[efi] Add basic EFI SAN booting capability

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

src/config/defaults/efi.h

 #define TIMER_EFI
 #define UMALLOC_EFI
 #define SMBIOS_EFI
-#define SANBOOT_NULL
+#define SANBOOT_EFI
 #define BOFM_EFI
 #define ENTROPY_EFI
 #define TIME_EFI
 #define	IMAGE_EFI		/* EFI image support */
 #define	IMAGE_SCRIPT		/* iPXE script image support */
 
+#define	SANBOOT_PROTO_ISCSI	/* iSCSI protocol */
+#define	SANBOOT_PROTO_AOE	/* AoE protocol */
+#define	SANBOOT_PROTO_IB_SRP	/* Infiniband SCSI RDMA protocol */
+#define	SANBOOT_PROTO_FCP	/* Fibre Channel protocol */
+
 #define	USB_HCD_XHCI		/* xHCI USB host controller */
 #define	USB_HCD_EHCI		/* EHCI USB host controller */
 #define	USB_HCD_UHCI		/* UHCI USB host controller */

src/include/ipxe/efi/efi_block.h

+#ifndef _IPXE_EFI_BLOCK_H
+#define _IPXE_EFI_BLOCK_H
+
+/** @block
+ *
+ * EFI block device protocols
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#ifdef SANBOOT_EFI
+#define SANBOOT_PREFIX_efi
+#else
+#define SANBOOT_PREFIX_efi __efi_
+#endif
+
+static inline __always_inline unsigned int
+SANBOOT_INLINE ( efi, san_default_drive ) ( void ) {
+	/* Drive numbers don't exist as a concept under EFI.  We
+	 * arbitarily choose to use drive 0x80 to minimise differences
+	 * with a standard BIOS.
+	 */
+	return 0x80;
+}
+
+#endif /* _IPXE_EFI_BLOCK_H */

src/include/ipxe/errfile.h

 #define ERRFILE_fault		       ( ERRFILE_CORE | 0x001f0000 )
 #define ERRFILE_blocktrans	       ( ERRFILE_CORE | 0x00200000 )
 #define ERRFILE_pixbuf		       ( ERRFILE_CORE | 0x00210000 )
+#define ERRFILE_efi_block	       ( ERRFILE_CORE | 0x00220000 )
 
 #define ERRFILE_eisa		     ( ERRFILE_DRIVER | 0x00000000 )
 #define ERRFILE_isa		     ( ERRFILE_DRIVER | 0x00010000 )

src/include/ipxe/sanboot.h

 
 /* Include all architecture-independent sanboot API headers */
 #include <ipxe/null_sanboot.h>
+#include <ipxe/efi/efi_block.h>
 
 /* Include all architecture-dependent sanboot API headers */
 #include <bits/sanboot.h>