On Sat, 26 Jul 2003, Prince John wrote:
> Hi,
> I have a few queries on buffer pointer updation during
> playback operation with DMA transfer. I have gone
> through the documents, but some are not very clear.
> I have 64KB DMA buffer and 16KB period size. I'm using
> runtime->dma_addr as the DMA source (physical
> address). Is this right? This address never getting
> changed during run time. I get interrupt in 16K
> periods. Should I add the 16KB offset to the
> runtime->dma_addr for next block of data transmission?
No, don't do this. Simply return the right buffer position via
the pointer callback.
> And should it be wrapped around to runtime->dma_addr
> after 64KB transfer? I tried some of these, but the
> sound gererated is not proper.
> The runtime->status->hw_ptr also seen as a constant
> during run time. The pointer call backs are returned
> with the number of frames transmitted (offset from the
> buffer start address).
>
> Could you please give your suggestions ?
I guess that you forgot to call snd_pcm_period_elapsed()
in your interrupt handler to notify the midlevel code that
the transfer of a period is done.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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