From a183d81dc9f985f94974a821886cd57bd784480f Mon Sep 17 00:00:00 2001
From: "Stephen J. Kiernan" <stevek@FreeBSD.org>
Date: Sat, 6 Aug 2016 18:48:47 +0000
Subject: [PATCH] Add hw.fdt sysctl node. Make FDT blob available via opaque
 hw.fdt.dtb sysctl, if a DTB has been installed by the time sysctls are
 registered.

Reviewed by:	andrew
Approved by:	sjg (mentor)
Sponsored by:	Juniper Networks, Inc.
Differential Revision:	https://reviews.freebsd.org/D7411
---
 sys/dev/fdt/fdt_common.c |  3 +++
 sys/dev/fdt/fdt_common.h |  3 +++
 sys/dev/ofw/ofw_fdt.c    | 21 +++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/sys/dev/fdt/fdt_common.c b/sys/dev/fdt/fdt_common.c
index 4e0d6e206c5b..2f4555f81a4d 100644
--- a/sys/dev/fdt/fdt_common.c
+++ b/sys/dev/fdt/fdt_common.c
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/bus.h>
 #include <sys/limits.h>
+#include <sys/sysctl.h>
 
 #include <machine/resource.h>
 
@@ -60,6 +61,8 @@ __FBSDID("$FreeBSD$");
 
 #define FDT_REG_CELLS	4
 
+SYSCTL_NODE(_hw, OID_AUTO, fdt, CTLFLAG_RD, 0, "Flattened Device Tree");
+
 vm_paddr_t fdt_immr_pa;
 vm_offset_t fdt_immr_va;
 vm_offset_t fdt_immr_size;
diff --git a/sys/dev/fdt/fdt_common.h b/sys/dev/fdt/fdt_common.h
index 94f84ff3fe49..afddc310c127 100644
--- a/sys/dev/fdt/fdt_common.h
+++ b/sys/dev/fdt/fdt_common.h
@@ -32,6 +32,7 @@
 #ifndef _FDT_COMMON_H_
 #define _FDT_COMMON_H_
 
+#include <sys/sysctl.h>
 #include <sys/slicer.h>
 #include <contrib/libfdt/libfdt_env.h>
 #include <dev/ofw/ofw_bus.h>
@@ -80,6 +81,8 @@ extern struct fdt_pm_mask_entry fdt_pm_mask_table[];
 extern u_char fdt_static_dtb;
 #endif
 
+SYSCTL_DECL(_hw_fdt);
+
 int fdt_addrsize_cells(phandle_t, int *, int *);
 u_long fdt_data_get(void *, int);
 int fdt_data_to_res(pcell_t *, int, int, u_long *, u_long *);
diff --git a/sys/dev/ofw/ofw_fdt.c b/sys/dev/ofw/ofw_fdt.c
index fc41d5bc6a3c..0f7cf07919b3 100644
--- a/sys/dev/ofw/ofw_fdt.c
+++ b/sys/dev/ofw/ofw_fdt.c
@@ -95,6 +95,27 @@ OFW_DEF(ofw_fdt);
 
 static void *fdtp = NULL;
 
+static int
+sysctl_handle_dtb(SYSCTL_HANDLER_ARGS)
+{
+
+        return (sysctl_handle_opaque(oidp, fdtp, fdt_totalsize(fdtp), req));
+}
+
+static void
+sysctl_register_fdt_oid(void *arg)
+{
+
+	/* If there is no FDT registered, skip adding the sysctl */
+	if (fdtp == NULL)
+		return;
+
+	SYSCTL_ADD_PROC(NULL, SYSCTL_STATIC_CHILDREN(_hw_fdt), OID_AUTO, "dtb",
+	    CTLTYPE_OPAQUE | CTLFLAG_RD, NULL, 0, sysctl_handle_dtb, "",
+	    "Device Tree Blob");
+}
+SYSINIT(dtb_oid, SI_SUB_KMEM, SI_ORDER_ANY, sysctl_register_fdt_oid, 0);
+
 static int
 ofw_fdt_init(ofw_t ofw, void *data)
 {