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SubjectRe: [OT] ALSA userspace API complexity
On Sun, 8 Jan 2006, Olivier Galibert wrote:

> On Sun, Jan 08, 2006 at 03:26:18AM +0100, Martin Drab wrote:
> > On Sun, 8 Jan 2006, Olivier Galibert wrote:
> >
> > > > And if the application doesn't support, who and where converts it?
> > > > With OSS API, it's a job of the kernel.
> > >
> > > Once again no. Nothing prevents the kernel to forward the data to
> > > userland daemons depending on a userspace-uploaded configuration.
> >
> > I think that the point was, that switching from userspace to kernelspace
> > then to userspace again and back to kernelspace in order to do something,
> > that could have been done directly in the userspace, and though could save
> > those two unnecessary switches, is an unnecessary overhead, which may not
> > necessarily be that insignificant if it's done so often (which for
> > streaming audio is the case).
> You all seem to forget that dmix is in userspace in a different task
> too.

Because it is really not. The mixing is done directly to the mmaped DMA

> > Why doing things complicated when there is no evident gain from it,
> > or is there?
> No evident gain? Wow. What about:
> - stopping crippling the OSS api

We're not doing that. We're just showing that OSS API and useability has
it's own problems, too.

> - having a real kernel api for which you can make different libraries
> depending on the need of the users
> - stop making a fundamentally unsecure shared library mandatory

ALSA kernel API is real and binary compatible. If someone require to
write an own library, we will document this API, of course, too.

> - opening the possibility of writing plugins to people without a PhD
> in lattice QCD.

Already done. We have official plugin SDK in alsa-lib to create user space
drivers. If you have some questions or bug-reports (missing docs etc),
please, fill a bug report.

Also, you can use very simple LADSPA plugin style, because alsa-lib can
use LADSPA plugins directly, too.


Jaroslav Kysela <>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs
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