[alsa-devel] [PATCH 1/3] ALSA: compress_core: Update calc_avail to use cumulative values

Pierre-Louis Bossart pierre-louis.bossart at linux.intel.com
Wed Apr 10 05:59:48 CEST 2013

> we can normally use offsets to work and do all the calculation in the core. But
> this check fails when app_ptr = hw_ptr. Here we dont know if the buffer is full
> or empty :) So we need to look at cummulative values for those checks, hence the
> core maintains both of these and IIRC looks at cummulative values when
> calucating avail only when we hit the above condition or probably in case when
> we wrap over the ring buffer.
> In both memory mapped and non mapped these cases are true so I dont see why this
> caluclation is specfic for memory maped DSPs. There is nothing in this case
> which relies. We only use the values reported by DSP and internal counters...

the question was whether we need these offsets at all. Can't we just use 
cumulative values everywhere?

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