Revert "Revert "ueventd: remove PlatformDeviceList""

This reverts commit 516ff99711bbb533c4ca3970882ef376df6b044d.

Bug: 62864413
Bug: 62864413

Merged-In: Ie3980cd536c2c83adace063f0950128f68561105
Change-Id: Ie3980cd536c2c83adace063f0950128f68561105
Signed-off-by: Sandeep Patil <sspatil@google.com>
(cherry picked from commit cd2ba0d184c3fa9bbf0881a5d1fb3d3e205da1f9)
diff --git a/init/devices.cpp b/init/devices.cpp
index c52d8f8..2943fb7 100644
--- a/init/devices.cpp
+++ b/init/devices.cpp
@@ -147,21 +147,34 @@
     }
 }
 
-// Given a path that may start with a platform device, find the length of the
-// platform device prefix.  If it doesn't start with a platform device, return false
-bool PlatformDeviceList::Find(const std::string& path, std::string* out_path) const {
-    out_path->clear();
-    // platform_devices is searched backwards, since parents are added before their children,
-    // and we want to match as deep of a child as we can.
-    for (auto it = platform_devices_.crbegin(); it != platform_devices_.crend(); ++it) {
-        auto platform_device_path_length = it->length();
-        if (platform_device_path_length < path.length() &&
-            path[platform_device_path_length] == '/' &&
-            android::base::StartsWith(path, it->c_str())) {
-            *out_path = *it;
+// Given a path that may start with a platform device, find the parent platform device by finding a
+// parent directory with a 'subsystem' symlink that points to the platform bus.
+// If it doesn't start with a platform device, return false
+bool DeviceHandler::FindPlatformDevice(std::string path, std::string* platform_device_path) const {
+    platform_device_path->clear();
+
+    // Uevents don't contain the mount point, so we need to add it here.
+    path.insert(0, sysfs_mount_point_);
+
+    std::string directory = android::base::Dirname(path);
+
+    while (directory != "/" && directory != ".") {
+        std::string subsystem_link_path;
+        if (android::base::Realpath(directory + "/subsystem", &subsystem_link_path) &&
+            subsystem_link_path == sysfs_mount_point_ + "/bus/platform") {
+            // We need to remove the mount point that we added above before returning.
+            directory.erase(0, sysfs_mount_point_.size());
+            *platform_device_path = directory;
             return true;
         }
+
+        auto last_slash = path.rfind('/');
+        if (last_slash == std::string::npos) return false;
+
+        path.erase(last_slash);
+        directory = android::base::Dirname(path);
     }
+
     return false;
 }
 
@@ -258,7 +271,7 @@
 
 std::vector<std::string> DeviceHandler::GetCharacterDeviceSymlinks(const Uevent& uevent) const {
     std::string parent_device;
-    if (!platform_devices_.Find(uevent.path, &parent_device)) return {};
+    if (!FindPlatformDevice(uevent.path, &parent_device)) return {};
 
     // skip path to the parent driver
     std::string path = uevent.path.substr(parent_device.length());
@@ -316,7 +329,7 @@
     std::string device;
     std::string type;
 
-    if (platform_devices_.Find(uevent.path, &device)) {
+    if (FindPlatformDevice(uevent.path, &device)) {
         // Skip /devices/platform or /devices/ if present
         static const std::string devices_platform_prefix = "/devices/platform/";
         static const std::string devices_prefix = "/devices/";
@@ -388,14 +401,6 @@
     }
 }
 
-void DeviceHandler::HandlePlatformDeviceEvent(const Uevent& uevent) {
-    if (uevent.action == "add") {
-        platform_devices_.Add(uevent.path);
-    } else if (uevent.action == "remove") {
-        platform_devices_.Remove(uevent.path);
-    }
-}
-
 void DeviceHandler::HandleBlockDeviceEvent(const Uevent& uevent) const {
     // if it's not a /dev device, nothing to do
     if (uevent.major < 0 || uevent.minor < 0) return;
@@ -458,8 +463,6 @@
 
     if (uevent.subsystem == "block") {
         HandleBlockDeviceEvent(uevent);
-    } else if (uevent.subsystem == "platform") {
-        HandlePlatformDeviceEvent(uevent);
     } else {
         HandleGenericDeviceEvent(uevent);
     }
@@ -472,7 +475,8 @@
       sysfs_permissions_(std::move(sysfs_permissions)),
       subsystems_(std::move(subsystems)),
       sehandle_(selinux_android_file_context_handle()),
-      skip_restorecon_(skip_restorecon) {}
+      skip_restorecon_(skip_restorecon),
+      sysfs_mount_point_("/sys") {}
 
 DeviceHandler::DeviceHandler()
     : DeviceHandler(std::vector<Permissions>{}, std::vector<SysfsPermissions>{},