[alsa-devel] es1938 - patch trying to improve capture hw pointer reads

Hermann Lauer Hermann.Lauer at iwr.uni-heidelberg.de
Fri Jan 25 17:29:28 CET 2008

On Fri, Jan 25, 2008 at 05:19:52PM +0100, Takashi Iwai wrote:

> > If I interpreted my tests output correctly, the last byte of a period
> > is written by the DMA engine after the interrupt occurs. So the
> > hw pointer probably has to be decremented by one and is then
> > pointing to the last frame (Or even that before: Has the hw pointer to point
> > at the frame which is written at the moment or the one which is
> > guaranteed to be written completely by the hardware ?)
> This sounds a bit odd.  Isn't it rather the setup of the hardware
> parameter wrong?  I mean, the count calculation in *_prepare() can be
> the size - 1?  

At least according to the datasheet the size calculation is correct.
Could you please tell me where the hw pointer exactly should point to ?


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