ALSA: compress: document the compress gapless audio state machine

Also documented the galpess transitions. Please note that these are not
really stream states, but show how the stream steps in gapless mode

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20200629134737.105993-3-vkoul@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst
index ad89af9b31c98eda168ee96ae963a2a617b8ccb4..935f325dbc773a8b63edaf84f86e05315a1e315d 100644 (file)
--- a/Documentation/sound/designs/compress-offload.rst
+++ b/Documentation/sound/designs/compress-offload.rst
@@ -250,6 +250,38 @@ Sequence flow for gapless would be:
 
 (note: order for partial_drain and write for next track can be reversed as well)
 
+Gapless Playback SM
+===================
+
+For Gapless, we move from running state to partial drain and back, along
+with setting of meta_data and signalling for next track ::
+
+
+                                        +----------+
+                compr_drain_notify()    |          |
+              +------------------------>|  RUNNING |
+              |                         |          |
+              |                         +----------+
+              |                              |
+              |                              |
+              |                              | compr_next_track()
+              |                              |
+              |                              V
+              |                         +----------+
+              |                         |          |
+              |                         |NEXT_TRACK|
+              |                         |          |
+              |                         +----------+
+              |                              |
+              |                              |
+              |                              | compr_partial_drain()
+              |                              |
+              |                              V
+              |                         +----------+
+              |                         |          |
+              +------------------------ | PARTIAL_ |
+                                        |  DRAIN   |
+                                        +----------+
 
 Not supported
 =============