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

[Geoffrey McRae <geoff@hostfission.com>]

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 <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 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.