ALSA in a 2.6 world

[Fernando Pablo Lopez-Lezcano]

On Thu, 2004-04-15 at 23:28, Florin Andrei wrote:
> On Thu, 2004-04-15 at 23:22, Axel Thimm wrote:
> > On Thu, Apr 15, 2004 at 07:29:38PM -0700, Florin Andrei wrote:
> > > Long story made short, is there any mechanism provided by Fedora Core 2
> > > to allow users to painlessly upgrade to newer ALSA versions without
> > > having to ditch the kernel bundled with the distribution?
> > 
> > For FC1 and higher modutils have even a special folder for
> > external kernel module upgrades under /lib/modules/`uname -r`/updates
> > for exactly that purpose.
> 
> Excellent! That answers my question. Thank you.

There are a couple more issues that pertain to doing "professional"
audio under 2.6.x that are not addressed by the current Fedora Core
kernel builds, AFAIK (I very briefly tried 2.6 using Arjanv's source
packages as a base, last build was based on kernel 1.286 - maybe the
following is different in the "official" kernel). 

If you are concerned about latency (ie: using very small audio buffers)
then the stock configuration of the 2.6.x kernel has the preemptible
kernel option turned off. In my tests latency is worse than with it
on[1]. 

If you want to use the Jack low latency audio server (Jack Audio
Connection Kit) with realtime privileges (SCHED_FIFO) then the obvious
alternative is to build and load the LSM kernel module[2]. Regretfully
that would need CONFIG_SECURITY_CAPABILITIES to be a module instead of
being built into the kernel, as in the last build I tried (otherwise you
can't build the LSM module). 

-- Fernando

[1] plus the drm kernel modules for radeon/r128/mga have 12mSec+ latency
hits and an old patch I used to use is broken...

[2] http://www.joq.us/realtime/