ctl_msg_send(struct virtio_snd *snd, struct virtio_snd_msg *msg);
>> +
>> +int virtsnd_ctl_msg_send_sync(struct virtio_snd *snd,
>> +                           struct virtio_snd_msg *msg);
>> +
>> +void virtsnd_ctl_msg_complete(struct virtio_snd *snd,
>> +                           struct virtio_snd_msg *msg);
>> +
>> +int virtsnd_ctl_query_info(struct virtio_snd *snd, int command, int start_id,
>> +                        int count, size_t size, void *info);
>> +
>> +void virtsnd_ctl_notify_cb(struct virtqueue *vqueue);
>> +
>> +#endif /* VIRTIO_SND_MSG_H */
>> 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;
>> +}
>> +
>> +/**
>> + * 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);
>> +     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: {
>> +                     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) {
>> +                             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;
>> +     }
>> +     }
>> +}
>> diff --git a/sound/virtio/virtio_pcm.h b/sound/virtio/virtio_pcm.h
>> new file mode 100644
>> index 000000000000..73fb4d9dc524
>> --- /dev/null
>> +++ b/sound/virtio/virtio_pcm.h
>> @@ -0,0 +1,89 @@
>> +/* 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/>.
>> + */
>> +#ifndef VIRTIO_SND_PCM_H
>> +#define VIRTIO_SND_PCM_H
>> +
>> +#include <linux/atomic.h>
>> +#include <linux/virtio_config.h>
>> +#include <sound/pcm.h>
>> +
>> +struct virtio_pcm;
>> +
>> +/**
>> + * struct virtio_pcm_substream - VirtIO PCM substream.
>> + * @snd: VirtIO sound device.
>> + * @nid: Function group node identifier.
>> + * @sid: Stream identifier.
>> + * @direction: Stream data flow direction (SNDRV_PCM_STREAM_XXX).
>> + * @features: Stream VirtIO feature bit map (1 << VIRTIO_SND_PCM_F_XXX).
>> + * @substream: Kernel ALSA substream.
>> + * @hw: Kernel ALSA substream hardware descriptor.
>> + */
>> +struct virtio_pcm_substream {
>> +     struct virtio_snd *snd;
>> +     unsigned int nid;
>> +     unsigned int sid;
>> +     u32 direction;
>> +     u32 features;
>> +     struct snd_pcm_substream *substream;
>> +     struct snd_pcm_hardware hw;
>> +};
>> +
>> +/**
>> + * struct virtio_pcm_stream - VirtIO PCM stream.
>> + * @substreams: Virtio substreams belonging to the stream.
>> + * @nsubstreams: Number of substreams.
>> + */
>> +struct virtio_pcm_stream {
>> +     struct virtio_pcm_substream **substreams;
>> +     unsigned int nsubstreams;
>> +};
>> +
>> +/**
>> + * struct virtio_pcm - VirtIO PCM device.
>> + * @list: PCM list entry.
>> + * @nid: Function group node identifier.
>> + * @pcm: Kernel PCM device.
>> + * @streams: VirtIO PCM streams (playback and capture).
>> + */
>> +struct virtio_pcm {
>> +     struct list_head list;
>> +     unsigned int nid;
>> +     struct snd_pcm *pcm;
>> +     struct virtio_pcm_stream streams[SNDRV_PCM_STREAM_LAST + 1];
>> +};
>> +
>> +int virtsnd_pcm_validate(struct virtio_device *vdev);
>> +
>> +int virtsnd_pcm_parse_cfg(struct virtio_snd *snd);
>> +
>> +int virtsnd_pcm_build_devs(struct virtio_snd *snd);
>> +
>> +void virtsnd_pcm_event(struct virtio_snd *snd, struct virtio_snd_event *event);
>> +
>> +void virtsnd_pcm_tx_notify_cb(struct virtqueue *vqueue);
>> +
>> +void virtsnd_pcm_rx_notify_cb(struct virtqueue *vqueue);
>> +
>> +struct virtio_pcm *virtsnd_pcm_find(struct virtio_snd *snd, unsigned int nid);
>> +
>> +struct virtio_pcm *virtsnd_pcm_find_or_create(struct virtio_snd *snd,
>> +                                           unsigned int nid);
>> +
>> +#endif /* VIRTIO_SND_PCM_H */
>> --
>> 2.30.0
>>
>>
> 
> 

-- 
Anton Yakovlev
Senior Software Engineer

OpenSynergy GmbH
Rotherstr. 20, 10245 Berlin

Phone: +49 30 60 98 54 0
E-Mail: anton.yakovlev@opensynergy.com

www.opensynergy.com

Handelsregister/Commercial Registry: Amtsgericht Charlottenburg, HRB 108616B
Geschäftsführer/Managing Director: Regis Adjamah