[alsa-devel] soc-dsp questions

pl bossart bossart.nospam at gmail.com
Tue Apr 26 00:01:12 CEST 2011

To prepare next week's ALSA-Asoc meeting, I reviewed Liam's
dsp-upstream code, and I am a bit unclear on the 'no_host_mode'
supported by some DAIs. Apparently these are regular ALSA PCM
substreams, except that there are no data exchanges to/from the host.
- If these substreams are known, an application can in theory
open/close them. How would it know that no data is to be written/read?
I would think additional changes are required in alsa-lib?
- is this really important that such PCM devices be known in
userspace? Or are they declared only so that ALSA controls are enabled
for these streams?
- along the same lines, how useful is the .pointer routine for such
devices? Since no data will be provided by the host, is this really
needed? I see it's only meaningful for the low-power playback mode,
but I am unsure if the information provided would actually be used by
- what is the meaning of the SND_SOC_DAI_LINK_OPT_HOST definition? It
doesn't seem to be updated depending on which back-end is used, so it
this really needed?

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