Re: Sound userspace drivers (fishing for insight)

[John Richard Moser <nigelenki@comcast.net>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1



Jaroslav Kysela wrote:
> On Tue, 7 Mar 2006, John Richard Moser wrote:
> 
>> In general, transporting sound data in and out of kernel space is a
>> horrid thought.  Consider the latencies, which all real-time audio
>> people will quickly get angry about.  Write sound; context switch; sound
>> in driver; context switch back.  This over and over?  Now we all know
>> better than that.
> 
> Nope. If you have a cache coherent architecture like x86, ALSA mmaps 
> directly the DMA buffer to application and even pointers to this buffer 
> are mmaped, thus there is no content switch when apps are doing r/w and 
> there is "zero data copy". The only contents switch is when apps call
> poll(), but you should do it, otherwise you'll eat all cpu time.
> 

Awesome.  Nice design  :)  I hath learned today and I woke up 10 minutes
ago.

>> into the kernel; with alsa it's written to a /proc interface, which
> 
> Using /proc? Where? I've not noticed it :-)

I thought that was what /proc/asound/card0/ was for?  :)
> 
> 						Jaroslav
> 
> -----
> Jaroslav Kysela <perex@suse.cz>
> Linux Kernel Sound Maintainer
> ALSA Project, SUSE Labs
> 

- --
All content of all messages exchanged herein are left in the
Public Domain, unless otherwise explicitly stated.

    Creative brains are a valuable, limited resource. They shouldn't be
    wasted on re-inventing the wheel when there are so many fascinating
    new problems waiting out there.
                                                 -- Eric Steven Raymond

    We will enslave their women, eat their children and rape their
    cattle!
                                     -- Evil alien overlord from Blasto
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.2.1 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
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=BSFO
-----END PGP SIGNATURE-----
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/