[edk2-platform][PATCH v1 1/7] Platforms/RaspberryPi: Fix NULL AssetTag in SMBIOS

["Samer El-Haj-Mahmoud" <samer.el-haj-mahmoud@arm.com>]

Commit 6d4fed696d004a6aeb795369aa38d4ce1d39f308 added support for
reporting AssetTag in RPi SMBIOS Types 2 and 3. The default
AssetTag is an empty string. SMBIOS does not allow empty strings to be
referenced from the corresponding string field. This caused breakage in
parsing SMBIOS Types 2 and 3 fields that follow the AssetTag field.

The issue caused an FWTS test failure, as reported in:
https://github.com/pftf/RPi4/issues/75

The fix is to detect if no AssetTag is set in the UEFI variable, and if
so, change the AssetTag SMBIOS field to an empty blank space.

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Pete Batard <pete@akeo.ie>
Cc: Andrei Warkentin <awarkentin@vmware.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Samer El-Haj-Mahmoud <samer.el-haj-mahmoud@arm.com>
---
 Platform/RaspberryPi/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Platform/RaspberryPi/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c b/Platform/RaspberryPi/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c
index d5fb843d43ce..6eef66f125f8 100644
--- a/Platform/RaspberryPi/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c
+++ b/Platform/RaspberryPi/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c
@@ -793,7 +793,13 @@ BoardInfoUpdateSmbiosType2 (
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "Failed to get Asset Tag: %r\n", Status));
   }
-  UnicodeStrToAsciiStrS(AssetTagVar, mChassisAssetTag, sizeof(mChassisAssetTag));
+
+  if (AssetTagVar[0] == L'\0') {
+    // SMBIOS referenced strings cannot be NULL. If no AssetTag is set, default to a blank space.
+    UnicodeStrToAsciiStrS(L" ", mChassisAssetTag, sizeof(mChassisAssetTag));
+  } else {
+    UnicodeStrToAsciiStrS(AssetTagVar, mChassisAssetTag, sizeof(mChassisAssetTag));
+  }
   DEBUG ((DEBUG_INFO, "System Asset Tag : %a\n", mChassisAssetTag));
 
   LogSmbiosData ((EFI_SMBIOS_TABLE_HEADER*)&mBoardInfoType2, mBoardInfoType2Strings, NULL);
-- 
2.17.1