Re: [alsa-devel] UCM extensions

[Takashi Iwai <tiwai@suse.de>]

On Tue, 05 Nov 2019 20:36:28 +0100,
Jaroslav Kysela wrote:
> 
> Hi all,
> 
> 	I make some internal ucm code cleanups in alsa-lib and added
> three major extensions to allow more complex configurations which we
> require for the SOF kernel driver.
> 
> 	The first thing is the added substitution for the value strings:
> 
> https://github.com/alsa-project/alsa-lib/commit/f1e637b285e8e04e6761248a070f58f3a8fde6fc
> 
> 	The second thing is the If block:
> 
> https://github.com/alsa-project/alsa-lib/commit/985715ce8148dc7ef62c8e3d8ce5a0c2ac51f8df
> 
> 	The third thing is the card / hardware like specifier passed
> as the ucm name to snd_use_case_mgr_open() to support multiple card
> instances:
> 
> https://github.com/alsa-project/alsa-lib/commit/60164fc5886cdc6ca55eeed0c2e3f751a7d2b2c0
> 
> 	All those patches (with other cleanups) are in the ucm2 branch
> on github for comments:
> 
> https://github.com/alsa-project/alsa-lib/commits/ucm2
> 
> 	The proposed SOF UCM config diff is here:
> 
> https://github.com/alsa-project/alsa-ucm-conf/commit/723b6da881721488229154e923ed36413955a051
> https://github.com/alsa-project/alsa-ucm-conf/commits/ucm2
> 
> 	I added everything to keep the interface backward compatible,
> so the current applications should not observe any different
> behavior. The applications like pulseaudio should use the
> 'hw:CARD_INDEX' specifier for the open call in the future and
> snd_use_case_parse_ctl_elem_id() helper for the element control names.

The only concern with these extensions so far is the compatibility.
Imagine that people run the new profile on the old parser, it'd break
easily.

I think other scripts often installing on the versioned directory if
incompatibilities are seen.  Can we do that for UCM as well?

Or course, once after UCM parser is changed to be future-ready and
allow some syntax for possible future extensions, we can keep that
version directory in future, too.


thanks,

Takashi
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