Colin Walters walters at
Thu Jul 21 14:55:46 UTC 2005

On Thu, 2005-07-21 at 21:42 +1000, Russell Coker wrote:
>  Does ALSA require that a shared 
> memory segment be available to all programs that are accessing the sound 
> device? 

This is a consequence of switching to the ALSA "dmix" device by default,
which does transparent sound mixing in userspace via the shared memory.
This fixes the extremely user-visible bug of multiple applications not
being able to use the sound card at the same time.

Fundamentally though the IPC key doesn't have to be allocated by the
system; I wrote some code a while back that would have allocated it as
part of the X login, all in the normal user session so there was no
"system" part involved.  I'm still not sure why our ALSA maintainer
chose the ainit/PAM route given that you don't care about sound mixing
for any other means of logging in like ssh or virtual terminal.  Or at
least, I don't think we should care.

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