Re: [Qemu-devel] [PATCH 20/25] audio: remove mixeng specific code from backends

[Gerd Hoffmann <kraxel@redhat.com>]

On Do, 2015-08-06 at 20:28 +0200, Kővágó, Zoltán wrote:
> Backends no longer have to deal with mixeng, they just receive a buffer
> in the correct sample format, all mixeng logic is now in the audio.c
> (and mixeng.c).  Backends also do not have to deal with soft voices.
> 
> Backends now have two way to read/write sound:
> * write and read functions: similar to old read/write functions, except
>   that they actually read/write the data to the backend instead of
>   placing it into the mixeng buffer.  You no longer need run_in/run_out
>   afterwards.
> * get_buffer_out/put_buffer_out: the first function returns a buffer
>   that can hold some audio data.  The caller fills this buffer (maybe
>   partially) and calls put_buffer to actually write the data.  This way
>   we can save copying the buffer in some cases (for example mmaped
>   audio).  Similarly there's get_buffer_in/put_buffer_in for reading.
> 
> Backends only have to support one access method, but they can support
> both if they have efficient implementation for both cases.

Phew, this one became pretty big.  Could this be splitted up?  The
s/int/size_t/ should be easy to separate.

Also having individual patches for individual backends would be nice.
Possibly you can first add the new interfaces, & helper functions, then
switch backends over one by one, hooking the generic
audio_pcm_hw_run_out() function into run_out callback, finally remove
the old interfaces and call audio_pcm_hw_run_out directly.

cheers,
  Gerd