Re: [PATCH v8] audio/jack: add JACK client audiodev

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Wed, Apr 29, 2020 at 03:53:58PM +1000, Geoffrey McRae wrote:
> This commit adds a new audiodev backend to allow QEMU to use JACK as
> both an audio sink and source.
> 
> Signed-off-by: Geoffrey McRae <geoff@hostfission.com>
> ---
>  audio/Makefile.objs    |   5 +
>  audio/audio.c          |   1 +
>  audio/audio_template.h |   2 +
>  audio/jackaudio.c      | 677 +++++++++++++++++++++++++++++++++++++++++
>  configure              |  17 ++
>  qapi/audio.json        |  56 +++-
>  6 files changed, 756 insertions(+), 2 deletions(-)
>  create mode 100644 audio/jackaudio.c

Cool! Out of interest, which emulated audio device do you use and have
you had issues with buffer sizes/latency?

I haven't reviewed in depth but in general this looks good.

> +typedef struct QJackBuffer {
> +    int          channels;
> +    int          frames;
> +    _Atomic(int) used;

stdatomic.h isn't used directly in QEMU. Can you use "qemu/atomic.h"
instead?

> +static inline int qjack_buffer_used(QJackBuffer *buffer)
> +{
> +    assert(buffer->data);
> +    return atomic_load_explicit(&buffer->used, memory_order_relaxed);
> +}

Is this function used?

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