encore: fix accidental formatting of /boot partition

When emmc and sdcard share device major number, vold can pick
the wrong device based on partion nodes alone. This adds an override
to use device node mapping instead.

Change-Id: Icb9b301c278656631aa9db5c2ca09b11da870794

Android.mk

@@ -55,6 +55,10 @@ ifneq ($(BOARD_VOLD_MAX_PARTITIONS),)
 LOCAL_CFLAGS += -DVOLD_MAX_PARTITIONS=$(BOARD_VOLD_MAX_PARTITIONS)
 endif
 
+ifeq ($(BOARD_VOLD_EMMC_SHARES_DEV_MAJOR), true)
+LOCAL_CFLAGS += -DVOLD_EMMC_SHARES_DEV_MAJOR
+endif
+
 ifneq ($(TARGET_USE_CUSTOM_LUN_FILE_PATH),)
 LOCAL_CFLAGS += -DCUSTOM_LUN_FILE=\"$(TARGET_USE_CUSTOM_LUN_FILE_PATH)\"
 endif

Volume.cpp

@@ -233,6 +233,15 @@ int Volume::formatVol() {
     sprintf(devicePath, "/dev/block/vold/%d:%d",
             MAJOR(partNode), MINOR(partNode));
 
+#ifdef VOLD_EMMC_SHARES_DEV_MAJOR
+    // If emmc and sdcard share dev major number, vold may pick
+    // incorrectly based on partition nodes alone, formatting
+    // the wrong device. Use device nodes instead.
+    dev_t deviceNodes;
+    getDeviceNodes((dev_t *) &deviceNodes, 1);
+    sprintf(devicePath, "/dev/block/vold/%d:%d", MAJOR(deviceNodes), MINOR(deviceNodes));
+#endif
+
     if (mDebug) {
         SLOGI("Formatting volume %s (%s)", getLabel(), devicePath);
     }