OSS API redirector

OSS API redirector

[Jaroslav Kysela]

Hi all,

	I would like to point all developers to the OSS API redirector 
which is in our alsa-oss package. It's universal piece of code which can 
redirect all OSS API calls (actually mixer & PCM API only) to any shared 
library.

Pros:
- no more LD_PRELOAD hacks
- any library can be used directly as endpoint
- when used more applications will work (also some which does not work
  with LD_PRELOAD hack)

Drawbacks:
- still no fopen/fclose/fwrite/fread solution
- applications must be a little bit modified

Todo:
- OSS sequencer API redirector (it shouldn't be too difficult)

	My original point is that we might persuade the binary only 
providers (mostly games vendors) to use this small piece of code, because
there are no impacts regarding the application useability and the 
maintaince overhead of this code is minimal.
	The second goal is to use this redirector for all OSS applications
in Linux distributions to make the routing over ALSA library more easy.

Usage of this redirector for OSS API emulation in ALSA:

export OSS_REDIRECTOR=libalsatoss.so

And define appropriate pcm.dsp0 and pcm.mixer0 in ~/.asoundrc.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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Re: OSS API redirector

[James Courtier-Dutton]

Jaroslav Kysela wrote:
> Hi all,
> 
> 	I would like to point all developers to the OSS API redirector 
> which is in our alsa-oss package. It's universal piece of code which can 
> redirect all OSS API calls (actually mixer & PCM API only) to any shared 
> library.
> 
> Pros:
> - no more LD_PRELOAD hacks
> - any library can be used directly as endpoint
> - when used more applications will work (also some which does not work
>   with LD_PRELOAD hack)
> 
> Drawbacks:
> - still no fopen/fclose/fwrite/fread solution
> - applications must be a little bit modified
> 
> -----
> Jaroslav Kysela <perex@suse.cz>
> Linux Kernel Sound Maintainer
> ALSA Project, SuSE Labs
> 

What is the conclusion regarding fopen/fclose/fwrite/fread.
Can it be done?

Cheers
James


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Re: OSS API redirector

[David Lloyd]

On Thu, 18 Mar 2004, James Courtier-Dutton wrote:

> What is the conclusion regarding fopen/fclose/fwrite/fread. Can it be
> done?

I thought that one rather pie-in-the-sky idea might be to use a kernel
module that made /dev/dsp, /dev/mixer, etc., and reflects back to a
userspace ALSA sound server via another device.  This way, it doesn't
matter how the device is opened.

Might be difficult to do though, especially when you get mmap and 
dma involved.

Just a thought, anyway.

- D


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Re: OSS API redirector

[James Courtier-Dutton]

David Lloyd wrote:
> On Thu, 18 Mar 2004, James Courtier-Dutton wrote:
> 
> 
>>What is the conclusion regarding fopen/fclose/fwrite/fread. Can it be
>>done?
> 
> 
> I thought that one rather pie-in-the-sky idea might be to use a kernel
> module that made /dev/dsp, /dev/mixer, etc., and reflects back to a
> userspace ALSA sound server via another device.  This way, it doesn't
> matter how the device is opened.
> 
> Might be difficult to do though, especially when you get mmap and 
> dma involved.
> 
> Just a thought, anyway.
> 
> - D
> 
> 
I thought of that, but with that you just get different problems.
E.g. dmix only works is all application wishing to play sound are run by 
the same user. You would probably need some daemon to run the /dev/dsp, 
and that user deamon would have to run under the same user as any native 
alsa app.

Cheers
James



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Re: OSS API redirector

[Jaroslav Kysela]

On Sun, 21 Mar 2004, James Courtier-Dutton wrote:

> I thought of that, but with that you just get different problems.
> E.g. dmix only works is all application wishing to play sound are run by 
> the same user. You would probably need some daemon to run the /dev/dsp, 

Nope. See the ipc_perm option (and we might enhance the permissions 
setup in future).

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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