3 files changed, 46 insertions, 0 deletions
diff --git a/Documentation/DocBook/v4l/media-ioc-enum-links.xml b/Documentation/DocBook/v4l/media-ioc-enum-links.xml
index 6da884159cab..d2fc73ef8d56 100644
--- a/Documentation/DocBook/v4l/media-ioc-enum-links.xml
+++ b/Documentation/DocBook/v4l/media-ioc-enum-links.xml
@@ -179,6 +179,11 @@
 	    <entry>The link enabled state can't be modified at runtime. An
 	    immutable link is always enabled.</entry>
 	  </row>
+	  <row>
+	    <entry><constant>MEDIA_LNK_FL_DYNAMIC</constant></entry>
+	    <entry>The link enabled state can be modified during streaming. This
+	    flag is set by drivers and is read-only for applications.</entry>
+	  </row>
 	</tbody>
       </tgroup>
     </table>
diff --git a/Documentation/DocBook/v4l/media-ioc-setup-link.xml b/Documentation/DocBook/v4l/media-ioc-setup-link.xml
index 09ab3d2b3a52..2331e76ded17 100644
--- a/Documentation/DocBook/v4l/media-ioc-setup-link.xml
+++ b/Documentation/DocBook/v4l/media-ioc-setup-link.xml
@@ -60,6 +60,9 @@
     <para>Link configuration has no side effect on other links. If an enabled
     link at the sink pad prevents the link from being enabled, the driver
     returns with an &EBUSY;.</para>
+    <para>Only links marked with the <constant>DYNAMIC</constant> link flag can
+    be enabled/disabled while streaming media data. Attempting to enable or
+    disable a streaming non-dynamic link will return an &EBUSY;.</para>
     <para>If the specified link can't be found the driver returns with an
     &EINVAL;.</para>
   </refsect1>
diff --git a/Documentation/media-framework.txt b/Documentation/media-framework.txt
index 4809221c0ff9..fd48add02cb0 100644
--- a/Documentation/media-framework.txt
+++ b/Documentation/media-framework.txt
@@ -313,3 +313,41 @@ Link configuration must not have any side effect on other links. If an enabled
 link at a sink pad prevents another link at the same pad from being disabled,
 the link_setup operation must return -EBUSY and can't implicitly disable the
 first enabled link.
+
+
+Pipelines and media streams
+---------------------------
+
+When starting streaming, drivers must notify all entities in the pipeline to
+prevent link states from being modified during streaming by calling
+
+	media_entity_pipeline_start(struct media_entity *entity,
+				    struct media_pipeline *pipe);
+
+The function will mark all entities connected to the given entity through
+enabled links, either directly or indirectly, as streaming.
+
+The media_pipeline instance pointed to by the pipe argument will be stored in
+every entity in the pipeline. Drivers should embed the media_pipeline structure
+in higher-level pipeline structures and can then access the pipeline through
+the media_entity pipe field.
+
+Calls to media_entity_pipeline_start() can be nested. The pipeline pointer must
+be identical for all nested calls to the function.
+
+When stopping the stream, drivers must notify the entities with
+
+	media_entity_pipeline_stop(struct media_entity *entity);
+
+If multiple calls to media_entity_pipeline_start() have been made the same
+number of media_entity_pipeline_stop() calls are required to stop streaming. The
+media_entity pipe field is reset to NULL on the last nested stop call.
+
+Link configuration will fail with -EBUSY by default if either end of the link is
+a streaming entity. Links that can be modified while streaming must be marked
+with the MEDIA_LNK_FL_DYNAMIC flag.
+
+If other operations need to be disallowed on streaming entities (such as
+changing entities configuration parameters) drivers can explictly check the
+media_entity stream_count field to find out if an entity is streaming. This
+operation must be done with the media_device graph_mutex held.