Anders Torger wrote: > >On Wednesday 11 September 2002 20.48, you wrote: >> On Wed, 11 Sep 2002, Anders Torger wrote: >> > I use a RME9652 hammerfall with two periods (the hardware is that >> > way). >> > >> > I watch a file descriptor associated to the output with select(), >> > when it gets ready for writing, I write data to the pcm with >> > snd_pcm_writen(). In the beginning, the state of the pcm is >> > PREPARED. >> > >> > What I would expect then, is that the file descriptor is ready for >> > writing until the two periods has been filled with data, and then >> > select will block (output buffers full, sound card not running). >> > But instead, when the two periods is filled with data, select() >> > still returns and says that the file descriptor is ready for >> > writing, but when calling snd_pcm_writen(), it returns -EPIPE. The >> > pcm state is still PREPARED. >> > >> > What is wrong? Is it me (probably), or is it alsa? >> >> You should also check for POLLERR. I'm not sure, that it's necessary >> to return POLLOUT together with POLLERR in that case. Anyway, >> application should check for POLLERR at first and then write data. > >I'm sorry, I don't understand, what would be the error in the above >case? I just want to watch the file descriptor for writing, and expect >that it will be triggered when there is available space in the output >buffer to write to, or, if there is an error, for example broken pipe. >But how could it be broken pipe if the pcm is in state PREPARED? It has >never been put into RUNNING. > >The problem here is that the output buffer is full, the pcm is not >RUNNING, but the file descriptor gets triggered anyway. When can that >happen?
we had a hauntingly similar discussion about this a few months ago, maybe a year. iirc everybody considered the pcm behaviour broken, except for the alsa coders. seeing that you come to the same conclusion makes me again vote for changing this behaviour to 'poll/select blocks until running'. tim ------------------------------------------------------- In remembrance www.osdn.com/911/ _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
