[block] Allow SAN boot device to be identified by UUID

Add a "--uuid" option which may be used to specify a boot device UUID,
to be matched against the GPT partition GUID.

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

src/include/ipxe/parseopt.h

@@ -126,10 +126,18 @@ struct named_setting {
 	struct setting setting;
 };
 
+/** A UUID command-line option */
+struct uuid_option {
+	/** UUID */
+	union uuid *value;
+	/** Storage buffer */
+	union uuid buf;
+};
+
 extern int parse_string ( char *text, char **value );
 extern int parse_integer ( char *text, unsigned int *value );
 extern int parse_timeout ( char *text, unsigned long *value );
-extern int parse_uuid ( char *text, union uuid *value );
+extern int parse_uuid ( char *text, struct uuid_option *uuid );
 extern int parse_netdev ( char *text, struct net_device **netdev );
 extern int
 parse_netdev_configurator ( char *text,

src/include/ipxe/sanboot.h

@@ -19,6 +19,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <ipxe/process.h>
 #include <ipxe/blockdev.h>
 #include <ipxe/acpi.h>
+#include <ipxe/uuid.h>
 #include <config/sanboot.h>
 
 /**
@@ -109,6 +110,8 @@ enum san_device_flags {
 struct san_boot_config {
 	/** Boot filename (or NULL to use default) */
 	const char *filename;
+	/** UUID (or NULL to ignore UUID) */
+	union uuid *uuid;
 };
 
 /**