Dne 07. 11. 19 v 7:48 Takashi Iwai napsal(a):
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/f1e637b285e8e04e6761248a070f...
The second thing is the If block:
https://github.com/alsa-project/alsa-lib/commit/985715ce8148dc7ef62c8e3d8ce5...
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/60164fc5886cdc6ca55eeed0c2e3...
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/723b6da881721488229154e... 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.
While we are going to separate UCM files from alsa-lib to alsa-ucm-conf we can define the new syntax change until the first version is released (I can put a notice to README).
Speaking for Fedora, we have dependancy 'alsa-lib package version' must be equal to 'alsa-ucm package version'. If users will do any changes on their own, they should know what they are doing.
Anyway, we should learn from this and I would propose to add add something like 'Syntax 2' to the main configuration file now. The new functions should be activated only according the version.
Unfortunately, the current parser will just show an error message like:
ALSA lib parser.c:1337:(parse_master_file) uknown master file field Syntax ALSA lib parser.c:1337:(parse_master_file) uknown master file field If
But at least, users should be notified that there is a configuration mismatch.
Another possibility is to change the suffix for the master configuration file to accept the "Syntax" check for the another future update. But honestly, I don't like ".conf2" and ".v2.conf" looks not so nice, too.
Jaroslav