1 files changed, 33 insertions, 0 deletions
diff --git a/sys/dev/vmm/vmm_param.h b/sys/dev/vmm/vmm_param.h
new file mode 100644
index 000000000000..a5040eb0f58c
--- /dev/null
+++ b/sys/dev/vmm/vmm_param.h
@@ -0,0 +1,33 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2011 NetApp, Inc.
+ * All rights reserved.
+ */
+
+#ifndef _DEV_VMM_PARAM_H_
+#define	_DEV_VMM_PARAM_H_
+
+/*
+ * The VM name has to fit into the pathname length constraints of devfs,
+ * governed primarily by SPECNAMELEN.  The length is the total number of
+ * characters in the full path, relative to the mount point and not
+ * including any leading '/' characters.
+ * A prefix and a suffix are added to the name specified by the user.
+ * The prefix is usually "vmm/" or "vmm.io/", but can be a few characters
+ * longer for future use.
+ * The suffix is a string that identifies a bootrom image or some similar
+ * image that is attached to the VM. A separator character gets added to
+ * the suffix automatically when generating the full path, so it must be
+ * accounted for, reducing the effective length by 1.
+ * The effective length of a VM name is 229 bytes for FreeBSD 13 and 37
+ * bytes for FreeBSD 12.  A minimum length is set for safety and supports
+ * a SPECNAMELEN as small as 32 on old systems.
+ */
+#define	VM_MAX_PREFIXLEN	10
+#define	VM_MAX_SUFFIXLEN	15
+#define	VM_MIN_NAMELEN		6
+#define	VM_MAX_NAMELEN		\
+	(SPECNAMELEN - VM_MAX_PREFIXLEN - VM_MAX_SUFFIXLEN - 1)
+
+#endif /* !_DEV_VMM_PARAM_H_ */