[alsa-devel] [PATCH v2 1/6] Documentation: soundwire: Add documentation for Multi link

[Shreyas NC]

From: Sanyog Kale <sanyog.r.kale at intel.com>

Add example and documentation to describe Multi Link streams

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
Signed-off-by: Sanyog Kale <sanyog.r.kale at intel.com>
Signed-off-by: Vinod Koul <vkoul at kernel.org>
Signed-off-by: Shreyas NC <shreyas.nc at intel.com>
---
 Documentation/driver-api/soundwire/stream.rst | 29 ++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/Documentation/driver-api/soundwire/stream.rst b/Documentation/driver-api/soundwire/stream.rst
index 29121aa..11623aab 100644
--- a/Documentation/driver-api/soundwire/stream.rst
+++ b/Documentation/driver-api/soundwire/stream.rst
@@ -75,7 +75,6 @@ Slaves are using single port. ::
 	                                                   |     (Data)    |
 	                                                   +---------------+
 
-
 Example 4: Stereo Stream with L and R channel is rendered by two different
 Ports of the Master and is received by only single Port of the Slave
 interface. ::
@@ -101,6 +100,34 @@ interface. ::
 	+--------------------+                             |                |
 							   +----------------+
 
+Example 5: Stereo Stream with L and R channel is rendered by 2 Masters, each
+rendering one channel, and is received by two different Slaves, each
+receiving one channel. Both Masters and both Slaves are using single port. ::
+
+	+---------------+                    Clock Signal  +---------------+
+	|    Master     +----------------------------------+     Slave     |
+	|   Interface   |                                  |   Interface   |
+	|       1       |                                  |       1       |
+	|               |                     Data Signal  |               |
+	|       L       +----------------------------------+       L       |
+	|     (Data)    |     Data Direction               |     (Data)    |
+	+---------------+  +----------------------->       +---------------+
+
+	+---------------+                    Clock Signal  +---------------+
+	|    Master     +----------------------------------+     Slave     |
+	|   Interface   |                                  |   Interface   |
+	|       2       |                                  |       2       |
+	|               |                     Data Signal  |               |
+	|       R       +----------------------------------+       R       |
+	|     (Data)    |     Data Direction               |     (Data)    |
+	+---------------+  +----------------------->       +---------------+
+
+Note: In multi-link cases like above, to lock, one would acquire a global
+lock and then go on locking bus instances. But, in this case the caller
+framework(ASoC DPCM) guarantees that stream operations on a card are
+always serialized. So, there is no race condition and hence no need for
+global lock.
+
 SoundWire Stream Management flow
 ================================
 
-- 
2.7.4