Clemens Ladisch wrote: > Florian Winter wrote: > >> Suppose, an ALSA playback device is opened in blocking mode, and one >> thread calls snd_pcm_writei. If the snd_pcm_writei call blocks, because >> the internal buffer of the ALSA device is full, is there a way by which >> another thread can interrupt the call, so it returns immediately without >> writing any data to the device? >> > > No. As far as the user-space library is concerned, ALSA is not thread > safe. > > You have to use non-blocking mode and poll() so that you can send a > message through a file descriptor (e.g. pipe or eventfd). > Thank you. This is also the only option I see. This leads to some more questions: I can't derive from the documentation when exactly my poll() call will wake up. Is there a way to tell ALSA something like: "I want to write at least N frames to the device without blocking. Please don't wake up my poll() call until I can do this" (assuming that N is a meaningful value, i.e. less than the total buffer size)? If I can not control this parameter N, is there at least a way to query it from ALSA? Will the ALSA device always become writeable when N bytes can be written, or is the ALSA implementation (driver implementation) free to decide when and when not to block? Best regards, Florian ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
