At Fri, 25 Jan 2008 17:29:28 +0100, Hermann Lauer wrote: > > 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 ? The hwptr is the position of the current DMA. The data below that point must have been already processed. That's why hwptr returned in snd_pcm_period_elapsed() must be on the period boundary or above. OTOH, it doesn't matter much whether the data above hwptr has been processed or not, e.g. a sloppy pointer callback. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
