[BUG?] Setting (start_threshold > stop_threshold) makes snd_pcm_writei(a_small_buffer) XRUN immediately

[Zhang Boyang]

Hello,

   I'm using ALSA to develop an audio-streaming application. I try to 
use start_threshold and stop_threshold in combination with small 
buffers. However, I think I probably found a bug about this.
   I'm setting start_threshold=100 and stop_threshold=50. I'm also using 
a buffer of 44 frames. When I call 
snd_pcm_writei(the_small_44_frames_buffer), pcm state came to XRUN from 
PREPARED directly. I think this is a bug because the stream hasn't 
started. It's hard to say a xrun occurred while stream not started.
   I'm wondering if this is a ALSA-bug or a misuse of ALSA. A simple bug 
test program is attached.
   Thank you very much!

Zhang Boyang

p.s.
   I dug into kernel code. After writting hardware buffer, 
__snd_pcm_lib_xfer() called snd_pcm_update_state(), which set the XRUN 
state.
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