From mboxrd@z Thu Jan  1 00:00:00 1970
From: Clemens Ladisch <clemens@ladisch.de>
Subject: Re: HDA driver without interrupt
Date: Thu, 03 May 2012 10:37:52 +0200
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To: Fanchao Liu <liufc10@gmail.com>
Cc: alsa-devel@alsa-project.org
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Fanchao Liu wrote:
> It can transfer data via DMA,the problem is I don't know when to
> update hw_ptr and other pointers without interrupt.

Does the hardware have some other means to at least read the current
position?

> I set a timer and call snd_pcm_period_elapsed() every 50ms but get
> underrun error.

With a call to snd_pcm_period_elapsed(), the driver guarantees that the
current position is at or after the next period boundary.


Regards,
Clemens