Add support for writeBlocking

Adds support for the Sensors HAL to use writeBlocking when sending
sensor events to the framework.

Bug: 111070257
Test: Builds, verified that if the default implementation is modified
      to use a writeBlocking call, the framework receives events, and
      the HAL blocks if the Event FMQ is full.
Change-Id: I62fc654513afe98901b1e65bdf422af276d22663
diff --git a/sensors/2.0/types.hal b/sensors/2.0/types.hal
index e1a029a..f9defa2 100644
--- a/sensors/2.0/types.hal
+++ b/sensors/2.0/types.hal
@@ -29,4 +29,14 @@
      * Used to notify the Event FMQ that events should be read and processed.
      */
     READ_AND_PROCESS = 1 << 0,
+
+    /**
+     * Used by the framework to signal to the HAL when events have been
+     * successfully read from the Event FMQ.
+     *
+     * If the MessageQueue::writeBlocking function is being used to write sensor
+     * events to the Event FMQ, then the readNotification parameter must be set
+     * to EVENTS_READ.
+     */
+     EVENTS_READ = 1 << 1,
 };