USB-Audio: allow to configure period size for PCM split

The environment variable UCM_USB_PERIOD_TIME (microseconds / μs)
can define the period size for the PCM channel split over
the default value 10000μs.

BugLink: https://github.com/alsa-project/alsa-ucm-conf/pull/240
Fixes: https://github.com/alsa-project/alsa-ucm-conf/issues/238
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/ucm2/USB-Audio/USB-Audio.conf b/ucm2/USB-Audio/USB-Audio.conf
index 89482cbf5ab235ceda1abf6dcde958aad88af572..fdc29ecc7b117b2b70362114eccd01d8ab56e13f 100644 (file)
--- a/ucm2/USB-Audio/USB-Audio.conf
+++ b/ucm2/USB-Audio/USB-Audio.conf
@@ -4,6 +4,14 @@ Define.ProfileName ""
 Define.MixerRemap ""
 Define.SplitPCMPeriodTime 10000                # 10ms
 
+If.env1 {
+       Condition {
+               Type String
+               Empty "${env:UCM_USB_PERIOD_TIME}"
+       }
+       False.Define.SplitPCMPeriodTime "${env:UCM_USB_PERIOD_TIME}"
+}
+
 If.linked {
        Condition {
                Type RegexMatch