From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Subject: Re: [PATCH 1/3] ALSA: compress_core: Update calc_avail
 to use cumulative values
Date: Tue, 09 Apr 2013 20:59:48 -0700
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To: Vinod Koul <vinod.koul@intel.com>
Cc: alsa-devel@alsa-project.org, broonie@opensource.wolfsonmicro.com, tiwai@suse.de, patches@opensource.wolfsonmicro.com, Pierre-Louis Bossart <pierre-louis.bossart@linux.jf.intel.com>, lgirdwood@gmail.com, Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
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> 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?
-Pierre