Update SetVariable() function description for the clarification of requirements...

Signed-off-by: Shumin Qiu <shumin.qiu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14597 6f19259b-4bc3-4df7-8a09-765794883524

diff --git a/MdePkg/Include/Uefi/UefiSpec.h b/MdePkg/Include/Uefi/UefiSpec.h
index a39b4b8960845140f969901362923dc4b4d9aa38..b44463104d9469df3fd86dce2a059ffc47968c0f 100644 (file)
--- a/MdePkg/Include/Uefi/UefiSpec.h
+++ b/MdePkg/Include/Uefi/UefiSpec.h
@@ -662,8 +662,15 @@ EFI_STATUS
                                  then EFI_INVALID_PARAMETER is returned.\r
   @param  VendorGuid             A unique identifier for the vendor.\r
   @param  Attributes             Attributes bitmask to set for the variable.\r
-  @param  DataSize               The size in bytes of the Data buffer. A size of zero causes the\r
-                                 variable to be deleted.\r
+  @param  DataSize               The size in bytes of the Data buffer. Unless the EFI_VARIABLE_APPEND_WRITE, \r
+                                 EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS, or \r
+                                 EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS attribute is set, a size of zero \r
+                                 causes the variable to be deleted. When the EFI_VARIABLE_APPEND_WRITE attribute is \r
+                                 set, then a SetVariable() call with a DataSize of zero will not cause any change to \r
+                                 the variable value (the timestamp associated with the variable may be updated however \r
+                                 even if no new data value is provided,see the description of the \r
+                                 EFI_VARIABLE_AUTHENTICATION_2 descriptor below. In this case the DataSize will not \r
+                                 be zero since the EFI_VARIABLE_AUTHENTICATION_2 descriptor will be populated). \r
   @param  Data                   The contents for the variable.\r
 \r
   @retval EFI_SUCCESS            The firmware has successfully stored the variable and its data as\r
@@ -675,9 +682,10 @@ EFI_STATUS
   @retval EFI_DEVICE_ERROR       The variable could not be retrieved due to a hardware error.\r
   @retval EFI_WRITE_PROTECTED    The variable in question is read-only.\r
   @retval EFI_WRITE_PROTECTED    The variable in question cannot be deleted.\r
-  @retval EFI_SECURITY_VIOLATION The variable could not be written due to EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS\r
-                                 set but the AuthInfo does NOT pass the validation check carried out\r
-                                 by the firmware.\r
+  @retval EFI_SECURITY_VIOLATION The variable could not be written due to EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS \r
+                                 or EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACESS being set, but the AuthInfo \r
+                                 does NOT pass the validation check carried out by the firmware.\r
+  \r
   @retval EFI_NOT_FOUND          The variable trying to be updated or deleted was not found.\r
 \r
 **/\r