Date: Thu, 24 Jul 1997 16:57:32 -0700 From: Amancio Hasty <hasty@rah.star-gate.com> To: Brian Campbell <brianc@pobox.com> Cc: freebsd-multimedia@FreeBSD.ORG Subject: Re: sb16 request Message-ID: <199707242357.QAA16379@rah.star-gate.com> In-Reply-To: Your message of "Thu, 24 Jul 1997 18:59:07 EDT." <19970724185907.39493@pobox.com>
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Currently on 3.5 based sound drivers , only one descriptor is used
for read and write and I want to keep it that way given that most
decent api's already support that mechanism --- sun and sgi .
There is an ioctl to specify the number of bits perhaps it will be
just as easy to extend it to support both read and write channels
sample size . If I am not mistaken the current mechanism only uses
a byte to specify 8 or 16 so a simple extension could be to specify
the read channel bit size on the second half of the word. If not
then the default should be that it applies to both read and write
if the card supports full duplex operation;otherwise, it should
only apply to the the read or write channel.
Cheers,
Amancio
>From The Desk Of Brian Campbell :
> On Thu, Jul 24, 1997 at 03:43:15PM +0200, Luigi Rizzo wrote:
> > I am looking at the sb16 operation in full duplex using dual dma (one
> > 8-bit, the other 16-bit):
> >
> > Which one fo the following approaches people prefers:
> >
> > 1. always use 16-bit for play, 8-bit for record;
> > 2. always use 16-bit for record, 8-bit for play;
> > 3. allocate the 16-bit channel to the first type of request (read or
> > write) and use the 8-bit channel for the other one.
> >
> > or
> >
> > 4. define a new ioctl to chose which channel gets the 16-bit dma and
> > which one gets the 8-bit dma, with some default camong those
> > described before.
>
> There's already a mechanism to specify the number of bits used for
> playback/record and its format. The default on open() is 8-bit (I
> think) and I suppose it should remain that way. If either playback
> or record wants 16-bit then the appropriate ioctl should be used.
> If the other channel requested it first, the second will fail.
> I'm assuming two descriptors are in use, one RDONLY the other
> WRONLY.
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