Re: PCM driver only plays tiny portion of clip

[Adrian McMenamin <adrian@mcmen.demon.co.uk>]

On Fri, 2006-03-03 at 08:27 +0100, Clemens Ladisch wrote:
> Adrian McMenamin wrote:
> > I think I have a good idea why my it is not working now - the DMA
> > routine which transfers sound samples from the main CPU memory to the
> > ring buffer of the hardware (which is effectively in a different memory
> > space) is in a kernel thread which, in essence, never gets rescheduled -
> > so the app thinks there is sound to be transferred but it never is -
> > hence it gets wedged.
> > 
> > To fix that I need to know what the alsa subsystem calls inside the
> > driver when it wants a DMA transfer to resume - I have to reschedule the
> > kernel thread there.
> 
> ALSA doesn't call the driver.  It assumes the hardware runs by itself.
> 
> If your hardware doesn't issue some interrupt regularly, you have to use
> a timer.
> 
It does have an interrupt - I am working on the idea of having the
kernel thread sleep and then wake up on the interrupt



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