[alsa-devel] hw_params function and OSS emulation

Takashi Iwai tiwai at suse.de
Wed Aug 22 17:57:13 CEST 2007

At Wed, 22 Aug 2007 10:48:44 -0500,
Timur Tabi wrote:
> Takashi Iwai wrote:
> > The driver should deny a too large size if it's unrealistic.
> > But 1MB is realistic for many systems.  So, the number depends on the
> > system.
> Are there any popular applications that really want a DMA buffer
> larger than 64KB? 

It's something like an urban legend: the bigger, the better.
A big buffer seems preferred for applications that require the robust
operation.  Such a requirement makes a little bit sense although
multi-threading and adjusting the RT-priority would give you far
better result.

> On a side note, I notice that ALSA has some scatter-gather support.  If an 
> application uses S/G, I presume the concept of a DMA buffer size doesn't even 
> apply?

The SG-buffer isn't for applications but for drivers.  From the
application viewpoint, the buffer looks linear.


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