On Mon, 2012-06-11 at 20:11 +0200, Lars-Peter Clausen wrote:
Currently the sound dmaengine pcm helper functions implement the pcm_pointer callback by trying to count the number of elapsed periods. This is done by advancing the stream position in the dmaengine callback by one period. Unfortunately there is no guarantee that the callback will be called for each elapsed period. It may be possible that under high system load it is only called once for multiple elapsed periods. This patch addresses the issue by implementing support for querying the current stream position directly from the dmaengine driver. Since not all dmaengine drivers support reporting the stream position yet the old period counting implementation is kept for now.
Furthermore the new mechanism allows to report the stream position with a sub-period granularity, given that the dmaengine driver supports this.
Acked-by: Vinod Koul vinod.koul@intel.com