On Mon, 2011-04-25 at 17:01 -0500, pl bossart wrote:
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.
Ah, this part is WIP and will not be part of the initial submission. We are currently using this for audio between the MODEM and ABE that does not pass through the CPU.
- 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?
The intention is that userspace apps would know there is no data, but this is probably better discussed at conference. It may also require an alsa-lib update too.
- 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 anyone?
I think in most cases pointer() would not be required here.
- 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?
Again, this part is WIP and was used to signal that the DAI could be optionally be used in no host mode.
Liam
Thanks -Pierre _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel