On 2019-11-05 20:36, 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.
If you have another ideas to address those issues, please, let me
know.
BTW, Mark: The SOF UCM configs relies on the driver name changes,
so it might be worth to send "ASoC: intel - fix the card names" patch to
5.4 to make things stable more quickly:
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git/commit/?h=for-5.5&id=d745cc1ab65945b2d17ec9c5652f38299c054649
Thanks,
Jaroslav
Thanks for your work, Jaroslav.
However, I have some concerns here. First, could you elaborate on "we
require for the SOF kernel driver"?
The substitutions and multi-instance support is probably warmly welcomed
by many, but "If" blocks are what worries me. Especially the nested
"Ifs". As Takashi pointed already out, UCM - which is currently is
viewed as a simple configuration syntax - is becoming a language on its
own. If we are to keep extending UCM on and on, we might as well switch
to JSON/ XML/ YAML entirely instead of developing our own thingy.
"If" block could just be what's needed to open new pandora box, allowing
for very complex and no longer easy-to-read config files. In general, if
one is to enlist an "If", why not define two UCMs instead?
Moreover, I see you mentioning the card-name dependency. This sounds
rather invasive. Separation of different config-versions would be required.
Czarek
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