Add some updates to documentation regarding concurrent camera operation.

- Add documentation about giving hints to camera HAL about concurrent
  operation before configuring sessions

- Limitations on ZOOM_RATIO_RANGE during concurrent operation.

Bug: 151891611

Test: builds

Change-Id: I79d0bd8be1ed9aa29a1ba080d01833f16eff580c
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>
diff --git a/camera/provider/2.6/ICameraProvider.hal b/camera/provider/2.6/ICameraProvider.hal
index ed1d31d..b8873a6 100644
--- a/camera/provider/2.6/ICameraProvider.hal
+++ b/camera/provider/2.6/ICameraProvider.hal
@@ -76,12 +76,16 @@
      * configuration settings exposed through camera metadata), should the sum
      * of resource costs for the combination be <= 100.
      *
-     * The lists of camera id combinations returned by this method may contain
-     * hidden physical camera ids. If a combination does contain hidden physical
-     * camera ids, the camera framework must be able to open any logical cameras
-     * that contain these hidden physical camera ids in their
-     * ANDROID_LOGICAL_MULTI_CAMERA_PHYSICAL_IDS list, in addition to the other
-     * camera ids advertised in the combination, for concurrent operation.
+     * For guaranteed concurrent camera operation, the camera framework must call
+     * ICameraDevice.open() on all devices (intended for concurrent operation), before configuring
+     * any streams on them. This gives the camera HAL process an opportunity to potentially
+     * distribute hardware resources better before stream configuration.
+     *
+     * Due to potential hardware constraints around internal switching of physical camera devices,
+     * a device's complete ZOOM_RATIO_RANGE(if supported), may not apply during concurrent
+     * operation. If ZOOM_RATIO is supported, camera HALs must ensure ZOOM_RATIO_RANGE of
+     * [1.0, ANDROID_SCALER_AVAILABLE_MAX_DIGITAL_ZOOM] is supported by that device, during
+     * concurrent operation.
      *
      * @return status Status code for the operation
      * @return cameraIds a list of camera id combinations that support