acpi_hw_get_mode
u32 acpi_hw_get_mode(void);
if (acpi_hw_get_mode() == ACPI_SYS_MODE_LEGACY) {
if (acpi_hw_get_mode() == ACPI_SYS_MODE_ACPI) {
if (acpi_hw_get_mode() == ACPI_SYS_MODE_ACPI) {
acpi_gbl_original_mode = acpi_hw_get_mode();