Re: [PATCH v8 11/12] virtio-sound: implement audio capture (RX)

[Volker Rümelin]

Am 28.08.23 um 21:55 schrieb Emmanouil Pitsidianakis:
> To perform audio capture we duplicate the TX logic of the previous
> commit with the following difference: we receive data from the QEMU
> audio backend and write it in the virt queue IO buffers the guest sends
> to QEMU. When they are full (i.e. they have `period_bytes` amount of
> data) or when recording stops in QEMU's audio backend, the buffer is
> returned to the guest by notifying it.
>
> Signed-off-by: Emmanouil Pitsidianakis <manos.pitsidianakis@linaro.org>
> ---
>   hw/virtio/trace-events |   3 +-
>   hw/virtio/virtio-snd.c | 245 +++++++++++++++++++++++++++++++++++------
>   2 files changed, 215 insertions(+), 33 deletions(-)
>
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 3b95e745c2..9b7fbffedc 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -172,4 +172,5 @@ virtio_snd_handle_code(uint32_t val, const char *code) "ctrl 
> code msg val = %"PR
>   virtio_snd_handle_chmap_info(void) "VIRTIO_SND_CHMAP_INFO called"
>   virtio_snd_handle_event(void) "event queue callback called"
>   virtio_snd_pcm_stream_flush(uint32_t stream) "flushing stream %"PRIu32
> -virtio_snd_handle_xfer(void) "tx/rx queue callback called"
> +virtio_snd_handle_tx_xfer(void) "tx queue callback called"
> +virtio_snd_handle_rx_xfer(void) "rx queue callback called"
> diff --git a/hw/virtio/virtio-snd.c b/hw/virtio/virtio-snd.c
> index 4859ce4bf6..70e8a73072 100644
> --- a/hw/virtio/virtio-snd.c
> +++ b/hw/virtio/virtio-snd.c

> @@ -1002,26 +1073,119 @@ static void virtio_snd_pcm_out_cb(void *data, int 
> available)
>   }
>   
>   /*
> - * Flush all buffer data from this stream's queue into the driver's virtual
> - * queue.
> + * AUD_* input callback.
>    *
> - * @stream: VirtIOSoundPCMStream *stream
> + * @data: VirtIOSoundPCMStream stream
> + * @available: number of bytes that can be read with AUD_read()
>    */
> -static void virtio_snd_pcm_flush(VirtIOSoundPCMStream *stream)
> +static void virtio_snd_pcm_in_cb(void *data, int available)
>   {
> +    VirtIOSoundPCMStream *stream = data;
>       VirtIOSoundPCMBlock *block;
> -    VirtIOSoundPCMBlock *next;
> +    uint32_t sz;
> +    virtio_snd_pcm_status resp = { 0 };
> +    size_t size;
>   
>       WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
> -        QSIMPLEQ_FOREACH_SAFE(block, &stream->queue, entry, next) {
> -            AUD_write(stream->voice.out, block->data + block->offset, 
> 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);
> +        while (!QSIMPLEQ_EMPTY(&stream->queue)) {
> +            block = QSIMPLEQ_FIRST(&stream->queue);
> +
> +            for (;;) {
> +                size = AUD_read(stream->voice.in,
> +                        block->data + block->offset,
> +                        MIN(stream->period_bytes - block->offset, available));

For the -audiodev in.mixing-engine=off case, 'available' is much larger 
than the available bytes AUD_read() can actually read. 'size' is 0 when 
the upstream buffer is empty.

+                if (size == 0) {
+                    available = 0;
+                    break;
+                }

This fixes audio recording with -audiodev 
pipewire,out.mixing-engine=off,in.mixing-engine=off,id=audio0. The issue 
with two wrong audio frames every 25ms remains.

> +                block->offset += size;
> +                block->size += size;
> +                if (size == 0 || block->size >= stream->period_bytes) {

-                if (size == 0 || block->size >= stream->period_bytes) {
+                if (block->size >= stream->period_bytes) {

With best regards,
Volker

> +                    resp.status = VIRTIO_SND_S_OK;
> +                     sz = iov_from_buf(block->elem->in_sg,
> +                                  block->elem->in_num,
> +                                  0,
> +                                  &resp,
> +                                  sizeof(resp));
> +
> +                    /* Copy data -if any- to guest */
> +                    if (block->size) {
> +                        iov_from_buf(block->elem->in_sg,
> +                                     block->elem->in_num,
> +                                     sz,
> +                                     block->data,
> +                                     MIN(stream->period_bytes, 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;
> +            }
>           }
>       }
>   }
>