On Thu, 25 Mar 2004, James Courtier-Dutton wrote:
> Jaroslav Kysela wrote:
> > On Wed, 24 Mar 2004, Paul Davis wrote:
> >
> >
> >>>open pcm, and get a handle.
> >>>
> >>>snd_pcm_poll_descriptors(handle, &pfd, err);
> >>>
> >>>Get a poll file scriptor in pfd.
> >>>
> >>>select(nfds, rfds, wfds, efds, tvp);
> >>>
> >>>Is it possible to use this call with alsa ?
> >>
> >>select is generally deprecated in linux (linus says so!). but you can
> >>use the same pfds in select as in poll (select is implemented in the
> >>kernel using the poll code). the problem is interpreting the results
> >>you get back (as noted recently for the dmix plugin).
> >
> >
> > Nope, the application must give results back to pfd array and call
> > snd_pcm_poll_descriptors_revents() function. In this way, everything
> > will work as expected.
> >
> > Jaroslav
> So which of the following is needed: -
>
> snd_pcm_poll_descriptors(handle, &pfd, err);
> select(nfds, rfds, wfds, efds, tvp);
> snd_pcm_poll_descriptors_revents() <- decode the results of the select.
This one. The *revents() function mangles the returned ->revents back to
the useful meaning for applications.
> or
> snd_pcm_poll_descriptors(handle, &pfd, err);
> snd_pcm_poll_descriptors_revents() <- rearrange the pfd so that select
> works as expected.
> select(nfds, rfds, wfds, efds, tvp);
That's wrong.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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