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/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.
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
--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
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