diff --git a/common/boot_control_interface.h b/common/boot_control_interface.h
index c93de5c..3b61add 100644
--- a/common/boot_control_interface.h
+++ b/common/boot_control_interface.h
@@ -75,6 +75,11 @@
                                   Slot slot,
                                   std::string* device) const = 0;
 
+  virtual std::optional<PartitionDevice> GetPartitionDevice(
+      const std::string& partition_name,
+      uint32_t slot,
+      uint32_t current_slot,
+      bool not_in_payload = false) const = 0;
   // Returns whether the passed |slot| is marked as bootable. Returns false if
   // the slot is invalid.
   virtual bool IsSlotBootable(Slot slot) const = 0;
diff --git a/common/boot_control_stub.cc b/common/boot_control_stub.cc
index 907f670..a1cc055 100644
--- a/common/boot_control_stub.cc
+++ b/common/boot_control_stub.cc
@@ -44,6 +44,15 @@
   return false;
 }
 
+std::optional<PartitionDevice> BootControlStub::GetPartitionDevice(
+    const std::string& partition_name,
+    uint32_t slot,
+    uint32_t current_slot,
+    bool not_in_payload) const {
+  LOG(ERROR) << __FUNCTION__ << " should never be called.";
+  return {};
+}
+
 bool BootControlStub::GetPartitionDevice(const string& partition_name,
                                          Slot slot,
                                          string* device) const {
diff --git a/common/boot_control_stub.h b/common/boot_control_stub.h
index a1bdb96..dcddbae 100644
--- a/common/boot_control_stub.h
+++ b/common/boot_control_stub.h
@@ -48,6 +48,11 @@
   bool GetPartitionDevice(const std::string& partition_name,
                           BootControlInterface::Slot slot,
                           std::string* device) const override;
+  std::optional<PartitionDevice> GetPartitionDevice(
+      const std::string& partition_name,
+      uint32_t slot,
+      uint32_t current_slot,
+      bool not_in_payload = false) const override;
   bool IsSlotBootable(BootControlInterface::Slot slot) const override;
   bool MarkSlotUnbootable(BootControlInterface::Slot slot) override;
   bool SetActiveBootSlot(BootControlInterface::Slot slot) override;
diff --git a/common/dynamic_partition_control_interface.h b/common/dynamic_partition_control_interface.h
index 1362c19..855d6e8 100644
--- a/common/dynamic_partition_control_interface.h
+++ b/common/dynamic_partition_control_interface.h
@@ -36,6 +36,12 @@
 
 namespace chromeos_update_engine {
 
+struct PartitionDevice {
+  std::string rw_device_path;
+  std::string mountable_device_path;
+  bool is_dynamic;
+};
+
 struct FeatureFlag {
   enum class Value { NONE = 0, RETROFIT, LAUNCH };
   constexpr explicit FeatureFlag(Value value) : value_(value) {}
diff --git a/common/fake_boot_control.h b/common/fake_boot_control.h
index 98b93e6..fc7839d 100644
--- a/common/fake_boot_control.h
+++ b/common/fake_boot_control.h
@@ -51,14 +51,16 @@
                           bool not_in_payload,
                           std::string* device,
                           bool* is_dynamic) const override {
-    if (slot >= num_slots_)
+    auto dev =
+        GetPartitionDevice(partition_name, slot, current_slot_, not_in_payload);
+    if (!dev.has_value()) {
       return false;
-    auto part_it = devices_[slot].find(partition_name);
-    if (part_it == devices_[slot].end())
-      return false;
-    *device = part_it->second;
-    if (is_dynamic != nullptr) {
-      *is_dynamic = false;
+    }
+    if (is_dynamic) {
+      *is_dynamic = dev->is_dynamic;
+    }
+    if (device) {
+      *device = dev->rw_device_path;
     }
     return true;
   }
@@ -120,6 +122,25 @@
     return dynamic_partition_control_.get();
   }
 
+  std::optional<PartitionDevice> GetPartitionDevice(
+      const std::string& partition_name,
+      uint32_t slot,
+      uint32_t current_slot,
+      bool not_in_payload = false) const override {
+    if (slot >= devices_.size()) {
+      return {};
+    }
+    auto device_path = devices_[slot].find(partition_name);
+    if (device_path == devices_[slot].end()) {
+      return {};
+    }
+    PartitionDevice device;
+    device.is_dynamic = false;
+    device.rw_device_path = device_path->second;
+    device.mountable_device_path = device.rw_device_path;
+    return device;
+  }
+
  private:
   BootControlInterface::Slot num_slots_{2};
   BootControlInterface::Slot current_slot_{0};