pcm sound driver for SBus Ultra1/Ultra2

Pyun YongHyeon yongari at kt-is.co.kr
Thu Jul 1 21:10:21 PDT 2004

On Thu, Jul 01, 2004 at 08:25:40PM -0600, Scott Long wrote:
 > Once again, you've done another impressive job =-)  The biggest question
 > that I have is why you chose to base the work on the mss driver and not
 > the cs428x driver.  I looked at this briefly a few weeks ago and
 > decided (after also looking at NetBSD) that it really only needed to be
 > abstracted so it could take both a PCI and an SBUS front-end.  The only
 > thing that held me back was the lack of busdma support.

Well, I didn't check cs4281 datasheet. After reading the source I
thought it would be different enough to require new driver.(AC97,
DMA, sampling frequency etc.)
 One of major problems for SBus cs4231 driver was lack of APC DMA
doucumentation and no existing SBus pcm driver for reference. So
I borrowed the APC DMA code from OpenBSD, and adopted mixer routine
from mss with small modifications.(mss driver supports the same chip

If mss driver was designed well with BUS DMA in mind it would
be possible to take SBus frontend. But I still dout it due to
dramatic differences between DMA interface and interrupt
handling. In addition, existing driver may need modification
which is beyond scope of my ability.

 > Since this requires stubs into sndbuf_dma.c it might not be totally
 > appropriate as it is, but I'd like to also review it further over the
 > next few days and get back to you.  Thanks!
Yes, this was not good solution.  I'm not sound guy at all, and
have little knowledge of pcm(4) internals. The method I took was
the fastest path to realize the driver.

Thanks a lot.

 > Scott

Pyun YongHyeon
Pyun YongHyeon <http://www.kr.freebsd.org/~yongari>

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