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SubjectRe: ANNOUNCE: big change in PCM kernel API
Alan Cox wrote:
>
> > The only drawback is that the maximum number of pcm devices for card is
> > decreased to 8 from 16, but this will change when linux kernel will use
> > a wider kdev_t.
> >
> > Obviously the OSS emulation behaviour is intact.
>
> The OSS API appears to be making a subtle change for 2.4, not one I planned
> but one that several groups arrived at and which I can't find an application
> that breaks from.
>
> On the new trident driver and on the SB Live! driver opening /dev/dsp gets
> you a new free channel if there are any free channels on the card.
>
> Both drivers get the locking wrong right now (hint - need to drop the inode
> lock as they share the inode and one sleeping on a write locks out the other)
> but the API change seems sane and I think we should tweak other cards with
> many channels to do the same (eg the ESS Maestro)
>
> Views from the ALSA side ?
>
> Alan

ALSA has already the same behaviour (also for OSS emulation) and the
inode lock is dropped on write (to tell you the truth I'd have preferred
that sys_write transfer the inode->i_sem handling entirely to
f_op->write, but probably the efficiency impact of the double down/up is
small)

I'm not sure to understand the second part (and one sleeping on a write
locks out the other), can you rephrase that?

--
Abramo Bagnara mailto:abramo@alsa-project.org

Opera Unica
Via Emilia Interna, 140 Phone: +39.0546.656023
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ALSA project is http://www.alsa-project.org
sponsored by SuSE Linux http://www.suse.com

It sounds good!

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