[alsa-devel] Maximum buffer size on HDA

[Takashi Iwai]

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.


Takashi