>> >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).
>
>select and pselect do allow for a more accurate timeout specification.
>Why is select deprecated?
well, one reason might be gleaned from the man page for select_tut:
[ ... ]
mode at all (see ioctl(2)). It is easy to introduce subtle errors that
will remove the advantage of using select, hence I will present a list
of essentials to watch for when using the select call.
1. You should always try use select without a timeout. Your program
should have nothing to do if there is no data available. Code
that depends on timeouts is not usually portable and difficult
to debug.
of course, for main event loops in things like glib, this can't ever
really be true, but it is a rather salient point for most callers of
select().
i think the main reason for its "deprecation" (which is very mild,
given that its an official POSIX call) is that its semantics are not
quite as clear as poll(2). its even possible that i've missed a
retraction from linus about this.
--p
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