Takashi Sakamoto wrote: > On May 4 2016 22:59, Charles Keepax wrote: >> if (PCM_RUNTIME_CHECK(substream)) >> - return -ENXIO; >> + return POLLIN | POLLRDNORM | POLLERR; > > [...] > On the other hand, I think POLLOUT, POLLIN, POLLWRNORM and POLLRDNORM > should not be included in the value. PCM_RUNTIME_CHECK() ensures PCM > substream or PCM runtime is NULL. This means that subsequent I/O > operations are failed, at least for handling PCM frames. > > I think it better to return 'POLLERR | POLLHUP'. To expand on this: POLLIN/POLLOUT imply that it is possible to read/ write data without blocking. Sockets and pipes combine POLLHUP with POLLIN because the read() (or recv()) returns 0 bytes without blocking to indicate the end of the stream. But in this situation, snd_pcm_read*/write* will always fail, so it is, strictly speaking, indeed not appropriate to set POLLIN/OUT. On the other hand, PCM devices do include the POLLIN/OUT bits when they are in a wrong state. (This is probably to catch programs that do not check the error bits; with POLLIN/OUT set, these programs will try to read/write, and will then get the error code.) So for consistency, the bits should be included. (Or the other error case fixed to remove these bits.) Regards, Clemens _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
