monitor: Add support for reading over J-Link RTT

This patch adds support for reading data over J-Link RTT. It can be
used as replacement for TTY when reading from embedded devices since
it's much faster and does block a UART. Data format is the same as
for TTY. At the moment monitor over RTT is only supported by Apache
Mynewt project.

Reading data is done by polling RTT every 1 msec since there is no
blocking API to read something from RTT buffer.

To enable reading from RTT, J-Link configuration needs to be passed via
command line (all parameters except <device> can be skipped to use
default value):
  -J <device>,<serialno=0>,<interface=swd>,<speed=1000>
  -J nrf52,683649029

In some cases J-Link cannot locate RTT buffer in RAM. In such case
RAM area and buffer name should be provided via command line:
  -R <address=0x0>,<area=0x1000>,<buffer=monitor>
  -R 0x20000000,0x10000

4 files changed, 72 insertions, 3 deletions

diff --git a/Makefile.tools b/Makefile.tools
index 81ed2e30d..7ce05b7ef 100644
--- a/Makefile.tools
+++ b/Makefile.tools
@@ -42,9 +42,10 @@ monitor_btmon_SOURCES = monitor/main.c monitor/bt.h \
 				monitor/analyze.h monitor/analyze.c \
 				monitor/intel.h monitor/intel.c \
 				monitor/broadcom.h monitor/broadcom.c \
+				monitor/jlink.h monitor/jlink.c \
 				monitor/tty.h
 monitor_btmon_LDADD = lib/libbluetooth-internal.la \
-				src/libshared-mainloop.la $(UDEV_LIBS)
+				src/libshared-mainloop.la $(UDEV_LIBS) -ldl
 endif
 
 if LOGGER
diff --git a/monitor/control.c b/monitor/control.c
index 4022e7644..1e9054db3 100644
--- a/monitor/control.c
+++ b/monitor/control.c
@@ -57,6 +57,7 @@
 #include "ellisys.h"
 #include "tty.h"
 #include "control.h"
+#include "jlink.h"
 
 static struct btsnoop *btsnoop_file = NULL;
 static bool hcidump_fallback = false;
@@ -1416,6 +1417,55 @@ int control_tty(const char *path, unsigned int speed)
 	return 0;
 }
 
+static void rtt_callback(int id, void *user_data)
+{
+	struct control_data *data = user_data;
+	ssize_t len;
+
+	do {
+		len = jlink_rtt_read(data->buf + data->offset,
+					sizeof(data->buf) - data->offset);
+		data->offset += len;
+		process_data(data);
+	} while (len > 0);
+
+	if (mainloop_modify_timeout(id, 1) < 0)
+		mainloop_exit_failure();
+}
+
+int control_rtt(char *jlink, char *rtt)
+{
+	struct control_data *data;
+
+	if (jlink_init() < 0) {
+		fprintf(stderr, "Failed to initialize J-Link library\n");
+		return -EIO;
+	}
+
+	if (jlink_connect(jlink) < 0) {
+		fprintf(stderr, "Failed to connect to target device\n");
+		return -ENODEV;
+	}
+
+	if (jlink_start_rtt(rtt) < 0) {
+		fprintf(stderr, "Failed to initialize RTT\n");
+		return -ENODEV;
+	}
+
+	printf("--- RTT opened ---\n");
+
+	data = new0(struct control_data, 1);
+	data->channel = HCI_CHANNEL_MONITOR;
+	data->fd = -1;
+
+	if (mainloop_add_timeout(1, rtt_callback, data, free_data) < 0) {
+		free(data);
+		return -EIO;
+	}
+
+	return 0;
+}
+
 bool control_writer(const char *path)
 {
 	btsnoop_file = btsnoop_create(path, 0, 0, BTSNOOP_FORMAT_MONITOR);
diff --git a/monitor/control.h b/monitor/control.h
index a9691e32f..ddf485f1f 100644
--- a/monitor/control.h
+++ b/monitor/control.h
@@ -28,6 +28,7 @@ bool control_writer(const char *path);
 void control_reader(const char *path, bool pager);
 void control_server(const char *path);
 int control_tty(const char *path, unsigned int speed);
+int control_rtt(char *jlink, char *rtt);
 int control_tracing(void);
 void control_disable_decoding(void);
 void control_filter_index(uint16_t index);
diff --git a/monitor/main.c b/monitor/main.c
index acd44a098..479df859c 100644
--- a/monitor/main.c
+++ b/monitor/main.c
@@ -75,6 +75,10 @@ static void usage(void)
 		"\t-A, --a2dp             Dump A2DP stream traffic\n"
 		"\t-E, --ellisys [ip]     Send Ellisys HCI Injection\n"
 		"\t-P, --no-pager         Disable pager usage\n"
+		"\t-J  --jlink <device>,[<serialno>],[<interface>],[<speed>]\n"
+		"\t                       Read data from RTT\n"
+		"\t-R  --rtt [<address>],[<area>],[<name>]\n"
+		"\t                       RTT control block parameters\n"
 		"\t-h, --help             Show help options\n");
 }
 
@@ -94,6 +98,8 @@ static const struct option main_options[] = {
 	{ "a2dp",      no_argument,       NULL, 'A' },
 	{ "ellisys",   required_argument, NULL, 'E' },
 	{ "no-pager",  no_argument,       NULL, 'P' },
+	{ "jlink",     required_argument, NULL, 'J' },
+	{ "rtt",       required_argument, NULL, 'R' },
 	{ "todo",      no_argument,       NULL, '#' },
 	{ "version",   no_argument,       NULL, 'v' },
 	{ "help",      no_argument,       NULL, 'h' },
@@ -112,6 +118,8 @@ int main(int argc, char *argv[])
 	unsigned int tty_speed = B115200;
 	unsigned short ellisys_port = 0;
 	const char *str;
+	char *jlink = NULL;
+	char *rtt = NULL;
 	int exit_status;
 
 	mainloop_init();
@@ -122,7 +130,7 @@ int main(int argc, char *argv[])
 		int opt;
 		struct sockaddr_un addr;
 
-		opt = getopt_long(argc, argv, "r:w:a:s:p:i:d:B:V:tTSAEPvh",
+		opt = getopt_long(argc, argv, "r:w:a:s:p:i:d:B:V:tTSAE:PJ:R:vh",
 							main_options, NULL);
 		if (opt < 0)
 			break;
@@ -194,6 +202,12 @@ int main(int argc, char *argv[])
 		case 'P':
 			use_pager = false;
 			break;
+		case 'J':
+			jlink = optarg;
+			break;
+		case 'R':
+			rtt = optarg;
+			break;
 		case '#':
 			packet_todo();
 			lmp_todo();
@@ -246,12 +260,15 @@ int main(int argc, char *argv[])
 	if (ellisys_server)
 		ellisys_enable(ellisys_server, ellisys_port);
 
-	if (!tty && control_tracing() < 0)
+	if (!tty && !jlink && control_tracing() < 0)
 		return EXIT_FAILURE;
 
 	if (tty && control_tty(tty, tty_speed) < 0)
 		return EXIT_FAILURE;
 
+	if (jlink && control_rtt(jlink, rtt) < 0)
+		return EXIT_FAILURE;
+
 	exit_status = mainloop_run_with_signal(signal_callback, NULL);
 
 	keys_cleanup();