Function sysctl_add_oid

freebsd/kern/kern_sysctl.c:824–874

* Create new sysctls at run time. * clist may point to a valid context initialized with sysctl_ctx_init(). */

 * clist may point to a valid context initialized with sysctl_ctx_init().
 */
struct sysctl_oid *
sysctl_add_oid(struct sysctl_ctx_list *clist, struct sysctl_oid_list *parent,
	int number, const char *name, int kind, void *arg1, intmax_t arg2,
	int (*handler)(SYSCTL_HANDLER_ARGS), const char *fmt, const char *descr,
	const char *label)
{
	struct sysctl_oid *oidp;

	/* You have to hook up somewhere.. */
	if (parent == NULL)
		return(NULL);
	/* Check if the node already exists, otherwise create it */
	SYSCTL_WLOCK();
	oidp = sysctl_find_oidname(name, parent);
	if (oidp != NULL) {
		if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
			oidp->oid_refcnt++;
			/* Update the context */
			if (clist != NULL)
				sysctl_ctx_entry_add(clist, oidp);
			SYSCTL_WUNLOCK();
			return (oidp);
		} else {
			sysctl_warn_reuse(__func__, oidp);
			SYSCTL_WUNLOCK();
			return (NULL);
		}
	}
	oidp = malloc(sizeof(struct sysctl_oid), M_SYSCTLOID, M_WAITOK|M_ZERO);
	oidp->oid_parent = parent;
	SLIST_INIT(&oidp->oid_children);
	oidp->oid_number = number;
	oidp->oid_refcnt = 1;
	oidp->oid_name = strdup(name, M_SYSCTLOID);
	oidp->oid_handler = handler;
	oidp->oid_kind = CTLFLAG_DYN | kind;
	oidp->oid_arg1 = arg1;
	oidp->oid_arg2 = arg2;
	oidp->oid_fmt = fmt;
	if (descr != NULL)
		oidp->oid_descr = strdup(descr, M_SYSCTLOID);
	if (label != NULL)
		oidp->oid_label = strdup(label, M_SYSCTLOID);
	/* Update the context, if used */
	if (clist != NULL)
		sysctl_ctx_entry_add(clist, oidp);
	/* Register this oid */
	sysctl_register_oid(oidp);
	SYSCTL_WUNLOCK();
	return (oidp);
}

/*
 * Rename an existing oid.