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-rw-r--r--Documentation/usb/gadget-testing.txt39
1 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/usb/gadget-testing.txt b/Documentation/usb/gadget-testing.txt
index 40d22d82cc5a..5ac9dc702c0e 100644
--- a/Documentation/usb/gadget-testing.txt
+++ b/Documentation/usb/gadget-testing.txt
@@ -17,6 +17,7 @@ provided by gadgets.
14. SERIAL function
15. SOURCESINK function
16. UAC1 function
+17. UAC2 function
1. ACM function
@@ -614,3 +615,41 @@ Testing the UAC1 function
device: run the gadget
host: aplay -l # should list our USB Audio Gadget
+
+17. UAC2 function
+=================
+
+The function is provided by usb_f_uac2.ko module.
+
+Function-specific configfs interface
+------------------------------------
+
+The function name to use when creating the function directory is "uac2".
+The uac2 function provides these attributes in its function directory:
+
+ chmask - capture channel mask
+ c_srate - capture sampling rate
+ c_ssize - capture sample size (bytes)
+ p_chmask - playback channel mask
+ p_srate - playback sampling rate
+ p_ssize - playback sample size (bytes)
+
+The attributes have sane default values.
+
+Testing the UAC2 function
+-------------------------
+
+device: run the gadget
+host: aplay -l # should list our USB Audio Gadget
+
+This function does not require real hardware support, it just
+sends a stream of audio data to/from the host. In order to
+actually hear something at the device side, a command similar
+to this must be used at the device side:
+
+$ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &
+
+e.g.:
+
+$ arecord -f dat -t wav -D hw:CARD=UAC2Gadget,DEV=0 | \
+aplay -D default:CARD=OdroidU3