nshterm: start a nsh console on any device

this is used in APM startup to fallback to a console on ttyACM0 if
startup fails for any reason

src/systemcmds/nshterm/module.mk

@@ -0,0 +1,41 @@
+############################################################################
+#
+#   Copyright (c) 2012, 2013 PX4 Development Team. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name PX4 nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################################
+
+#
+# Build nshterm utility
+#
+
+MODULE_COMMAND	 = nshterm
+SRCS		 = nshterm.c
+
+MODULE_STACKSIZE = 3000

src/systemcmds/nshterm/nshterm.c

@@ -0,0 +1,90 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2012, 2013 PX4 Development Team. All rights reserved.
+ *   Author: Andrew Tridgell
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file nshterm.c
+ * start a nsh terminal on a given port. This can be useful for error
+ * handling in startup scripts to start a nsh shell on /dev/ttyACM0
+ * for diagnostics
+ */
+
+#include <nuttx/config.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <apps/nsh.h>
+#include <fcntl.h>
+
+__EXPORT int nshterm_main(int argc, char *argv[]);
+
+int
+nshterm_main(int argc, char *argv[])
+{
+    if (argc < 2) {
+        printf("Usage: nshterm <device>\n");
+        exit(1);
+    }
+    uint8_t retries = 0;
+    int fd = -1;
+    while (retries < 5) {
+        // the retries are to cope with the behaviour of /dev/ttyACM0
+        // which may not be ready immediately.
+        fd = open(argv[1], O_RDWR);
+        if (fd != -1) {
+            break;
+        }
+        usleep(100000);
+        retries++;
+    }
+    if (fd == -1) {
+        perror(argv[1]);
+        exit(1);
+    }
+    // setup standard file descriptors
+    close(0);
+    close(1);
+    close(2);
+    dup2(fd, 0);
+    dup2(fd, 1);
+    dup2(fd, 2);
+
+    nsh_consolemain(0, NULL);
+
+    close(fd);
+
+    return OK;
+}