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To: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
cc: dec@phoenix.its.rpi.edu, hackers@FreeBSD.ORG, multimedia@FreeBSD.ORG
Subject: Re: IRQ problem (was Re: IRQ timing) 
In-reply-to: Your message of "Sun, 31 Aug 1997 06:24:16 +0200."
             <199708310424.GAA03702@labinfo.iet.unipi.it> 
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Date: Sat, 30 Aug 1997 22:46:00 -0700
From: Amancio Hasty <hasty@rah.star-gate.com>
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In guspnpxxx or linux sound driver 3.5 adaption for FreeBSD uses 64kb for
the dma buffer, the default size for dma requests is a 1/2 second.

If the user specifies a block size the dma buffer gets split in N blocks
of the specified user block size and the dma buffer remains 64k.

	Amancio

>From The Desk Of Luigi Rizzo :
> > > > o buffer size used in in the application
> > > 
> > > i guess you also need the blocksize -- the size of each DMA transfers
> > > -- and not only the total amount of buffers.
> > 
> > True but bear in mind that the system has plenty of memory:
> ...
> > I would hope that the OSS driver has the heuristics to allocate 
> > sufficient memory for the buffers.
> 
> I think the default is 64K (seen in some include file). What I am not
> sure about is if the blocksize for DMA transfer is determined
> adaptively if the user does not call some SETFRAGMENT or SUBDIVIDE
> ioctl. In my code I wrote some code to use 0.25s of audio for each DMA
> transfer unless the user specifies elsewhere (using the above calls or
> the new one that I introduced, AIOSSIZE).
> 
> What about guspnpXX ?
> 
> 	Luigi