init: Unify duplicated get_android_dt_dir with libfs_mgr

init and libfs_mgr both defines get_android_dt_dir() with subtle
differences. Merge the two implementations into libfs_mgr to reduce code
duplication (in terms of source code and code gen)

Note:
init's implementation checks the kernel cmdline first and then the
kernel bootconfig, while libfs_mgr's order is the opposite.
Realistically I don't think this order matter much though. If any, we
should prioritize bootconfig over kernel cmdline most of the time.

Bug: 293695109
Test: Presubmit
Merged-In: Ic8d2c965c62f9e873ccdaf77d67c7708f25a7b56
Change-Id: Ic8d2c965c62f9e873ccdaf77d67c7708f25a7b56
diff --git a/init/util.cpp b/init/util.cpp
index d0478e8..61d59a4 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -42,6 +42,10 @@
 #include <cutils/sockets.h>
 #include <selinux/android.h>
 
+#if defined(__ANDROID__)
+#include <fs_mgr.h>
+#endif
+
 #ifdef INIT_FULL_SOURCES
 #include <android/api-level.h>
 #include <sys/system_properties.h>
@@ -60,8 +64,6 @@
 namespace android {
 namespace init {
 
-const std::string kDefaultAndroidDtDir("/proc/device-tree/firmware/android/");
-
 const std::string kDataDirPrefix("/data/");
 
 void (*trigger_shutdown)(const std::string& command) = nullptr;
@@ -375,45 +377,18 @@
     return dst;
 }
 
-static std::string init_android_dt_dir() {
-    // Use the standard procfs-based path by default
-    std::string android_dt_dir = kDefaultAndroidDtDir;
-    // The platform may specify a custom Android DT path in kernel cmdline
-    ImportKernelCmdline([&](const std::string& key, const std::string& value) {
-        if (key == "androidboot.android_dt_dir") {
-            android_dt_dir = value;
-        }
-    });
-    // ..Or bootconfig
-    if (android_dt_dir == kDefaultAndroidDtDir) {
-        ImportBootconfig([&](const std::string& key, const std::string& value) {
-            if (key == "androidboot.android_dt_dir") {
-                android_dt_dir = value;
-            }
-        });
-    }
-
-    LOG(INFO) << "Using Android DT directory " << android_dt_dir;
-    return android_dt_dir;
-}
-
-// FIXME: The same logic is duplicated in system/core/fs_mgr/
-const std::string& get_android_dt_dir() {
-    // Set once and saves time for subsequent calls to this function
-    static const std::string kAndroidDtDir = init_android_dt_dir();
-    return kAndroidDtDir;
-}
-
 // Reads the content of device tree file under the platform's Android DT directory.
 // Returns true if the read is success, false otherwise.
 bool read_android_dt_file(const std::string& sub_path, std::string* dt_content) {
-    const std::string file_name = get_android_dt_dir() + sub_path;
+#if defined(__ANDROID__)
+    const std::string file_name = android::fs_mgr::GetAndroidDtDir() + sub_path;
     if (android::base::ReadFileToString(file_name, dt_content)) {
         if (!dt_content->empty()) {
             dt_content->pop_back();  // Trims the trailing '\0' out.
             return true;
         }
     }
+#endif
     return false;
 }