ftdi: allow selecting device by usb bus location

This patch adds a 'ftdi_location' command to select an adapter by usb
bus number and port path.

This is helpful if you have a rack full of adapters in a testing or
manufacturing setup where the only constant is the physical usb bus
location of the adapter you want to address. Vid:Pid are not unique,
serial number _may_ be unique (and maybe not with embedded adapters) but
will change when a new target is plugged.

Specifying a location allows to understand instantly which board failed
bringup or testing.

Change-Id: I403c7c6c8e34fe42041b3f967db80f3160a4f1a3
Signed-off-by: Matthias Welwarsky <matthias.welwarsky@sysgo.com>
Reviewed-on: http://openocd.zylin.com/3351
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>

doc/openocd.texi

@@ -2558,6 +2558,14 @@ If not specified, serial numbers are not considered.
 and are not restricted to containing only decimal digits.)
 @end deffn
 
+@deffn {Config Command} {ftdi_location} <bus>:<port>[,<port>]...
+Specifies the physical USB port of the adapter to use. The path
+roots at @var{bus} and walks down the physical ports, with each
+@var{port} option specifying a deeper level in the bus topology, the last
+@var{port} denoting where the target adapter is actually plugged.
+The USB bus topology can be queried with the command @emph{lsusb -t}.
+@end deffn
+
 @deffn {Config Command} {ftdi_channel} channel
 Selects the channel of the FTDI device to use for MPSSE operations. Most
 adapters use the default, channel 0, but there are exceptions.

src/jtag/drivers/ftdi.c

@@ -91,6 +91,7 @@
 
 static char *ftdi_device_desc;
 static char *ftdi_serial;
+static char *ftdi_location;
 static uint8_t ftdi_channel;
 static uint8_t ftdi_jtag_mode = JTAG_MODE;
 
@@ -631,7 +632,7 @@ static int ftdi_initialize(void)
 
 	for (int i = 0; ftdi_vid[i] || ftdi_pid[i]; i++) {
 		mpsse_ctx = mpsse_open(&ftdi_vid[i], &ftdi_pid[i], ftdi_device_desc,
-				ftdi_serial, ftdi_channel);
+				ftdi_serial, ftdi_location, ftdi_channel);
 		if (mpsse_ctx)
 			break;
 	}
@@ -698,6 +699,19 @@ COMMAND_HANDLER(ftdi_handle_serial_command)
 	return ERROR_OK;
 }
 
+COMMAND_HANDLER(ftdi_handle_location_command)
+{
+	if (CMD_ARGC == 1) {
+		if (ftdi_location)
+			free(ftdi_location);
+		ftdi_location = strdup(CMD_ARGV[0]);
+	} else {
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+
+	return ERROR_OK;
+}
+
 COMMAND_HANDLER(ftdi_handle_channel_command)
 {
 	if (CMD_ARGC == 1)
@@ -875,6 +889,13 @@ static const struct command_registration ftdi_command_handlers[] = {
 		.help = "set the serial number of the FTDI device",
 		.usage = "serial_string",
 	},
+	{
+		.name = "ftdi_location",
+		.handler = &ftdi_handle_location_command,
+		.mode = COMMAND_CONFIG,
+		.help = "set the USB bus location of the FTDI device",
+		.usage = "<bus>:port[,port]...",
+	},
 	{
 		.name = "ftdi_channel",
 		.handler = &ftdi_handle_channel_command,

src/jtag/drivers/mpsse.c

@@ -104,12 +104,65 @@ static bool string_descriptor_equal(libusb_device_handle *device, uint8_t str_in
 	return strncmp(string, desc_string, sizeof(desc_string)) == 0;
 }
 
+static bool device_location_equal(libusb_device *device, const char *location)
+{
+	char *loc = strdup(location);
+	uint8_t port_path[7];
+	int path_step, path_len;
+	uint8_t dev_bus = libusb_get_bus_number(device);
+	char *ptr;
+	bool result = false;
+
+	path_len = libusb_get_port_numbers(device, port_path, 7);
+	if (path_len == LIBUSB_ERROR_OVERFLOW) {
+		LOG_ERROR("cannot determine path to usb device! (more than 7 ports in path)");
+		goto done;
+	}
+
+	LOG_DEBUG("device path has %i steps", path_len);
+
+	ptr = strtok(loc, ":");
+	if (ptr == NULL) {
+		LOG_DEBUG("no ':' in path");
+		goto done;
+	}
+	if (atoi(ptr) != dev_bus) {
+		LOG_DEBUG("bus mismatch");
+		goto done;
+	}
+
+	path_step = 0;
+	while (path_step < 7) {
+		ptr = strtok(NULL, ",");
+		if (ptr == NULL) {
+			LOG_DEBUG("no more tokens in path at step %i", path_step);
+			break;
+		}
+
+		if (path_step < path_len
+			&& atoi(ptr) != port_path[path_step]) {
+			LOG_DEBUG("path mismatch at step %i", path_step);
+			break;
+		}
+
+		path_step++;
+	};
+
+	/* walked the full path, all elements match */
+	if (path_step == path_len)
+		result = true;
+
+ done:
+	free(loc);
+	return result;
+}
+
 /* Helper to open a libusb device that matches vid, pid, product string and/or serial string.
  * Set any field to 0 as a wildcard. If the device is found true is returned, with ctx containing
  * the already opened handle. ctx->interface must be set to the desired interface (channel) number
  * prior to calling this function. */
 static bool open_matching_device(struct mpsse_ctx *ctx, const uint16_t *vid, const uint16_t *pid,
-	const char *product, const char *serial)
+	const char *product, const char *serial, const char *location)
 {
 	libusb_device **list;
 	struct libusb_device_descriptor desc;
@@ -141,6 +194,11 @@ static bool open_matching_device(struct mpsse_ctx *ctx, const uint16_t *vid, con
 			continue;
 		}
 
+		if (location && !device_location_equal(device, location)) {
+			libusb_close(ctx->usb_dev);
+			continue;
+		}
+
 		if (product && !string_descriptor_equal(ctx->usb_dev, desc.iProduct, product)) {
 			libusb_close(ctx->usb_dev);
 			continue;
@@ -263,7 +321,7 @@ error:
 }
 
 struct mpsse_ctx *mpsse_open(const uint16_t *vid, const uint16_t *pid, const char *description,
-	const char *serial, int channel)
+	const char *serial, const char *location, int channel)
 {
 	struct mpsse_ctx *ctx = calloc(1, sizeof(*ctx));
 	int err;
@@ -292,16 +350,17 @@ struct mpsse_ctx *mpsse_open(const uint16_t *vid, const uint16_t *pid, const cha
 		goto error;
 	}
 
-	if (!open_matching_device(ctx, vid, pid, description, serial)) {
+	if (!open_matching_device(ctx, vid, pid, description, serial, location)) {
 		/* Four hex digits plus terminating zero each */
 		char vidstr[5];
 		char pidstr[5];
-		LOG_ERROR("unable to open ftdi device with vid %s, pid %s, description '%s' and "
+		LOG_ERROR("unable to open ftdi device with vid %s, pid %s, description '%s', "
-				"serial '%s'",
+				"serial '%s' at bus location '%s'",
 				vid ? sprintf(vidstr, "%04x", *vid), vidstr : "*",
 				pid ? sprintf(pidstr, "%04x", *pid), pidstr : "*",
 				description ? description : "*",
-				serial ? serial : "*");
+				serial ? serial : "*",
+				location ? location : "*");
 		ctx->usb_dev = 0;
 		goto error;
 	}

src/jtag/drivers/mpsse.h

@@ -43,7 +43,7 @@ struct mpsse_ctx;
 
 /* Device handling */
 struct mpsse_ctx *mpsse_open(const uint16_t *vid, const uint16_t *pid, const char *description,
-	const char *serial, int channel);
+	const char *serial, const char *location, int channel);
 void mpsse_close(struct mpsse_ctx *ctx);
 bool mpsse_is_high_speed(struct mpsse_ctx *ctx);