[v3,1/3] Add virtio-sound device

This patch adds an audio device implementing the recent virtio sound
spec (1.2).

PCM functionality is implemented, and jack[0], chmaps[1] messages are
at the moment left unimplemented.

PS2: This patch was based on a draft patch posted by OpenSynergy in 2019. [2]

[0]: https://www.kernel.org/doc/html/latest/sound/designs/jack-controls.html
[1]: https://www.kernel.org/doc/html/latest/sound/designs/channel-mapping-api.html
[2]: https://github.com/OpenSynergy/qemu/commit/5a2f350eec5d157b90d9c7b40a8e603f4da92471#diff-fa5c10be8476fb5385a280885d527b0b40dfc11ddcc74369fce085d8b5b17bbd

Signed-off-by: Emmanouil Pitsidianakis <manos.pitsidianakis@linaro.org>
Signed-off-by: Igor Skalkin <Igor.Skalkin@opensynergy.com>
Signed-off-by: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
base-commit: 361d539735
---
 MAINTAINERS                    |    6 +
 hw/virtio/Kconfig              |    5 +
 hw/virtio/meson.build          |    1 +
 hw/virtio/trace-events         |   21 +
 hw/virtio/virtio-snd.c         | 1121 ++++++++++++++++++++++++++++++++
 include/hw/virtio/virtio-snd.h |  194 ++++++
 6 files changed, 1348 insertions(+)
 create mode 100644 hw/virtio/virtio-snd.c
 create mode 100644 include/hw/virtio/virtio-snd.h

Hi Manos,

I only have style comments.

On 18/7/23 20:04, Manos Pitsidianakis wrote:
> 
> This patch adds an audio device implementing the recent virtio sound
> spec (1.2).
> 
> PCM functionality is implemented, and jack[0], chmaps[1] messages are
> at the moment left unimplemented.
> 
> PS2: This patch was based on a draft patch posted by OpenSynergy in 2019. [2]
> 
> [0]: https://www.kernel.org/doc/html/latest/sound/designs/jack-controls.html
> [1]: https://www.kernel.org/doc/html/latest/sound/designs/channel-mapping-api.html
> [2]: https://github.com/OpenSynergy/qemu/commit/5a2f350eec5d157b90d9c7b40a8e603f4da92471#diff-fa5c10be8476fb5385a280885d527b0b40dfc11ddcc74369fce085d8b5b17bbd
> 
> Signed-off-by: Emmanouil Pitsidianakis <manos.pitsidianakis@linaro.org>
> Signed-off-by: Igor Skalkin <Igor.Skalkin@opensynergy.com>
> Signed-off-by: Anton Yakovlev <Anton.Yakovlev@opensynergy.com>

---

> base-commit: 361d539735
> ---
>   MAINTAINERS                    |    6 +
>   hw/virtio/Kconfig              |    5 +
>   hw/virtio/meson.build          |    1 +
>   hw/virtio/trace-events         |   21 +
>   hw/virtio/virtio-snd.c         | 1121 ++++++++++++++++++++++++++++++++
>   include/hw/virtio/virtio-snd.h |  194 ++++++
>   6 files changed, 1348 insertions(+)
>   create mode 100644 hw/virtio/virtio-snd.c
>   create mode 100644 include/hw/virtio/virtio-snd.h


> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 7109cf1a3b..8f3953dc28 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -154,3 +154,24 @@ virtio_pmem_flush_done(int type) "fsync return=%d"
>   virtio_gpio_start(void) "start"
>   virtio_gpio_stop(void) "stop"
>   virtio_gpio_set_status(uint8_t status) "0x%x"
> +
> +#virtio-snd.c
> +virtio_snd_pcm_stream_flush(int stream) "flushing stream %d"

stream is unsigned.

> +virtio_snd_handle_ctrl(void *vdev, void *vq) "snd %p: handle ctrl event for queue %p"

> +#virtio_snd_handle_jack_info(int jack) "VIRTIO_SND_JACK_INFO called for jack %d"
> +#virtio_snd_handle_jack_remap(void) "VIRTIO_SND_PCM_JACK_REMAP called"

No need to add commented thus unused lines.

> +virtio_snd_handle_pcm_info(int stream) "VIRTIO_SND_R_PCM_INFO called for stream %d"
> +virtio_snd_handle_pcm_set_params(int stream) "VIRTIO_SND_PCM_SET_PARAMS called for stream %d"
> +virtio_snd_handle_pcm_start_stop(const char *code, int stream) "%s called for stream %d"
> +virtio_snd_handle_pcm_release(int stream) "VIRTIO_SND_PCM_RELEASE called for stream %d"
> +virtio_snd_handle_chmap_info(void) "VIRTIO_SND_CHMAP_INFO called"
> +virtio_snd_handle_xfer(void) "tx/rx queue callback called"
> +virtio_snd_handle_event(void) "event queue callback called"
> +virtio_snd_realize(void *snd) "snd %p: realize"
> +virtio_snd_unrealize(void *snd) "snd %p: unrealize"
> +virtio_snd_get_features(void *vdev, uint64_t features) "snd %p: get_features 0x%"PRIx64
> +virtio_snd_get_config(void *vdev, uint32_t jacks, uint32_t streams, uint32_t chmaps) "snd %p: get_config jacks=%d streams=%d chmaps=%d"

"%u" for unsigned.

> +virtio_snd_set_config(void *vdev, uint32_t jacks, uint32_t new_jacks, uint32_t streams, uint32_t new_streams, uint32_t chmaps, uint32_t new_chmaps) "snd %p: set_config jacks from %d->%d, streams from %d->%d, chmaps from %d->%d"
> +virtio_snd_vm_state_running(void) "vm state running"
> +virtio_snd_vm_state_stopped(void) "vm state stopped"
> +virtio_snd_handle_code(int val, const char *code) "ctrl code msg val = %d == %s"

val (virtio_snd_hdr.code) is unsigned.

> diff --git a/hw/virtio/virtio-snd.c b/hw/virtio/virtio-snd.c
> new file mode 100644
> index 0000000000..dbf8d8162f
> --- /dev/null
> +++ b/hw/virtio/virtio-snd.c
> @@ -0,0 +1,1121 @@
> +/*
> + * VIRTIO Sound Device conforming to
> + *
> + * "Virtual I/O Device (VIRTIO) Version 1.2
> + * Committee Specification Draft 01
> + * 09 May 2022"
> + *
> + * <https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-52900014>
> + *
> + * Copyright (c) 2023 Emmanouil Pitsidianakis <manos.pitsidianakis@linaro.org>
> + * Copyright (C) 2019 OpenSynergy GmbH
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * (at your option) any later version.  See the COPYING file in the
> + * top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/iov.h"
> +#include "qemu/log.h"
> +#include "include/qemu/lockable.h"
> +#include "sysemu/runstate.h"
> +#include "trace.h"
> +#include "qapi/error.h"
> +#include "hw/virtio/virtio-snd.h"
> +
> +#define VIRTIO_SOUND_VM_VERSION 1
> +
> +#define VIRTIO_SOUND_JACK_DEFAULT 0
> +#define VIRTIO_SOUND_STREAM_DEFAULT 1
> +#define VIRTIO_SOUND_CHMAP_DEFAULT 0
> +
> +#define VIRTIO_SOUND_HDA_FN_NID 0
> +
> +static uint32_t supported_formats = 1 << VIRTIO_SND_PCM_FMT_S8
> +                      | 1 << VIRTIO_SND_PCM_FMT_U8

Misaligned.

Consider:

   = BIT(VIRTIO_SND_PCM_FMT_S8)
   | BIT(VIRTIO_SND_PCM_FMT_S8)
   | ...

> +                      | 1 << VIRTIO_SND_PCM_FMT_S16
> +                      | 1 << VIRTIO_SND_PCM_FMT_U16
> +                      | 1 << VIRTIO_SND_PCM_FMT_S32
> +                      | 1 << VIRTIO_SND_PCM_FMT_U32
> +                      | 1 << VIRTIO_SND_PCM_FMT_FLOAT;
> +
> +static uint32_t supported_rates = 1 << VIRTIO_SND_PCM_RATE_5512
> +                    | 1 << VIRTIO_SND_PCM_RATE_8000
> +                    | 1 << VIRTIO_SND_PCM_RATE_11025
> +                    | 1 << VIRTIO_SND_PCM_RATE_16000
> +                    | 1 << VIRTIO_SND_PCM_RATE_22050
> +                    | 1 << VIRTIO_SND_PCM_RATE_32000
> +                    | 1 << VIRTIO_SND_PCM_RATE_44100
> +                    | 1 << VIRTIO_SND_PCM_RATE_48000
> +                    | 1 << VIRTIO_SND_PCM_RATE_64000
> +                    | 1 << VIRTIO_SND_PCM_RATE_88200
> +                    | 1 << VIRTIO_SND_PCM_RATE_96000
> +                    | 1 << VIRTIO_SND_PCM_RATE_176400
> +                    | 1 << VIRTIO_SND_PCM_RATE_192000
> +                    | 1 << VIRTIO_SND_PCM_RATE_384000;
> +
> +static const VMStateDescription vmstate_virtio_snd_device = {
> +    .name = TYPE_VIRTIO_SND,
> +    .version_id = VIRTIO_SOUND_VM_VERSION,
> +    .minimum_version_id = VIRTIO_SOUND_VM_VERSION,
> +};
> +
> +static const VMStateDescription vmstate_virtio_snd = {
> +    .name = "virtio-sound",
> +    .minimum_version_id = VIRTIO_SOUND_VM_VERSION,
> +    .version_id = VIRTIO_SOUND_VM_VERSION,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_VIRTIO_DEVICE,
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
> +static Property virtio_snd_properties[] = {
> +    DEFINE_AUDIO_PROPERTIES(VirtIOSound, card),
> +    DEFINE_PROP_UINT32("jacks", VirtIOSound, snd_conf.jacks,
> +                       VIRTIO_SOUND_JACK_DEFAULT),
> +    DEFINE_PROP_UINT32("streams", VirtIOSound, snd_conf.streams,
> +                       VIRTIO_SOUND_STREAM_DEFAULT),
> +    DEFINE_PROP_UINT32("chmaps", VirtIOSound, snd_conf.chmaps,
> +                       VIRTIO_SOUND_CHMAP_DEFAULT),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void
> +virtio_snd_get_config(VirtIODevice *vdev, uint8_t *config)
> +{
> +    VirtIOSound *s = VIRTIO_SND(vdev);
> +    trace_virtio_snd_get_config(vdev,
> +                                s->snd_conf.jacks,
> +                                s->snd_conf.streams,
> +                                s->snd_conf.chmaps);
> +
> +    memcpy(config, &s->snd_conf, sizeof(s->snd_conf));
> +}
> +
> +static void
> +virtio_snd_set_config(VirtIODevice *vdev, const uint8_t *config)
> +{
> +    VirtIOSound *s = VIRTIO_SND(vdev);
> +    const virtio_snd_config *sndconfig =
> +        (const virtio_snd_config *)config;
> +
> +
> +   trace_virtio_snd_set_config(vdev,
> +                               s->snd_conf.jacks,
> +                               sndconfig->jacks,
> +                               s->snd_conf.streams,
> +                               sndconfig->streams,
> +                               s->snd_conf.chmaps,
> +                               sndconfig->chmaps);
> +
> +    memcpy(&s->snd_conf, sndconfig, sizeof(s->snd_conf));
> +}
> +
> +static void virtio_snd_process_cmdq(VirtIOSound *s);
> +static void virtio_snd_pcm_flush(VirtIOSoundPCMStream *stream);
> +static void virtio_snd_pcm_out_cb(void *data, int available);
> +static uint32_t virtio_snd_pcm_read_write(VirtIOSoundPCMStream *stream,
> +                                          VirtQueue *vq,
> +                                          VirtQueueElement *element,
> +                                          bool read);
> +
> +/*
> + * Get a specific stream from the virtio sound card device.
> + * Returns NULL if @stream_id is invalid or not allocated.
> + *
> + * @s: VirtIOSound device
> + * @stream_id: stream id
> + */
> +static VirtIOSoundPCMStream *virtio_snd_pcm_get_stream(VirtIOSound *s,
> +                                                       uint32_t stream_id)
> +{
> +    return stream_id >= s->snd_conf.streams ? NULL : s->pcm->streams[stream_id];
> +}
> +
> +/*
> + * Get params for a specific stream.
> + *
> + * @s: VirtIOSound device
> + * @stream_id: stream id
> + */
> +static VirtIOSoundPCMParams *virtio_snd_pcm_get_params(VirtIOSound *s,
> +                                                       uint32_t stream_id)
> +{
> +    return stream_id >= s->snd_conf.streams ? NULL
> +        : s->pcm->pcm_params[stream_id];
> +}
> +
> +/*
> + * Handle the VIRTIO_SND_R_PCM_INFO request.
> + * The function writes the info structs to the request element.
> + *
> + * @s: VirtIOSound device
> + * @cmd: The request command queue element from VirtIOSound cmdq field
> + */
> +static void virtio_snd_handle_pcm_info(VirtIOSound *s,
> +                                       virtio_snd_ctrl_command *cmd)
> +{
> +    virtio_snd_query_info req;
> +    uint32_t sz;
> +    VirtIOSoundPCMStream *stream = NULL;
> +    g_autofree virtio_snd_pcm_info *pcm_info = NULL;
> +
> +    sz = iov_to_buf(cmd->elem->out_sg,
> +                    cmd->elem->out_num,
> +                    0,
> +                    &req,
> +                    sizeof(req));
> +    if (sz != sizeof(virtio_snd_query_info)) {
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +        return;
> +    }
> +
> +    if (iov_size(cmd->elem->in_sg, cmd->elem->in_num) <
> +        sizeof(virtio_snd_hdr) + req.size * req.count) {
> +        error_report("pcm info: buffer too small, got: %lu, needed: %lu",
> +                iov_size(cmd->elem->in_sg, cmd->elem->in_num),
> +                sizeof(virtio_snd_pcm_info));
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +        return;
> +    }
> +
> +    pcm_info = g_new0(virtio_snd_pcm_info, req.count);
> +    for (int i = req.start_id; i < req.start_id + req.count; i++) {
> +        trace_virtio_snd_handle_pcm_info(i);
> +        stream = virtio_snd_pcm_get_stream(s, i);
> +
> +        if (!stream) {
> +            error_report("Invalid stream id: %d", i);
> +            cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +            return;
> +        }
> +
> +        pcm_info[i - req.start_id].hdr.hda_fn_nid = stream->info.hdr.hda_fn_nid;
> +        pcm_info[i - req.start_id].features = stream->features;
> +        pcm_info[i - req.start_id].formats = stream->formats;
> +        pcm_info[i - req.start_id].rates = stream->rates;
> +        pcm_info[i - req.start_id].direction = stream->direction;
> +        pcm_info[i - req.start_id].channels_min = stream->channels_min;
> +        pcm_info[i - req.start_id].channels_max = stream->channels_max;
> +
> +        memset(&pcm_info[i].padding, 0, sizeof(pcm_info[i].padding));
> +    }
> +
> +    cmd->resp.code = VIRTIO_SND_S_OK;
> +
> +    iov_from_buf(cmd->elem->in_sg,
> +                 cmd->elem->in_num,
> +                 sizeof(virtio_snd_hdr),
> +                 pcm_info,
> +                 sizeof(virtio_snd_pcm_info) * req.count);
> +
> +    return;
> +}
> +
> +/*
> + * Set the given stream params.
> + * Called by both virtio_snd_handle_pcm_set_params and during device
> + * initialization.
> + * Returns the response status code. (VIRTIO_SND_S_*).
> + *
> + * @s: VirtIOSound device
> + * @params: The PCM params as defined in the virtio specification
> + */
> +static
> +uint32_t virtio_snd_pcm_set_params_impl(VirtIOSound *s,
> +                                        virtio_snd_pcm_set_params *params)
> +{
> +    VirtIOSoundPCMParams *st_params;
> +    uint32_t stream_id = params->hdr.stream_id;
> +
> +    if (stream_id > s->snd_conf.streams || !(s->pcm->pcm_params)) {
> +        virtio_error(VIRTIO_DEVICE(s), "Streams have not been initialized.\n");
> +        return VIRTIO_SND_S_BAD_MSG;
> +    }
> +
> +    if (!s->pcm->pcm_params[stream_id]) {
> +        s->pcm->pcm_params[stream_id] = g_new0(VirtIOSoundPCMParams, 1);
> +    }
> +    st_params = virtio_snd_pcm_get_params(s, stream_id);
> +
> +    st_params->features = params->features;
> +    st_params->buffer_bytes = params->buffer_bytes;
> +    st_params->period_bytes = params->period_bytes;
> +
> +    if (params->channels < 1 || params->channels > AUDIO_MAX_CHANNELS) {
> +        error_report("Number of channels is not supported.");
> +        return VIRTIO_SND_S_NOT_SUPP;
> +    }
> +    st_params->channels = params->channels;
> +
> +    if (!(supported_formats & (1 << params->format))) {

Consider BIT(params->format).

> +        error_report("Stream format is not supported.");
> +        return VIRTIO_SND_S_NOT_SUPP;
> +    }
> +    st_params->format = params->format;
> +
> +    if (!(supported_rates & (1 << params->rate))) {
> +        error_report("Stream rate is not supported.");
> +        return VIRTIO_SND_S_NOT_SUPP;
> +    }
> +    st_params->rate = params->rate;
> +    st_params->period_bytes = params->period_bytes;
> +    st_params->buffer_bytes = params->buffer_bytes;
> +
> +    return VIRTIO_SND_S_OK;
> +}
> +
> +/*
> + * Handles the VIRTIO_SND_R_PCM_SET_PARAMS request.
> + *
> + * @s: VirtIOSound device
> + * @cmd: The request command queue element from VirtIOSound cmdq field
> + */
> +static void virtio_snd_handle_pcm_set_params(VirtIOSound *s,
> +                                             virtio_snd_ctrl_command *cmd)
> +{
> +    virtio_snd_pcm_set_params req;
> +    uint32_t sz;
> +
> +    sz = iov_to_buf(cmd->elem->out_sg,
> +                    cmd->elem->out_num,
> +                    0,
> +                    &req,
> +                    sizeof(req));
> +    if (sz != sizeof(virtio_snd_pcm_set_params)) {
> +        cmd->resp.code = VIRTIO_SND_S_NOT_SUPP;
> +        return;
> +    }
> +
> +    trace_virtio_snd_handle_pcm_set_params(req.hdr.stream_id);
> +    cmd->resp.code = virtio_snd_pcm_set_params_impl(s, &req);
> +
> +    return;
> +}
> +
> +/*
> + * Get a QEMU Audiosystem compatible format value from a VIRTIO_SND_PCM_FMT_*
> + */
> +static AudioFormat virtio_snd_get_qemu_format(uint32_t format)
> +{
> +    #define CASE(FMT)               \
> +    case VIRTIO_SND_PCM_FMT_##FMT:  \
> +        return AUDIO_FORMAT_##FMT;
> +
> +    switch (format) {
> +    CASE(U8)
> +    CASE(S8)
> +    CASE(U16)
> +    CASE(S16)
> +    CASE(U32)
> +    CASE(S32)
> +    case VIRTIO_SND_PCM_FMT_FLOAT:
> +        return AUDIO_FORMAT_F32;
> +    default:

   g_assert_not_reached();

> +        return -1;
> +    }
> +
> +    #undef CASE
> +}
> +
> +/*
> + * Get a QEMU Audiosystem compatible frequency value from a
> + * VIRTIO_SND_PCM_RATE_*
> + */
> +static uint32_t virtio_snd_get_qemu_freq(uint32_t rate)
> +{
> +    #define CASE(RATE)               \
> +    case VIRTIO_SND_PCM_RATE_##RATE: \
> +        return RATE;
> +
> +    switch (rate) {
> +    CASE(5512)
> +    CASE(8000)
> +    CASE(11025)
> +    CASE(16000)
> +    CASE(22050)
> +    CASE(32000)
> +    CASE(44100)
> +    CASE(48000)
> +    CASE(64000)
> +    CASE(88200)
> +    CASE(96000)
> +    CASE(176400)
> +    CASE(192000)
> +    CASE(384000)
> +    default:

   g_assert_not_reached();

> +        return -1;
> +    }
> +
> +    #undef CASE
> +}
> +
> +/*
> + * Get QEMU Audiosystem compatible audsettings from virtio based pcm stream
> + * params.
> + */
> +static void virtio_snd_get_qemu_audsettings(audsettings *as,
> +                                            VirtIOSoundPCMParams *params)
> +{
> +    as->nchannels = MIN(AUDIO_MAX_CHANNELS, params->channels);
> +    as->fmt = virtio_snd_get_qemu_format(params->format);
> +    as->freq = virtio_snd_get_qemu_freq(params->rate);
> +    as->endianness = AUDIO_HOST_ENDIANNESS;
> +}
> +
> +/*
> + * Prepares a VirtIOSound card stream.
> + * Returns the response status code. (VIRTIO_SND_S_*).
> + *
> + * @s: VirtIOSound device
> + * @stream_id: stream id
> + */
> +static uint32_t virtio_snd_pcm_prepare_impl(VirtIOSound *s, uint32_t stream_id)
> +{
> +    audsettings as;
> +    VirtIOSoundPCMParams *params;
> +    VirtIOSoundPCMStream *stream;
> +
> +    if (!s->pcm->streams
> +            || !s->pcm->pcm_params
> +            || !s->pcm->pcm_params[stream_id]) {
> +        return VIRTIO_SND_S_BAD_MSG;
> +    }
> +
> +    params = virtio_snd_pcm_get_params(s, stream_id);
> +    if (!params) {
> +        return VIRTIO_SND_S_BAD_MSG;
> +    }
> +
> +    virtio_snd_get_qemu_audsettings(&as, params);
> +
> +    stream = g_new0(VirtIOSoundPCMStream, 1);
> +
> +    stream->id = stream_id;
> +    stream->pcm = s->pcm;
> +    stream->direction = stream_id < s->snd_conf.streams / 2 +
> +        (s->snd_conf.streams & 1) ? VIRTIO_SND_D_OUTPUT : VIRTIO_SND_D_INPUT;
> +    stream->info.hdr.hda_fn_nid = VIRTIO_SOUND_HDA_FN_NID;
> +    stream->features = 0;
> +    stream->channels_min = 1;
> +    stream->channels_max = as.nchannels;
> +    stream->formats = supported_formats;
> +    stream->rates = supported_rates;
> +    stream->s = s;
> +
> +    stream->buffer_bytes = params->buffer_bytes;
> +    stream->period_bytes = params->period_bytes;
> +
> +    stream->positions[0] = VIRTIO_SND_CHMAP_FL;
> +    stream->positions[1] = VIRTIO_SND_CHMAP_FR;
> +
> +
> +    if (stream->direction == VIRTIO_SND_D_OUTPUT) {
> +        stream->voice.out = AUD_open_out(&s->card,
> +                                         stream->voice.out,
> +                                         "virtio_snd_card",
> +                                         stream,
> +                                         virtio_snd_pcm_out_cb,
> +                                         &as);
> +
> +    } else {
> +        qemu_log_mask(LOG_UNIMP, "virtio_snd: input/capture is unimplemented.");
> +        /*
> +         * stream->voice.in = AUD_open_in(&s->card,
> +         *                                stream->voice.in,
> +         *                                "virtio_snd_card",
> +         *                                stream,
> +         *                                virtio_snd_input_cb,
> +         *                                &as);
> +         */
> +    }
> +
> +    stream->as = as;
> +    stream->desired_as = stream->as;
> +    qemu_mutex_init(&stream->queue_mutex);
> +    QSIMPLEQ_INIT(&stream->queue);
> +
> +    s->pcm->streams[stream_id] = stream;
> +
> +    return VIRTIO_SND_S_OK;
> +}
> +
> +/*
> + * Handles VIRTIO_SND_R_PCM_PREPARE.
> + *
> + * @s: VirtIOSound device
> + * @cmd: The request command queue element from VirtIOSound cmdq field
> + */
> +static void virtio_snd_handle_pcm_prepare(VirtIOSound *s,
> +                                          virtio_snd_ctrl_command *cmd)
> +{
> +    uint32_t stream_id;
> +    size_t sz;
> +
> +    sz = iov_to_buf(cmd->elem->out_sg,
> +                    cmd->elem->out_num,
> +                    sizeof(virtio_snd_hdr),
> +                    &stream_id,
> +                    sizeof(stream_id));

        cmd->resp.code = sz == sizeof(uint32_t)
                       ? virtio_snd_pcm_prepare_impl(s, stream_id)
                       : VIRTIO_SND_S_BAD_MSG;
    }

> +    if (sz != sizeof(uint32_t)) {
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +        return;
> +    }
> +
> +    cmd->resp.code = virtio_snd_pcm_prepare_impl(s, stream_id);
> +    return;
> +}
> +
> +/*
> + * Handles VIRTIO_SND_R_PCM_START.
> + *
> + * @s: VirtIOSound device
> + * @cmd: The request command queue element from VirtIOSound cmdq field
> + * @start: whether to start or stop the device
> + */
> +static void virtio_snd_handle_pcm_start_stop(VirtIOSound *s,
> +                                             virtio_snd_ctrl_command *cmd,
> +                                             bool start)
> +{
> +    VirtIOSoundPCMStream *stream;
> +    virtio_snd_pcm_hdr req;
> +    size_t sz;
> +
> +    sz = iov_to_buf(cmd->elem->out_sg,
> +                    cmd->elem->out_num,
> +                    0,
> +                    &req,
> +                    sizeof(req));
> +    if (sz != sizeof(virtio_snd_pcm_hdr)) {
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +        return;
> +    }
> +
> +    cmd->resp.code = VIRTIO_SND_S_OK;
> +    trace_virtio_snd_handle_pcm_start_stop(start ? "VIRTIO_SND_R_PCM_START" :
> +            "VIRTIO_SND_R_PCM_STOP", req.stream_id);
> +
> +    stream = virtio_snd_pcm_get_stream(s, req.stream_id);
> +
> +    if (stream) {
> +        if (stream->direction == VIRTIO_SND_D_OUTPUT) {
> +            AUD_set_active_out(stream->voice.out, start);
> +        }
> +    } else {
> +        error_report("Invalid stream id: %d", req.stream_id);
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +    }
> +    return;

No need to return at the end of void functions.

> +}
> +
> +/*
> + * Returns the number of bytes that have not been passed to AUD_write yet.
> + *
> + * @stream: VirtIOSoundPCMStream
> + */
> +static int virtio_snd_pcm_get_pending_bytes(VirtIOSoundPCMStream *stream)

size_t?

> +{
> +    VirtIOSoundPCMBlock *block;
> +    VirtIOSoundPCMBlock *next;
> +    int size = 0;

size_t?

> +    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> +        QSIMPLEQ_FOREACH_SAFE(block, &stream->queue, entry, next) {
> +            size += block->size;
> +        }
> +    }
> +    return size;
> +}
> +
> +/*
> + * Releases the buffer resources allocated to a stream. Seperated from the
> + * handler so that the code can be reused in the unrealize function. Returns
> + * the response status code. (VIRTIO_SND_S_*).
> + *
> + * @stream: VirtIOSoundPCMStream stream
> + * @stream_id: stream id
> + */
> +static uint32_t virtio_snd_pcm_release_impl(VirtIOSoundPCMStream *stream,
> +                                            uint32_t stream_id)
> +{
> +    if (virtio_snd_pcm_get_pending_bytes(stream)) {
> +        /*
> +         * virtio-v1.2-csd01, 5.14.6.6.5.1,
> +         * Device Requirements: Stream Release
> +         *
> +         * - The device MUST complete all pending I/O messages for the
> +         *   specified stream ID.
> +         * - The device MUST NOT complete the control request while there
> +         *   are pending I/O messages for the specified stream ID.
> +         */
> +        virtio_snd_process_cmdq(stream->s);
> +        trace_virtio_snd_pcm_stream_flush(stream_id);
> +        virtio_snd_pcm_flush(stream);
> +    }
> +
> +    return VIRTIO_SND_S_OK;
> +}
> +
> +/*
> + * Handles VIRTIO_SND_R_PCM_RELEASE.
> + *
> + * @s: VirtIOSound device
> + * @cmd: The request command queue element from VirtIOSound cmdq field
> + */
> +static void virtio_snd_handle_pcm_release(VirtIOSound *s,
> +                                          virtio_snd_ctrl_command *cmd)
> +{
> +    uint32_t stream_id;
> +    size_t sz;
> +    VirtIOSoundPCMStream *stream;
> +
> +    sz = iov_to_buf(cmd->elem->out_sg,
> +                    cmd->elem->out_num,
> +                    sizeof(virtio_snd_hdr),
> +                    &stream_id,
> +                    sizeof(stream_id));
> +    if (sz != sizeof(uint32_t)) {
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +        return;
> +    }
> +
> +    trace_virtio_snd_handle_pcm_release(stream_id);
> +
> +    stream = virtio_snd_pcm_get_stream(s, stream_id);
> +    if (!stream) {
> +        error_report("already released stream %d", stream_id);
> +        virtio_error(VIRTIO_DEVICE(s), "already released stream %d", stream_id);
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +        return;
> +    }
> +    cmd->resp.code = virtio_snd_pcm_release_impl(stream, stream_id);
> +    return;
> +}
> +
> +/*
> + * The actual processing done in virtio_snd_process_cmdq().
> + *
> + * @s: VirtIOSound device
> + * @cmd: control command request
> + */
> +static inline void
> +process_cmd(VirtIOSound *s, virtio_snd_ctrl_command *cmd)
> +{
> +    VIRTIO_SND_FILL_CMD(cmd->ctrl);
> +
> +    trace_virtio_snd_handle_code(cmd->ctrl.code,
> +                                 print_code(cmd->ctrl.code));
> +
> +    switch (cmd->ctrl.code) {
> +    case VIRTIO_SND_R_JACK_INFO:
> +    case VIRTIO_SND_R_JACK_REMAP:
> +        qemu_log_mask(LOG_UNIMP,
> +                     "virtio_snd: jack functionality is unimplemented.");
> +        cmd->resp.code = VIRTIO_SND_S_NOT_SUPP;
> +        break;
> +    case VIRTIO_SND_R_PCM_INFO:
> +        virtio_snd_handle_pcm_info(s, cmd);
> +        break;
> +    case VIRTIO_SND_R_PCM_SET_PARAMS:
> +        virtio_snd_handle_pcm_set_params(s, cmd);
> +        break;
> +    case VIRTIO_SND_R_PCM_PREPARE:
> +        virtio_snd_handle_pcm_prepare(s, cmd);
> +        break;
> +    case VIRTIO_SND_R_PCM_START:
> +        virtio_snd_handle_pcm_start_stop(s, cmd, true);
> +        break;
> +    case VIRTIO_SND_R_PCM_STOP:
> +        virtio_snd_handle_pcm_start_stop(s, cmd, false);
> +        break;
> +    case VIRTIO_SND_R_PCM_RELEASE:
> +        virtio_snd_handle_pcm_release(s, cmd);
> +        break;
> +    case VIRTIO_SND_R_CHMAP_INFO:
> +        qemu_log_mask(LOG_UNIMP,
> +                     "virtio_snd: chmap info functionality is unimplemented.");
> +        trace_virtio_snd_handle_chmap_info();
> +        cmd->resp.code = VIRTIO_SND_S_NOT_SUPP;
> +        break;
> +    default:
> +        /* error */
> +        error_report("virtio snd header not recognized: %d", cmd->ctrl.code);
> +        cmd->resp.code = VIRTIO_SND_S_BAD_MSG;
> +    }
> +
> +    iov_from_buf(cmd->elem->in_sg,
> +                 cmd->elem->in_num,
> +                 0,
> +                 &cmd->resp,
> +                 sizeof(cmd->resp));
> +    virtqueue_push(cmd->vq, cmd->elem, sizeof(cmd->elem));
> +    virtio_notify(VIRTIO_DEVICE(s), cmd->vq);
> +    cmd->finished = true;
> +}
> +
> +/*
> + * Consume all elements in command queue.
> + *
> + * @s: VirtIOSound device
> + */
> +static void virtio_snd_process_cmdq(VirtIOSound *s)
> +{
> +    virtio_snd_ctrl_command *cmd;
> +
> +    if (unlikely(qatomic_read(&s->processing_cmdq))) {
> +        return;
> +    }
> +
> +    WITH_QEMU_LOCK_GUARD(&s->cmdq_mutex) {
> +        qatomic_set(&s->processing_cmdq, true);
> +        while (!QTAILQ_EMPTY(&s->cmdq)) {
> +            cmd = QTAILQ_FIRST(&s->cmdq);
> +
> +            /* process command */
> +            process_cmd(s, cmd);
> +
> +            QTAILQ_REMOVE(&s->cmdq, cmd, next);
> +
> +            g_free(cmd);
> +        }
> +        qatomic_set(&s->processing_cmdq, false);
> +    }
> +}
> +
> +/*
> + * The control message handler. Pops an element from the control virtqueue,
> + * and stores them to VirtIOSound's cmdq queue and finally calls
> + * virtio_snd_process_cmdq() for processing.
> + *
> + * @vdev: VirtIOSound device
> + * @vq: Control virtqueue
> + */
> +static void virtio_snd_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    VirtIOSound *s = VIRTIO_SND(vdev);
> +    VirtQueueElement *elem;
> +    virtio_snd_ctrl_command *cmd;
> +
> +    trace_virtio_snd_handle_ctrl(vdev, vq);
> +
> +    if (!virtio_queue_ready(vq)) {
> +        return;
> +    }
> +
> +    elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> +    while (elem) {
> +        cmd = g_new0(virtio_snd_ctrl_command, 1);
> +        cmd->elem = elem;
> +        cmd->vq = vq;
> +        cmd->finished = false;
> +        cmd->resp.code = VIRTIO_SND_S_OK;
> +        QTAILQ_INSERT_TAIL(&s->cmdq, cmd, next);
> +        elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> +    }
> +
> +    virtio_snd_process_cmdq(s);
> +}
> +
> +/*
> + * The event virtqueue handler.
> + * Not implemented yet.
> + *
> + * @vdev: VirtIOSound device
> + * @vq: event vq
> + */
> +static void virtio_snd_handle_event(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    qemu_log_mask(LOG_UNIMP, "virtio_snd: event queue is unimplemented.");
> +    trace_virtio_snd_handle_event();
> +}
> +
> +/*
> + * The tx virtqueue handler. Makes the buffers available to their respective
> + * streams for consumption.
> + *
> + * @vdev: VirtIOSound device
> + * @vq: tx virtqueue
> + */
> +static void virtio_snd_handle_xfer(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    VirtIOSound *s = VIRTIO_SND(vdev);
> +    VirtIOSoundPCMStream *stream = NULL;
> +    VirtQueueElement *elem;
> +    size_t sz;
> +    virtio_snd_pcm_xfer hdr;
> +    virtio_snd_pcm_status resp = { 0 };
> +
> +    trace_virtio_snd_handle_xfer();
> +
> +    for (;;) {
> +        elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> +        if (!elem) {
> +            break;
> +        }
> +        /* get the message hdr object */
> +        sz = iov_to_buf(elem->out_sg,
> +                        elem->out_num,
> +                        0,
> +                        &hdr,
> +                        sizeof(hdr));
> +        if (sz != sizeof(hdr)
> +            || hdr.stream_id >= s->snd_conf.streams
> +            || !s->pcm->streams[hdr.stream_id]) {
> +            goto tx_err;
> +        }
> +
> +        stream = s->pcm->streams[hdr.stream_id];
> +        if (stream->direction == VIRTIO_SND_D_INPUT) {
> +            goto tx_err;
> +        }
> +
> +        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> +            virtio_snd_pcm_read_write(stream,
> +                    vq,
> +                    elem,
> +                    hdr.stream_id == VIRTIO_SND_D_INPUT);
> +
> +            resp.status = VIRTIO_SND_S_OK;
> +            iov_from_buf(elem->in_sg,
> +                         elem->in_num,
> +                         0,
> +                         &resp,
> +                         sizeof(resp));
> +        }
> +        continue;
> +
> +tx_err:
> +        WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> +            resp.status = VIRTIO_SND_S_BAD_MSG;
> +            iov_from_buf(elem->in_sg,
> +                         elem->in_num,
> +                         0,
> +                         &resp,
> +                         sizeof(resp));
> +        }
> +    }
> +
> +    /*
> +     * Notify vq about virtio_snd_pcm_status responses.
> +     * Buffer responses must be notified separately later.
> +     */
> +    virtio_notify(VIRTIO_DEVICE(s), vq);
> +}
> +
> +static uint64_t get_features(VirtIODevice *vdev, uint64_t features,
> +                             Error **errp)
> +{
> +    /*
> +     * virtio-v1.2-csd01, 5.14.3,
> +     * Feature Bits
> +     * None currently defined.
> +     */
> +    trace_virtio_snd_get_features(vdev, features);
> +    return features | 1UL << VIRTIO_F_VERSION_1 | 1UL << VIRTIO_F_IN_ORDER;
> +}
> +
> +static void virtio_snd_set_pcm(VirtIOSound *snd)
> +{
> +    VirtIOSoundPCM *pcm;
> +
> +    pcm = g_new0(VirtIOSoundPCM, 1);
> +    pcm->snd = snd;
> +
> +    pcm->streams = g_new0(VirtIOSoundPCMStream *, snd->snd_conf.streams);
> +    pcm->pcm_params = g_new0(VirtIOSoundPCMParams *, snd->snd_conf.streams);
> +    pcm->jacks = g_new0(struct virtio_snd_jack *, snd->snd_conf.jacks);
> +
> +    snd->pcm = pcm;
> +
> +    return;
> +}
> +
> +void virtio_snd_common_realize(DeviceState *dev,
> +                               VirtIOHandleOutput ctrl,
> +                               VirtIOHandleOutput evt,
> +                               VirtIOHandleOutput txq,
> +                               VirtIOHandleOutput rxq,
> +                               Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VirtIOSound *vsnd = VIRTIO_SND(dev);
> +    virtio_snd_pcm_set_params default_params;
> +    uint32_t status;
> +
> +    virtio_snd_set_pcm(vsnd);
> +
> +    virtio_init(vdev, VIRTIO_ID_SOUND, sizeof(virtio_snd_config));
> +
> +    /* set number of jacks and streams */
> +    if (vsnd->snd_conf.jacks > 8) {
> +        error_setg(errp,
> +                   "Invalid number of jacks: %d",

"%u"

> +                   vsnd->snd_conf.jacks);
> +        return;
> +    }
> +    if (vsnd->snd_conf.streams < 1 || vsnd->snd_conf.streams > 10) {
> +        error_setg(errp,
> +                   "Invalid number of streams: %d",

"%u"

> +                    vsnd->snd_conf.streams);
> +        return;
> +    }
> +
> +    if (vsnd->snd_conf.chmaps > VIRTIO_SND_CHMAP_MAX_SIZE) {
> +        error_setg(errp,
> +                   "Invalid number of channel maps: %d",

"%u"

> +                   vsnd->snd_conf.chmaps);
> +        return;
> +    }
> +
> +    AUD_register_card("virtio-sound", &vsnd->card);
> +
> +    /* set default params for all streams */
> +    default_params.features = 0;
> +    default_params.buffer_bytes = 8192;
> +    default_params.period_bytes = 4096;
> +    default_params.channels = 2;
> +    default_params.format = VIRTIO_SND_PCM_FMT_S16;
> +    default_params.rate = VIRTIO_SND_PCM_RATE_44100;
> +
> +    vsnd->queues[VIRTIO_SND_VQ_CONTROL] = virtio_add_queue(vdev, 64, ctrl);
> +    vsnd->queues[VIRTIO_SND_VQ_EVENT] = virtio_add_queue(vdev, 64, evt);
> +    vsnd->queues[VIRTIO_SND_VQ_TX] = virtio_add_queue(vdev, 64, txq);
> +    vsnd->queues[VIRTIO_SND_VQ_RX] = virtio_add_queue(vdev, 64, rxq);
> +    qemu_mutex_init(&vsnd->cmdq_mutex);
> +    QTAILQ_INIT(&vsnd->cmdq);
> +
> +    for (int i = 0; i < vsnd->snd_conf.streams; i++) {
> +        default_params.hdr.stream_id = i;
> +        status = virtio_snd_pcm_set_params_impl(vsnd, &default_params);
> +        if (status != VIRTIO_SND_S_OK) {
> +            error_setg(errp,
> +                       "Can't initalize stream params, device responded with %s.",
> +                       print_code(status));
> +            return;
> +        }
> +        status = virtio_snd_pcm_prepare_impl(vsnd, i);
> +        if (status != VIRTIO_SND_S_OK) {
> +            error_setg(errp,
> +                       "Can't prepare streams, device responded with %s.",
> +                       print_code(status));
> +            return;
> +        }
> +    }
> +}
> +
> +static void
> +virtio_snd_vm_state_change(void *opaque, bool running, RunState state)

'state' argument is not used, remove it.

> +{
> +    if (running) {
> +        trace_virtio_snd_vm_state_running();
> +    } else {
> +        trace_virtio_snd_vm_state_stopped();
> +    }
> +}
> +
> +static void virtio_snd_realize(DeviceState *dev, Error **errp)
> +{
> +    VirtIOSound *vsnd = VIRTIO_SND(dev);
> +    Error *err = NULL;
> +
> +    vsnd->pcm = NULL;
> +    vsnd->vmstate =
> +        qemu_add_vm_change_state_handler(virtio_snd_vm_state_change, vsnd);
> +
> +    trace_virtio_snd_realize(vsnd);
> +
> +    virtio_snd_common_realize(dev,
> +                              virtio_snd_handle_ctrl,
> +                              virtio_snd_handle_event,
> +                              virtio_snd_handle_xfer,
> +                              virtio_snd_handle_xfer,
> +                              &err);
> +    if (err != NULL) {
> +        error_propagate(errp, err);
> +        return;
> +    }
> +}
> +
> +/*
> + * AUD_* output callback.
> + *
> + * @data: VirtIOSoundPCMStream stream
> + * @available: number of bytes that can be written with AUD_write()
> + */
> +static void virtio_snd_pcm_out_cb(void *data, int available)
> +{
> +    VirtIOSoundPCMStream *stream = data;
> +    VirtIOSoundPCMBlock *block;
> +    VirtIOSoundPCMBlock *next;
> +    int size;
> +
> +    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> +        QSIMPLEQ_FOREACH_SAFE(block, &stream->queue, entry, next) {
> +            for (;;) {
> +                size = MIN(block->size, available);
> +                size = AUD_write(stream->voice.out,
> +                        block->data + block->offset,
> +                        size);
> +                block->size -= size;
> +                block->offset += size;
> +                if (!block->size) {
> +                    virtqueue_push(block->vq,
> +                            block->elem,
> +                            sizeof(block->elem));
> +                    virtio_notify(VIRTIO_DEVICE(stream->s),
> +                            block->vq);
> +                    QSIMPLEQ_REMOVE_HEAD(&stream->queue, entry);
> +                    g_free(block);
> +                    available -= size;
> +                    break;
> +                }
> +
> +                available -= size;
> +                if (!available) {
> +                    break;
> +                }
> +            }
> +            if (!available) {
> +                break;
> +            }
> +        }
> +    }
> +}
> +
> +/*
> + * Flush all buffer data from this stream's queue into the driver's virtual
> + * queue.
> + *
> + * @stream: VirtIOSoundPCMStream *stream
> + */
> +static void virtio_snd_pcm_flush(VirtIOSoundPCMStream *stream)
> +{
> +    VirtIOSoundPCMBlock *block;
> +    VirtIOSoundPCMBlock *next;
> +
> +    WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> +        QSIMPLEQ_FOREACH_SAFE(block, &stream->queue, entry, next) {
> +            AUD_write(stream->voice.out, block->data, block->size);
> +            virtqueue_push(block->vq, block->elem, sizeof(block->elem));
> +            virtio_notify(VIRTIO_DEVICE(stream->s), block->vq);
> +            QSIMPLEQ_REMOVE(&stream->queue, block, VirtIOSoundPCMBlock, entry);
> +        }
> +    }
> +}
> +
> +/*
> + * Close the sound card.
> + *
> + * @stream: VirtIOSoundPCMStream *stream
> + */
> +static void virtio_snd_pcm_close(VirtIOSoundPCMStream *stream)
> +{
> +    virtio_snd_process_cmdq(stream->s);
> +    if (stream->direction == VIRTIO_SND_D_OUTPUT) {
> +        AUD_close_out(&stream->pcm->snd->card, stream->voice.out);
> +        stream->voice.out = NULL;
> +    } else {
> +        AUD_close_in(&stream->pcm->snd->card, stream->voice.in);
> +        stream->voice.in = NULL;
> +    }
> +
> +}
> +
> +static void virtio_snd_unrealize(DeviceState *dev)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VirtIOSound *vsnd = VIRTIO_SND(dev);
> +    VirtIOSoundPCMStream *stream;
> +
> +    qemu_del_vm_change_state_handler(vsnd->vmstate);
> +    virtio_del_queue(vdev, 0);
> +
> +    trace_virtio_snd_unrealize(vsnd);
> +
> +    for (int i = VIRTIO_SND_D_OUTPUT; i <= VIRTIO_SND_D_INPUT; i++) {
> +        stream = vsnd->pcm->streams[i];
> +        virtio_snd_pcm_close(stream);
> +        g_free(stream);
> +    }
> +
> +    AUD_remove_card(&vsnd->card);
> +    g_free(vsnd->pcm);
> +    virtio_cleanup(vdev);
> +}
> +
> +
> +static uint32_t
> +virtio_snd_pcm_read_write(VirtIOSoundPCMStream *stream,
> +                          VirtQueue *vq,
> +                          VirtQueueElement *element,
> +                          bool read)
> +{
> +    VirtIOSoundPCMBlock *fragment;
> +    size_t size = iov_size(element->out_sg, element->out_num) -
> +        sizeof(virtio_snd_pcm_xfer);
> +
> +    fragment = g_malloc0(sizeof(VirtIOSoundPCMBlock) + size);
> +    fragment->elem = element;
> +    fragment->vq = vq;
> +    fragment->size = size;
> +    fragment->offset = 0;
> +
> +    iov_to_buf(element->out_sg, element->out_num,
> +               sizeof(virtio_snd_pcm_xfer),
> +               fragment->data,
> +               size);
> +
> +    QSIMPLEQ_INSERT_TAIL(&stream->queue, fragment, entry);
> +
> +    return fragment->size;
> +}
> +
> +static void virtio_snd_reset(VirtIODevice *vdev)
> +{
> +    VirtIOSound *s = VIRTIO_SND(vdev);
> +    virtio_snd_ctrl_command *cmd;
> +
> +    WITH_QEMU_LOCK_GUARD(&s->cmdq_mutex) {
> +        while (!QTAILQ_EMPTY(&s->cmdq)) {
> +            cmd = QTAILQ_FIRST(&s->cmdq);
> +            QTAILQ_REMOVE(&s->cmdq, cmd, next);
> +            g_free(cmd);
> +        }
> +    }
> +}
> +
> +static void virtio_snd_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> +
> +
> +    set_bit(DEVICE_CATEGORY_SOUND, dc->categories);
> +    device_class_set_props(dc, virtio_snd_properties);
> +
> +    dc->vmsd = &vmstate_virtio_snd;
> +    vdc->vmsd = &vmstate_virtio_snd_device;
> +    vdc->realize = virtio_snd_realize;
> +    vdc->unrealize = virtio_snd_unrealize;
> +    vdc->get_config = virtio_snd_get_config;
> +    vdc->set_config = virtio_snd_set_config;
> +    vdc->get_features = get_features;
> +    vdc->reset = virtio_snd_reset;
> +    vdc->legacy_features = 0;
> +}
> +
> +static const TypeInfo virtio_snd_info = {
> +    .name          = TYPE_VIRTIO_SND,
> +    .parent        = TYPE_VIRTIO_DEVICE,
> +    .instance_size = sizeof(VirtIOSound),
> +    .class_init    = virtio_snd_class_init,
> +};
> +
> +static void virtio_snd_register(void)
> +{
> +    type_register_static(&virtio_snd_info);

Preferably use DEFINE_TYPES().

> +}
> +
> +type_init(virtio_snd_register);
> diff --git a/include/hw/virtio/virtio-snd.h b/include/hw/virtio/virtio-snd.h
> new file mode 100644
> index 0000000000..c19e71f40f
> --- /dev/null
> +++ b/include/hw/virtio/virtio-snd.h
> @@ -0,0 +1,194 @@
> +/*
> + * VIRTIO Sound Device conforming to
> + *
> + * "Virtual I/O Device (VIRTIO) Version 1.2
> + * Committee Specification Draft 01
> + * 09 May 2022"
> + *
> + * Copyright (c) 2023 Emmanouil Pitsidianakis <manos.pitsidianakis@linaro.org>
> + * Copyright (C) 2019 OpenSynergy GmbH
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * (at your option) any later version.  See the COPYING file in the
> + * top-level directory.
> + */
> +
> +#ifndef QEMU_VIRTIO_SOUND_H
> +#define QEMU_VIRTIO_SOUND_H
> +
> +#include "hw/virtio/virtio.h"
> +#include "audio/audio.h"
> +#include "standard-headers/linux/virtio_ids.h"
> +#include "standard-headers/linux/virtio_snd.h"

By moving the forward declarations [*] here, ...

> +
> +#define TYPE_VIRTIO_SND "virtio-sound-device"
> +#define VIRTIO_SND(obj) \
> +        OBJECT_CHECK(VirtIOSound, (obj), TYPE_VIRTIO_SND)
> +
> +typedef struct VirtIOSound {
> +    VirtIODevice parent_obj;
> +    struct VirtQueue *queues[VIRTIO_SND_VQ_MAX];
> +    struct VirtIOSoundPCM *pcm;
> +    bool virtio_access_is_big_endian;
> +    QEMUSoundCard card;
> +    VMChangeStateEntry *vmstate;
> +    char *audiodev;
> +    struct virtio_snd_config snd_conf;
> +    QemuMutex cmdq_mutex;
> +    QTAILQ_HEAD(, virtio_snd_ctrl_command) cmdq;
> +    bool processing_cmdq;
> +} VirtIOSound;
> +
> +typedef struct virtio_snd_ctrl_command {
> +    struct VirtQueueElement *elem;
> +    struct VirtQueue *vq;
> +    struct virtio_snd_hdr ctrl;
> +    struct virtio_snd_hdr resp;

... you can use them here. No need for 'struct' (neither for VirtQueue*)

> +    bool finished;
> +    QTAILQ_ENTRY(virtio_snd_ctrl_command) next;
> +} virtio_snd_ctrl_command;
> +
> +#define VIRTIO_SND_FILL_CMD(out) do {                                   \
> +        size_t s;                                                       \
> +        s = iov_to_buf(cmd->elem->out_sg, cmd->elem->out_num, 0,        \
> +                       &out, sizeof(out));                              \
> +        if (s != sizeof(out)) {                                         \
> +            qemu_log_mask(LOG_GUEST_ERROR,                              \
> +                          "%s: virtio-snd command size incorrect %zu vs \
> +                          %zu\n", __func__, s, sizeof(out));            \
> +            return;                                                     \
> +        }                                                               \
> +    } while (0)
> +
> +/* CONFIGURATION SPACE */
> +
> +typedef struct virtio_snd_config virtio_snd_config;
> +
> +/* COMMON DEFINITIONS */
> +

[*]

> +/* common header for request/response*/
> +typedef struct virtio_snd_hdr virtio_snd_hdr;
> +
> +/* event notification */
> +typedef struct virtio_snd_event virtio_snd_event;
> +
> +/* common control request to query an item information */
> +typedef struct virtio_snd_query_info virtio_snd_query_info;
> +
> +/* JACK CONTROL MESSAGES */
> +
> +typedef struct virtio_snd_jack_hdr virtio_snd_jack_hdr;
> +
> +/* jack information structure */
> +typedef struct virtio_snd_jack_info virtio_snd_jack_info;
> +
> +/* jack remapping control request */
> +typedef struct virtio_snd_jack_remap virtio_snd_jack_remap;
> +
> +/*
> + * PCM CONTROL MESSAGES
> + */
> +typedef struct virtio_snd_pcm_hdr virtio_snd_pcm_hdr;
> +
> +/* PCM stream info structure */
> +typedef struct virtio_snd_pcm_info virtio_snd_pcm_info;
> +
> +/* set PCM stream params */
> +typedef struct virtio_snd_pcm_set_params virtio_snd_pcm_set_params;
> +
> +/* I/O request header */
> +typedef struct virtio_snd_pcm_xfer virtio_snd_pcm_xfer;
> +
> +/* I/O request status */
> +typedef struct virtio_snd_pcm_status virtio_snd_pcm_status;
> +
> +/* Stream params */
> +typedef struct VirtIOSoundPCMParams {
> +    uint32_t features;
> +    uint32_t buffer_bytes;          /* size of hardware buffer in bytes */
> +    uint32_t period_bytes;          /* size of hardware period in bytes */
> +    uint8_t channels;
> +    uint8_t format;
> +    uint8_t rate;
> +} VirtIOSoundPCMParams;
> +
> +#define VIRTIO_SND_PCM_MIN_CHANNELS     2
> +
> +typedef struct VirtIOSoundPCMBlock VirtIOSoundPCMBlock;
> +typedef struct VirtIOSoundPCM VirtIOSoundPCM;
> +
> +struct VirtIOSoundPCMBlock {
> +    QSIMPLEQ_ENTRY(VirtIOSoundPCMBlock) entry;
> +    struct VirtQueueElement *elem;
> +    struct VirtQueue *vq;

(use typedef, drop the 'struct')

> +    int size;

size_t surely.

> +    int offset;

unsigned?

> +    uint8_t data[];
> +};
> +
> +typedef struct VirtIOSoundPCMStream {
> +    VirtIOSoundPCM *pcm;
> +    struct virtio_snd_pcm_info info;
> +    uint32_t id;
> +    uint32_t buffer_bytes;
> +    uint32_t period_bytes;
> +    /* channel position values (VIRTIO_SND_CHMAP_XXX) */
> +    uint8_t positions[VIRTIO_SND_CHMAP_MAX_SIZE];
> +    VirtIOSound *s;
> +    uint32_t features; /* 1 << VIRTIO_SND_PCM_F_XXX */
> +    uint64_t formats; /* 1 << VIRTIO_SND_PCM_FMT_XXX */
> +    uint64_t rates; /* 1 << VIRTIO_SND_PCM_RATE_XXX */
> +    uint8_t direction;
> +    uint8_t channels_min;
> +    uint8_t channels_max;
> +    bool flushing;
> +    struct audsettings as;
> +    struct audsettings desired_as;
> +    union {
> +        SWVoiceIn *in;
> +        SWVoiceOut *out;
> +    } voice;
> +    QemuMutex queue_mutex;
> +    QSIMPLEQ_HEAD(, VirtIOSoundPCMBlock) queue;
> +} VirtIOSoundPCMStream;
> +
> +struct VirtIOSoundPCM {
> +    VirtIOSound *snd;
> +    struct VirtIOSoundPCMParams **pcm_params;
> +    VirtIOSoundPCMStream **streams;
> +    struct virtio_snd_jack **jacks;
> +};
> +
> +void virtio_snd_common_realize(DeviceState *dev,
> +                               VirtIOHandleOutput ctrl,
> +                               VirtIOHandleOutput evt,
> +                               VirtIOHandleOutput txq,
> +                               VirtIOHandleOutput rxq,
> +                               Error **errp);
> +
> +static inline const char *print_code(int code)

code is uint32_t.

No need to inline (only used in virtio-snd.c, move there).

> +{
> +  switch (code) {
> +  case VIRTIO_SND_R_JACK_INFO:
> +    return "VIRTIO_SND_R_JACK_INFO";
> +  case VIRTIO_SND_R_JACK_REMAP:
> +    return "VIRTIO_SND_R_JACK_REMAP";
> +  case VIRTIO_SND_R_PCM_INFO:
> +    return "VIRTIO_SND_R_PCM_INFO";
> +  case VIRTIO_SND_R_PCM_SET_PARAMS:
> +    return "VIRTIO_SND_R_PCM_SET_PARAMS";
> +  case VIRTIO_SND_R_PCM_PREPARE:
> +    return "VIRTIO_SND_R_PCM_PREPARE";
> +  case VIRTIO_SND_R_PCM_RELEASE:
> +    return "VIRTIO_SND_R_PCM_RELEASE";
> +  case VIRTIO_SND_R_PCM_START:
> +    return "VIRTIO_SND_R_PCM_START";
> +  case VIRTIO_SND_R_PCM_STOP:
> +    return "VIRTIO_SND_R_PCM_STOP";
> +  case VIRTIO_SND_R_CHMAP_INFO:
> +    return "VIRTIO_SND_R_CHMAP_INFO";
> +  default:
> +    return "invalid code";
> +  }
> +};
> +#endif