[autoboot] Enable infrastructure to specify an autoboot device location

iPXE will currently attempt to boot from every network device for
which it has a driver.  Where a system has more than one network
device supported by iPXE, this renders BIOS IPL lists ineffective.

Allow an autoboot device location to be specified.  If such a location
is specified, then only devices matching that location will be used as
part of the automatic boot sequence.  If no such location is
specified, then all devices will be used.

Note that this does not affect the "autoboot" command, which will
continue to use all devices.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Modified-by: Michael Brown <mcb30@ipxe.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/usr/autoboot.h

 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <ipxe/in.h>
+#include <ipxe/device.h>
 struct net_device;
 struct uri;
 struct settings;
 			 URIBOOT_NO_SAN_BOOT |	   \
 			 URIBOOT_NO_SAN_UNHOOK )
 
+extern struct device_description autoboot_device;
+
 extern int uriboot ( struct uri *filename, struct uri *root_path, int drive,
 		     unsigned int flags );
 extern struct uri *
 fetch_next_server_and_filename ( struct settings *settings );
 extern int netboot ( struct net_device *netdev );
-extern int autoboot ( void );
 extern void ipxe ( struct net_device *netdev );
 
 extern int pxe_menu_boot ( struct net_device *netdev );

src/usr/autoboot.c

  *
  */
 
+/** Device location of preferred autoboot device */
+struct device_description autoboot_device;
+
 /* Disambiguate the various error causes */
 #define ENOENT_BOOT __einfo_error ( EINFO_ENOENT_BOOT )
 #define EINFO_ENOENT_BOOT \
 	return -ENOTSUP;
 }
 
-/**
- * Identify the boot network device
- *
- * @ret netdev		Boot network device
- */
-static struct net_device * find_boot_netdev ( void ) {
-	return NULL;
-}
-
 /**
  * Parse next-server and filename into a URI
  *
 	return rc;
 }
 
+/**
+ * Test if network device matches the autoboot device location
+ *
+ * @v netdev		Network device
+ * @ret is_autoboot	Network device matches the autoboot device location
+ */
+static int is_autoboot_device ( struct net_device *netdev ) {
+
+	return ( ( netdev->dev->desc.bus_type == autoboot_device.bus_type ) &&
+		 ( netdev->dev->desc.location == autoboot_device.location ) );
+}
+
 /**
  * Boot the system
  */
-int autoboot ( void ) {
-	struct net_device *boot_netdev;
+static int autoboot ( void ) {
 	struct net_device *netdev;
 	int rc = -ENODEV;
 
-	/* If we have an identifable boot device, try that first */
-	if ( ( boot_netdev = find_boot_netdev() ) )
-		rc = netboot ( boot_netdev );
-
-	/* If that fails, try booting from any of the other devices */
+	/* Try booting from each network device.  If we have a
+	 * specified autoboot device location, then use only devices
+	 * matching that location.
+	 */
 	for_each_netdev ( netdev ) {
-		if ( netdev == boot_netdev )
+
+		/* Skip any non-matching devices, if applicable */
+		if ( autoboot_device.bus_type &&
+		     ( ! is_autoboot_device ( netdev ) ) )
 			continue;
+
+		/* Attempt booting from this device */
 		rc = netboot ( netdev );
 	}