Post commit readiness latch to smbios grpc

Port downstream patch
https://gbmc-private-review.git.corp.google.com/c/meta-fii-google/+/97105
to shared code

PiperOrigin-RevId: 969568786
Change-Id: I0f97ad883f14a4180182e31b741d0e1d100e09fb

src/smbios_callback.cc

diff --git a/src/smbios_callback.cc b/src/smbios_callback.cc
index a23c9b3..88ff115 100644
--- a/src/smbios_callback.cc
+++ b/src/smbios_callback.cc
@@ -7,11 +7,14 @@
 
 #include <cerrno>
 #include <cstring>
+#include <system_error> // NOLINT
+#include <filesystem> // NOLINT
 #include <fstream>
 #include <string>
 #include <utility>
 
 #include "absl/log/log.h"
+#include "absl/strings/str_cat.h"
 #include "smbios_file.h"
 #include "grpcpp/server_context.h"
 #include "grpcpp/support/status.h"
@@ -99,12 +102,50 @@
       LOG(ERROR) << "Could not save SMBIOS to file: " << fileName;
       return;
     }
-    LOG(INFO) << "smbos file saved " << fileName;
+    LOG(INFO) << "smbios file saved " << fileName;
+
+    writeStatusLatch();
   }
 
   sendSignalToSmbiosApp();
 }
 
+void SmbiosTransferServiceImpl::writeStatusLatch() {
+  std::string finalStatusFilePath = absl::StrCat(
+      basePath_, "/run/smbios-mdr/status-host-", std::to_string(instance + 1));
+  std::string tempStatusFilePath = finalStatusFilePath + ".tmp";
+
+  std::filesystem::path statusDir =
+      std::filesystem::path(finalStatusFilePath).parent_path();
+  std::error_code ec;
+  std::filesystem::create_directories(statusDir, ec);
+  if (ec) {
+    LOG(ERROR) << "Unable to make directory " << statusDir
+               << ": " << ec.message();
+    return;
+  }
+
+  std::ofstream tempFile(tempStatusFilePath);
+  if (!tempFile.is_open()) {
+    LOG(ERROR) << "Unable to open temporary status file for writing: "
+               << tempStatusFilePath;
+    return;
+  }
+
+  tempFile << "NEW";
+  tempFile.close();
+
+  std::filesystem::rename(tempStatusFilePath, finalStatusFilePath, ec);
+  if (ec) {
+    LOG(ERROR) << "Failed to atomically rename status file from "
+               << tempStatusFilePath << " to " << finalStatusFilePath
+               << ": " << ec.message();
+    return;
+  }
+
+  LOG(INFO) << "Status file successfully written to " << finalStatusFilePath;
+}
+
 void SmbiosTransferServiceImpl::sendSignalToSmbiosApp() {
   LOG(INFO) << "Attempting to send Signal to smbiosmdrv2app for instance "
             << instance;

src/smbios_callback.h

diff --git a/src/smbios_callback.h b/src/smbios_callback.h
index 6e083bc..04d2be0 100644
--- a/src/smbios_callback.h
+++ b/src/smbios_callback.h
@@ -32,6 +32,7 @@
  protected:
   [[nodiscard]] bool claimLinkBusy();
   void writeThenStart(const SmbiosEntry& entry, bool isWrite);
+  void writeStatusLatch();
   void sendSignalToSmbiosApp();
 
  private: