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

[Geoffrey McRae]

On 2020-05-12 00:53, Stefan Hajnoczi wrote:
> 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 <address@hidden>
> > ---
> >  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 now use the ICH9 device, however, I had buffer size issues with 
usbaudio.

> 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?

Sure.

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

Nope, left behind from a prior implementation, I will remove it.