Re: [RFC PATCH (alsa-lib)] pcm: Modify check condition in snd_pcm_sw_params_set_avail_min

[Mark Brown <broonie@kernel.org>]

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On Thu, Sep 03, 2015 at 03:45:46PM +0800, Koro Chen wrote:
> On Thu, 2015-09-03 at 09:08 +0200, Takashi Iwai wrote:

> > How this happens?  The period size is the size where irq (or wakeup)
> > wakes up for read/write.  Why the driver wakes up even if there is no
> > enough data?

> Yes it is odd to what we would normally expect. Due to our HW design,
> when irq comes, audio HW actually has collected a full period of data,
> but there is a buffer between the audio HW and memory, so at that moment
> some samples are still in the buffer, not on the memory. Add a small
> delay between triggering capture HW and enabling IRQ can also fix this,
> although I think changing the avail_min should be better. 

This does sound like something that should be handled in the kernel -
one thing we should be doing is providing a uniform interface to
userspace.

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