Merge "health: drop backup instance for non-recovery." am: c900d6f20e

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/1861817

Change-Id: I40fc18ab097d711c40e19c8517e620b2d19b3fff
diff --git a/health/2.0/utils/libhealthhalutils/HealthHalUtils.cpp b/health/2.0/utils/libhealthhalutils/HealthHalUtils.cpp
index 9e1cc70..3c353e6 100644
--- a/health/2.0/utils/libhealthhalutils/HealthHalUtils.cpp
+++ b/health/2.0/utils/libhealthhalutils/HealthHalUtils.cpp
@@ -25,7 +25,26 @@
 namespace V2_0 {
 
 sp<IHealth> get_health_service() {
-    for (auto&& instanceName : {"default", "backup"}) {
+    // For the core and vendor variant, the "backup" instance points to healthd,
+    // which is removed.
+    // For the recovery variant, the "backup" instance has a different
+    // meaning. It points to android.hardware.health@2.0-impl-default.recovery
+    // which was assumed by OEMs to be always installed when a
+    // vendor-specific libhealthd is not necessary. Hence, its behavior
+    // is kept. See health/2.0/README.md.
+    // android.hardware.health@2.0-impl-default.recovery, and subsequently the
+    // special handling of recovery mode below, can be removed once health@2.1
+    // is the minimum required version (i.e. compatibility matrix level 5 is the
+    // minimum supported level). Health 2.1 requires OEMs to install the
+    // implementation to the recovery partition when it is necessary (i.e. on
+    // non-A/B devices, where IsBatteryOk() is needed in recovery).
+    for (auto&& instanceName :
+#ifdef __ANDROID_RECOVERY__
+         { "default", "backup" }
+#else
+         {"default"}
+#endif
+    ) {
         auto ret = IHealth::getService(instanceName);
         if (ret != nullptr) {
             return ret;