Intel Extensible Firmware Interface - Manual (Page 199)

Services — Runtime Services
Version 1.10 12/01/02 6-7
SetVariable()
Summary
Sets the value of a variable.
Prototype
EFI_STATUS
SetVariable (
IN CHAR16 *VariableName,
IN EFI_GUID *VendorGuid,
IN UINT32 Attributes,
IN UINTN DataSize,
IN VOID *Data
);
Parameters
VariableName A Null-terminated Unicode string that is the name of the
vendor’s variable. Each
VariableName is unique for each
VendorGuid . VariableName must contain 1 or more
Unicode characters. If VariableName is an empty Unicode
string, then EFI_INVALID_PARAMETER is returned.
VendorGuid A unique identifier for the vendor. Type EFI_GUID is defined
in the InstallProtocolInterface() function
description.
Attributes Attributes bitmask to set for the variable. Refer to the
GetVariable() function description.
DataSize The size in bytes of the Data buffer. A size of zero causes the
variable to be deleted.
Data The contents for the variable.
Description
Variables are stored by the firmware and may maintain their values across power cycles. Each
vendor may create and manage its own variables without the risk of name conflicts by using a
unique
VendorGuid .
Each variable has Attributes that define how the firmware stores and maintains the data value.
If the EFI_VARIABLE_NON_VOLATILE attribute is not set, the firmware stores the variable in
normal memory and it is not maintained across a power cycle. Such variables are used to pass
information from one component to another. An example of this is the firmware’s language code