[efi] Provide efi_devpath_len()

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

src/drivers/usb/usbio.c

 	path = u.interface;
 
 	/* Locate end of device path and sanity check */
-	end = efi_devpath_end ( path );
-	len = ( ( ( void * ) end ) - ( ( void * ) path ) );
+	len = efi_devpath_len ( path );
 	if ( len < sizeof ( *usbpath ) ) {
 		DBGC ( usbio, "USBIO %s underlength device path\n",
 		       efi_handle_name ( handle ) );
 		rc = -EINVAL;
 		goto err_underlength;
 	}
-	usbpath = ( ( ( void * ) end ) - sizeof ( *usbpath ) );
+	usbpath = ( ( ( void * ) path ) + len - sizeof ( *usbpath ) );
 	if ( ! ( ( usbpath->Header.Type == MESSAGING_DEVICE_PATH ) &&
 		 ( usbpath->Header.SubType == MSG_USB_DP ) ) ) {
 		DBGC ( usbio, "USBIO %s not a USB device path: ",

src/image/efi_image.c

 	size_t len;
 
 	/* Calculate device path lengths */
-	end = efi_devpath_end ( parent );
-	prefix_len = ( ( void * ) end - ( void * ) parent );
+	prefix_len = efi_devpath_len ( parent );
 	name_len = strlen ( image->name );
 	filepath_len = ( SIZE_OF_FILEPATH_DEVICE_PATH +
 			 ( name_len + 1 /* NUL */ ) * sizeof ( wchar_t ) );

src/include/ipxe/efi/efi_utils.h

 
 extern EFI_DEVICE_PATH_PROTOCOL *
 efi_devpath_end ( EFI_DEVICE_PATH_PROTOCOL *path );
+extern size_t efi_devpath_len ( EFI_DEVICE_PATH_PROTOCOL *path );
 extern int efi_locate_device ( EFI_HANDLE device, EFI_GUID *protocol,
 			       EFI_HANDLE *parent );
 extern int efi_child_add ( EFI_HANDLE parent, EFI_HANDLE child );

src/interface/efi/efi_debug.c

 efi_devpath_text ( EFI_DEVICE_PATH_PROTOCOL *path ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	static char text[256];
-	void *start;
-	void *end;
-	size_t max_len;
 	size_t len;
 	CHAR16 *wtext;
 
 	/* If we have no DevicePathToText protocol then use a raw hex string */
 	if ( ! efidpt ) {
 		DBG ( "[No DevicePathToText]" );
-		start = path;
-		end = efi_devpath_end ( path );
-		len = ( end - start );
-		max_len = ( ( sizeof ( text ) - 1 /* NUL */ ) / 2 /* "xx" */ );
-		if ( len > max_len )
-			len = max_len;
-		base16_encode ( start, len, text, sizeof ( text ) );
+		len = efi_devpath_len ( path );
+		base16_encode ( path, len, text, sizeof ( text ) );
 		return text;
 	}
 

src/interface/efi/efi_snp.c

 	}
 
 	/* Allocate the new device path */
-	path_end = efi_devpath_end ( path.path );
-	path_prefix_len = ( ( ( void * ) path_end ) - ( ( void * ) path.path ));
+	path_prefix_len = efi_devpath_len ( path.path );
 	snpdev->path = zalloc ( path_prefix_len + sizeof ( *macpath ) +
 				sizeof ( *path_end ) );
 	if ( ! snpdev->path ) {

src/interface/efi/efi_utils.c

 	return path;
 }
 
+/**
+ * Find length of device path (excluding terminator)
+ *
+ * @v path		Path to device
+ * @ret path_len	Length of device path
+ */
+size_t efi_devpath_len ( EFI_DEVICE_PATH_PROTOCOL *path ) {
+	EFI_DEVICE_PATH_PROTOCOL *end = efi_devpath_end ( path );
+
+	return ( ( ( void * ) end ) - ( ( void * ) path ) );
+}
+
 /**
  * Locate parent device supporting a given protocol
  *