Re: possible ALSA bug/feature (was: important recording broke. why?) (fwd)

[Takashi Iwai <tiwai@suse.de>]

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At Fri, 21 Mar 2003 16:16:04 +0200 (EET),
Kai Vehmanen wrote:
> 
> Hi,
> 
> first please read the mail to ecasound-list below. 
> 
> It seems that with newer ALSA versions, snd_pcm_read[in]()  sometimes
> returns -EIO even though documentation says nothing about this. After some
> testing this seems to not happen on direct hw-access, only with
> the pcm_plugin. The EIO comes from snd_pcm_wait(). 
> 
> Is this a bug or or a feature?

i also don't know whether Jaroslav added as a feature or as an
unexpected bug.  anyway, this means that the poll failed and the pcm
status is abnormal, typically xruns...

how about the attached patch?  (untested)


Takashi

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Index: alsa-lib/src/pcm/pcm.c
===================================================================
RCS file: /suse/tiwai/cvs/alsa/alsa-lib/src/pcm/pcm.c,v
retrieving revision 1.130
diff -u -r1.130 pcm.c
--- alsa-lib/src/pcm/pcm.c	20 Mar 2003 11:06:13 -0000	1.130
+++ alsa-lib/src/pcm/pcm.c	25 Mar 2003 18:00:13 -0000
@@ -6110,9 +6110,15 @@
 			}
 
 			err = snd_pcm_wait(pcm, -1);
-			if (err < 0)
-				break;
 			state = snd_pcm_state(pcm);
+			if (err < 0) {
+				/* check more precisely */
+				if (state == SND_PCM_STATE_XRUN)
+					err = -EPIPE;
+				else if (state == SND_PCM_STATE_SUSPENDED)
+					err = -ESTRPIPE;
+				break;
+			}
 			goto _again;
 			
 		}