[PATCH v4 3/3] ALSA: Documentation about HDA DP MST pin init and connection

[libin.yang@intel.com]

From: Libin Yang <libin.yang@intel.com>

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

Signed-off-by: Libin Yang <libin.yang@intel.com>
---
 Documentation/sound/hd-audio/dp-mst.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/sound/hd-audio/dp-mst.rst b/Documentation/sound/hd-audio/dp-mst.rst
index 58b7243..1617459 100644
--- 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
 ====
-- 
2.7.4