Use generated sysdown() function

NOTE: This commit requires a newt tool update
(dfaede5fbdd0c9d798714abed77b54be2d26bc06).

Upon application-triggered restart, execute each package's shutdown
subprocedure.  This feature is discussed here:
https://lists.apache.org/thread.html/ebd53c9b56230184650ea57e5534d5bcfbfc170b97547a1a26f100b5@%3Cdev.mynewt.apache.org%3E

kernel/os/include/os/mynewt.h

@@ -21,6 +21,7 @@
 #define H_OS_MYNEWT_
 
 #include "syscfg/syscfg.h"
+#include "sysdown/sysdown.h"
 #include "sysinit/sysinit.h"
 #include "sysflash/sysflash.h"
 #include "os/os.h"

kernel/os/include/os/os.h

@@ -107,6 +107,17 @@ void os_init(int (*fn)(int argc, char **argv));
  */
 void os_start(void);
 
+/**
+ * Reboots the system.
+ */
+void os_reboot(int reason);
+
+/**
+ * Performs a system reset.  This is typically done at the end of a reboot
+ * procedure.
+ */
+void os_system_reset(void);
+
 #include "os/endian.h"
 #include "os/os_callout.h"
 #include "os/os_cfg.h"

kernel/os/pkg.yml

@@ -24,8 +24,9 @@ pkg.homepage: "http://mynewt.apache.org/"
 pkg.keywords:
 
 pkg.deps:
-    - "@apache-mynewt-core/sys/sysinit"
     - "@apache-mynewt-core/sys/sys"
+    - "@apache-mynewt-core/sys/sysdown"
+    - "@apache-mynewt-core/sys/sysinit"
     - "@apache-mynewt-core/util/mem"
 
 pkg.req_apis:

kernel/os/src/os.c

@@ -24,6 +24,7 @@
 
 #include "hal/hal_os_tick.h"
 #include "hal/hal_bsp.h"
+#include "hal/hal_system.h"
 #include "hal/hal_watchdog.h"
 
 #if MYNEWT_VAL(RTT)
@@ -257,6 +258,23 @@ os_start(void)
 #endif
 }
 
+void
+os_reboot(int reason)
+{
+    sysdown(reason);
+}
+
+void
+os_system_reset(void)
+{
+    /* Tickle watchdog just before re-entering bootloader.  Depending on what
+     * the system has been doing lately, the watchdog timer might be close to
+     * firing.
+     */
+    hal_watchdog_tickle();
+    hal_system_reset();
+}
+
 void
 os_pkg_init(void)
 {

mgmt/newtmgr/nmgr_os/src/newtmgr_os.c

@@ -307,13 +307,7 @@ nmgr_datetime_set(struct mgmt_cbuf *cb)
 static void
 nmgr_reset_tmo(struct os_event *ev)
 {
-    /*
-     * Tickle watchdog just before re-entering bootloader.
-     * Depending on what system has been doing lately, watchdog
-     * timer might be close to firing.
-     */
-    hal_watchdog_tickle();
-    hal_system_reset();
+    os_reboot(HAL_RESET_REQUESTED);
 }
 
 static int

sys/shell/src/shell_os.c

@@ -170,7 +170,8 @@ shell_os_reset_cmd(int argc, char **argv)
     }
 #endif
     os_time_delay(OS_TICKS_PER_SEC / 10);
-    hal_system_reset();
+    os_reboot(HAL_RESET_REQUESTED);
+    return 0;
 }
 
 #if MYNEWT_VAL(SHELL_CMD_HELP)

sys/sysdown/include/sysdown/sysdown.h

@@ -0,0 +1,118 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#ifndef H_SYSDOWN_
+#define H_SYSDOWN_
+
+#include <inttypes.h>
+#include <assert.h>
+#include <stdbool.h>
+#include "syscfg/syscfg.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define SYSDOWN_COMPLETE    0
+#define SYSDOWN_IN_PROGRESS 1
+
+/**
+ * Whether the system is currently shutting down
+ */
+extern bool sysdown_active;
+
+typedef int sysdown_fn(int reason);
+typedef void sysdown_panic_fn(const char *file, int line, const char *func,
+                              const char *expr, const char *msg);
+typedef void sysdown_complete_fn(int status, void *arg);
+
+extern sysdown_fn * const sysdown_cbs[];
+extern sysdown_panic_fn *sysdown_panic_cb;
+
+void sysdown_panic_set(sysdown_panic_fn *panic_fn);
+
+#if MYNEWT_VAL(SYSDOWN_PANIC_MESSAGE)
+
+#if MYNEWT_VAL(SYSDOWN_PANIC_FILE_LINE)
+#define SYSDOWN_PANIC_MSG(msg) sysdown_panic_cb(__FILE__, __LINE__, 0, 0, msg)
+#else
+#define SYSDOWN_PANIC_MSG(msg) sysdown_panic_cb(0, 0, 0, 0, msg)
+#endif
+
+#else
+
+#if MYNEWT_VAL(SYSDOWN_PANIC_FILE_LINE)
+#define SYSDOWN_PANIC_MSG(msg) sysdown_panic_cb(__FILE__, __LINE__, 0, 0, 0)
+#else
+#define SYSDOWN_PANIC_MSG(msg) sysdown_panic_cb(0, 0, 0, 0, 0)
+#endif
+
+#endif
+
+#define SYSDOWN_PANIC() SYSDOWN_PANIC_MSG(NULL)
+
+#define SYSDOWN_ASSERT_MSG(rc, msg) do \
+{                                            \
+    if (!(rc)) {                             \
+        SYSDOWN_PANIC_MSG(msg);              \
+    }                                        \
+} while (0)
+
+#define SYSDOWN_ASSERT(rc) SYSDOWN_ASSERT_MSG(rc, NULL)
+
+/**
+ * Asserts that system shutdown is in progress.  This macro is used to ensure
+ * packages don't get shut down a second time after system shutdown has
+ * completed.
+ */
+#if MYNEWT_VAL(SYSDOWN_CONSTRAIN_DOWN)
+#define SYSDOWN_ASSERT_ACTIVE() assert(sysdown_active)
+#else
+#define SYSDOWN_ASSERT_ACTIVE()
+#endif
+
+/**
+ * @brief Performs a controlled shutdown and reset of the system.
+ *
+ * This function executes each package's shutdown sequence, then triggers a
+ * reboot.
+ *
+ * @param reason                The reason for the shutdown.  One of the
+ *                                  HAL_RESET_[...] codes or an
+ *                                  implementation-defined value.
+ *
+ * @return
+ */
+int sysdown(int reason);
+
+/**
+ * @brief Signals completion of an in-progress sysdown subprocedure.
+ *
+ * If a sysdown subprocedure needs to perform additional work after its
+ * callback finishes, it returns SYSDOWN_IN_PROGRESS.  Later, when the
+ * subprocedure completes, it signals its completion asynchronously with a call
+ * to this function.
+ */
+void sysdown_release(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

sys/sysdown/pkg.yml

@@ -0,0 +1,27 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+pkg.name: sys/sysdown
+pkg.description: Package for kicking off a controlled system shutdown.
+pkg.author: "Apache Mynewt <dev@mynewt.apache.org>"
+pkg.homepage: "http://mynewt.apache.org/"
+pkg.keywords:
+
+pkg.deps:
+    - "@apache-mynewt-core/kernel/os"