[Jack-Devel] alsa-jack plugin : wrong revents ?

Hello all,

I'm using code to interface with ALSA pcm devices that is
functionally identical to what alsa_driver_wait() in
Jack's alsa_driver.c is doing. More in particular the
parts

        if (need_playback) {
           if (snd_pcm_poll_descriptors_revents
                (driver->playback_handle, &driver->pfd[0],
                 driver->playback_nfds, &revents) < 0) {
                jack_error ("ALSA: playback revents failed");
                *status = -6;
                return 0;
            }

            if (revents & POLLERR) {
                xrun_detected = TRUE;
            }

            if (revents & POLLOUT) {
                need_playback = 0;

and

        if (need_capture) {
            if (snd_pcm_poll_descriptors_revents
                (driver->capture_handle, &driver->pfd[ci],
                 driver->capture_nfds, &revents) < 0) {
                jack_error ("ALSA: capture revents failed");
                *status = -6;
                return 0;
            }

            if (revents & POLLERR) {
                xrun_detected = TRUE;
            }

            if (revents & POLLIN) {
                need_capture = 0;


Now when the ALSA device is actually the alsa<->jack plugin used
for both playback and capture it seems that the expected POLLOUT
on the playback side revents never appears, instead I get a POLLIN
there as well. 

The same device works perfectly when tested for capture or playback
separately.

If I understand ALSA's snd_pcm_poll_descriptors_revents() correctly
it should 'normalize' the revents so that one always gets POLLOUT
for playback and POLLIN for capture. It seems that the plugin's
code is not doing this correctly when used in duplex mode.


Ciao,


-- 
FA

Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.

1325170384.14789_0.ltw:2,a <20111229145251.GA22822 at linuxaudio dot org>