android, controls: Add and plumb MaxLatency control

Add a MaxLatency control, and plumb it into the HAL accordingly.

Bug: https://bugs.libcamera.org/show_bug.cgi?id=50
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/android/camera_capabilities.cpp

@@ -1119,8 +1119,10 @@ int CameraCapabilities::initializeStaticMetadata()
 	}
 
 	/* Sync static metadata. */
-	int32_t maxLatency = ANDROID_SYNC_MAX_LATENCY_UNKNOWN;
-	staticMetadata_->addEntry(ANDROID_SYNC_MAX_LATENCY, maxLatency);
+	setMetadata(staticMetadata_.get(), ANDROID_SYNC_MAX_LATENCY,
+		    controlsInfo, controls::draft::MaxLatency,
+		    ControlRange::Def,
+		    ANDROID_SYNC_MAX_LATENCY_UNKNOWN);
 
 	/* Flash static metadata. */
 	char flashAvailable = ANDROID_FLASH_INFO_AVAILABLE_FALSE;

src/libcamera/control_ids.yaml

@@ -622,6 +622,16 @@ controls:
         detection, additional format conversions etc) count as an additional
         pipeline stage.
 
+  - MaxLatency:
+      type: int32_t
+      draft: true
+      description: |
+        The maximum number of frames that can occur after a request (different
+        than the previous) has been submitted, and before the result's state
+        becomes synchronized. A value of -1 indicates unknown latency, and 0
+        indicates per-frame control. Currently identical to
+        ANDROID_SYNC_MAX_LATENCY.
+
   - TestPatternMode:
       type: int32_t
       draft: true