[alsa-devel] [Pkg-alsa-devel] Bug#438118: alsa-utils: aplay non-blocking mode isn't working

Anders Boström anders at netinsight.se
Thu Sep 27 14:16:29 CEST 2007

>>>>> "TI" == Takashi Iwai <tiwai at suse.de> writes:

 TI> At Tue, 18 Sep 2007 09:41:48 +0200 (CEST),
 TI> Anders Boström wrote:
 >> >>>>> "TI" == Takashi Iwai <tiwai at suse.de> writes:
 >> >> can one please have a lokk at this? aplay -N isn't working for the
 >> >> OP.
 TI> Cannot reproduce here.  Could you _post_ more details?
 >> OK, I've tested more, and discovered that the problem seems to be that
 >> the end of the sound is cut in non-blocking mode. And if I play a very
 >> short sound-file, I can't hear anything. Blocking mode works fine.
 >> When using non-blocking mode, an strace contains "ioctl(4, 0x4144,
 >> 0x2b9f785d8000)        = -1 EAGAIN (Resource temporarily
 >> unavailable)". Blocking mode never contains the EAGAIN response.
 >> I attach two files. When playing halt.au, I can only hear the start,
 >> about as much as "ha". When playing metal.au, I can't hear anything.

 TI> OK, thanks, I see the problem now.

 TI> I don't remember whether it's a feature or a bug.  The drain ioctl
 TI> rejects the non-block mode.

I can understand the idea here, that in non-blocking mode, no call
should block, ever. But on the other hand, if you call the drain
ioctl, you probably expect it to work, even in non-blocking mode. Why
would you otherwise call it?

 TI> Anyway, a simple patch is below.  Let me know if it works.

It works fine! Thanks!

/ Anders

 TI> diff -r 0028e39ead78 core/pcm_native.c
 TI> --- a/core/pcm_native.c	Tue Sep 18 00:52:38 2007 +0200
 TI> +++ b/core/pcm_native.c	Tue Sep 18 17:44:31 2007 +0200
 TI> @@ -1368,8 +1368,6 @@ static int snd_pcm_prepare(struct snd_pc
 TI>  static int snd_pcm_pre_drain_init(struct snd_pcm_substream *substream, int state)
 TI>  {
 TI> -	if (substream->f_flags & O_NONBLOCK)
 TI> -		return -EAGAIN;
 substream-> runtime->trigger_master = substream;
 TI>  	return 0;
 TI>  }

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