[efi] Provide access to ACPI tables

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/interface/efi/efi_acpi.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2017 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/**
+ * @file
+ *
+ * iPXE ACPI API for EFI
+ *
+ */
+
+#include <ipxe/acpi.h>
+#include <ipxe/efi/efi.h>
+#include <ipxe/efi/Guid/Acpi.h>
+#include <ipxe/efi/efi_acpi.h>
+
+/** ACPI configuration table */
+static EFI_ACPI_1_0_ROOT_SYSTEM_DESCRIPTION_POINTER *rsdp;
+EFI_USE_TABLE ( ACPI_10_TABLE, &rsdp, 0 );
+
+/**
+ * Locate ACPI root system description table
+ *
+ * @ret rsdt		ACPI root system description table, or UNULL
+ */
+static userptr_t efi_find_rsdt ( void ) {
+
+	/* Locate RSDT via ACPI configuration table, if available */
+	if ( rsdp )
+		return phys_to_user ( rsdp->RsdtAddress );
+
+	return UNULL;
+}
+
+PROVIDE_ACPI ( efi, acpi_find_rsdt, efi_find_rsdt );