ALSA: Documentation about HDA DP MST pin init and connection

Add the documentation about HD-audio DP MST:
1. pin initialization
2. device entry connection list

Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Libin Yang <libin.yang@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1484208294-8637-4-git-send-email-libin.yang@intel.com

diff --git a/Documentation/sound/hd-audio/dp-mst.rst b/Documentation/sound/hd-audio/dp-mst.rst
index 58b72437e6c3e27573ab7d640ff8310b2250889d..1617459e332fdd92af570e0bd1092262e0832583 100644 (file)
--- a/Documentation/sound/hd-audio/dp-mst.rst
+++ b/Documentation/sound/hd-audio/dp-mst.rst
@@ -19,6 +19,23 @@ PCM
 ===
 To be added
 
+Pin Initialization
+==================
+Each pin may have several device entries (virtual pins). On Intel platform,
+the device entries number is dynamically changed. If DP MST hub is connected,
+it is in DP MST mode, and the device entries number is 3. Otherwise, the
+device entries number is 1.
+
+To simplify the implementation, all the device entries will be initialized
+when bootup no matter whether it is in DP MST mode or not.
+
+Connection list
+===============
+DP MST reuses connection list code. The code can be reused because
+device entries on the same pin have the same connection list.
+
+This means DP MST gets the device entry connection list without the
+device entry setting.
 
 Jack
 ====