Re: [PATCH] audio: fix audio recording

["Zoltán Kővágó" <dirty.ice.hu@gmail.com>]

On 2019-11-19 20:43, Richard Henderson wrote:
> On 11/19/19 9:01 AM, Philippe Mathieu-Daudé wrote:
>> Cc'ing Zoltán.
>>
>> On 11/19/19 7:58 AM, Volker Rümelin wrote:
>>> With current code audio recording with all audio backends
>>> except PulseAudio and DirectSound is broken. The generic audio
>>> recording buffer management forgot to update the current read
>>> position after a read.
>>>
>>> Fixes: ff095e5231 "audio: api for mixeng code free backends"
>>>
>>> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
>>> ---
>>>    audio/audio.c | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/audio/audio.c b/audio/audio.c
>>> index 7fc3aa9d16..56fae55047 100644
>>> --- a/audio/audio.c
>>> +++ b/audio/audio.c
>>> @@ -1390,6 +1390,7 @@ void *audio_generic_get_buffer_in(HWVoiceIn *hw, size_t
>>> *size)
>>>            size_t read = hw->pcm_ops->read(hw, hw->buf_emul + hw->pos_emul,
>>>                                            read_len);
>>>            hw->pending_emul += read;
>>> +        hw->pos_emul = (hw->pos_emul + read) % hw->size_emul;
>>
>> Anyway since read() can return a negative value, both previous assignments
>> should go after this if/break check...
> 
> This isn't read(2).
> 
>      size_t (*read)    (HWVoiceIn *hw, void *buf, size_t size);
> 
> Since this isn't ssize_t, no negative return value possible.

Yes, read failures are handled inside the backends.  If the backend 
really can't read anything, it'll return zero, which is harmless here.

Zoltan