EFI_ACPI_6_0_GTDT_GT_BLOCK_COMMON_FLAG_ALWAYS_ON_CAPABILITY

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
extern (C)
enum EFI_ACPI_6_0_GTDT_GT_BLOCK_COMMON_FLAG_ALWAYS_ON_CAPABILITY = BIT1;

Meta