[alsa-devel] Maximum buffer size on HDA

[Jaroslav Kysela]

On Mon, 16 Jun 2008, Takashi Iwai wrote:

> At Fri, 13 Jun 2008 21:13:03 +0200,
> Lennart Poettering wrote:
> > 
> > Heya,
> > 
> > the HDA driver allows a playback buffer size of something like 64K
> > onyl. Is this a driver limitation or a limitation of the hardware?
> > Skimming through the docs I cannot see anything like this, and I got
> > the idea that the audio buffer is maintained in system memory, not
> > sound card memory, so why this limit?
> 
> This comes from the buffer pre-allocator.
> Run the below:
> 
> 	# echo 1024 > /proc/asound/card0/pcm0p/sub0/prealloc
> 
> then you can use now 1MB buffer.  snd-hda-intel has max
> pre-allocation buffer size 1MB, and this is the hard-coded limit.
> 
> It's rather a silly constraint, and I think it'd be better cut off.
> OTOH, this makes the system safer (e.g. avoiding page allocations for
> too large buffers), and there is a proper workaround, too.
> So, I'm open about this change, so far.

Which workaround you're talking about?

					Jaroslav

-----
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.