Re: Scatter Gather

[Takashi Iwai <tiwai@suse.de>]

At Tue, 02 Mar 2004 11:16:33 +0100 (CET),
Giuliano Pochini wrote:
> 
> 
> On 02-Mar-2004 Manuel Jander wrote:
> 
> >> Yes.  Every driver using SG must do this.  Look into bt87x.c or
> >> via82xx.c for examples.
> > 
> > Well, i guess in that case the period size loses any relevance in
> > terms of efficiency.
> 
> Efficiency about what ?  If the hardware can be programmed to use
> any period size, then the application is free to choose the size
> it prefers. It's not a bad thing.  NB: the interrupt should be
> generated at the end of the period, not at the end of each block,
> eg. when it crosses the page boundary.

well, it's ok to generate irqs at each page boundary, too, as long as
the driver processes it properly, i.e. calling
snd_pcm_period_elapsed() only at the irq of the end of period.
of course, less irqs are better from the performance viewpoint.


Takashi


-------------------------------------------------------
SF.Net is sponsored by: Speed Start Your Linux Apps Now.
Build and deploy apps & Web services for Linux with
a free DVD software kit from IBM. Click Now!
http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click