host: Allow matching of device to USB path, not just address

USB addresses change every time the device re-enumerates, while the path
reflects the physical topology of USB connections and stays persistent
unless the usb cabling is changed.  Let's allow the user to specify the
path instead of the address to uniquely identify a given slot.

host/libusb_util.c

@@ -3,11 +3,33 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
+#include <string.h>
 
 #include <libusb.h>
 
 #include "libusb_util.h"
 
+static char path_buf[USB_MAX_PATH_LEN];
+
+static char *get_path(libusb_device *dev)
+{
+#if (defined(LIBUSB_API_VERSION) && LIBUSB_API_VERSION >= 0x01000102) || (defined(LIBUSBX_API_VERSION) && LIBUSBX_API_VERSION >= 0x01000102)
+	uint8_t path[8];
+	int r,j;
+	r = libusb_get_port_numbers(dev, path, sizeof(path));
+	if (r > 0) {
+		sprintf(path_buf,"%d-%d",libusb_get_bus_number(dev),path[0]);
+		for (j = 1; j < r; j++){
+			sprintf(path_buf+strlen(path_buf),".%d",path[j]);
+		};
+	}
+	return path_buf;
+#else
+# warning "libusb too old - building without USB path support!"
+	return NULL;
+#endif
+}
+
 static int match_dev_id(const struct libusb_device_descriptor *desc, const struct dev_id *id)
 {
 	if ((desc->idVendor == id->vendor_id) && (desc->idProduct == id->product_id))
@@ -79,6 +101,7 @@ int dev_find_matching_interfaces(libusb_device *dev, int class, int sub_class, i
 	struct libusb_device_descriptor dev_desc;
 	int rc, i, out_idx = 0;
 	uint8_t addr;
+	char *path;
 
 	rc = libusb_get_device_descriptor(dev, &dev_desc);
 	if (rc < 0) {
@@ -87,6 +110,7 @@ int dev_find_matching_interfaces(libusb_device *dev, int class, int sub_class, i
 	}
 
 	addr = libusb_get_device_address(dev);
+	path = get_path(dev);
 
 	/* iterate over all configurations */
 	for (i = 0; i < dev_desc.bNumConfigurations; i++) {
@@ -117,6 +141,8 @@ int dev_find_matching_interfaces(libusb_device *dev, int class, int sub_class, i
 				out[out_idx].vendor = dev_desc.idVendor;
 				out[out_idx].product = dev_desc.idProduct;
 				out[out_idx].addr = addr;
+				strncpy(out[out_idx].path, path, sizeof(out[out_idx].path));
+				out[out_idx].path[sizeof(out[out_idx].path)-1] = '\0';
 				out[out_idx].configuration = conf_desc->bConfigurationValue;
 				out[out_idx].interface = if_desc->bInterfaceNumber;
 				out[out_idx].altsetting = if_desc->bAlternateSetting;
@@ -198,9 +224,12 @@ libusb_device_handle *usb_open_claim_interface(libusb_context *ctx,
 
 	for (dev = list; *dev; dev++) {
 		int addr;
+		char *path;
 
 		addr = libusb_get_device_address(*dev);
-		if (addr == ifm->addr) {
+		path = get_path(*dev);
+		if ((ifm->addr && addr == ifm->addr) ||
+		    (strlen(ifm->path) && !strcmp(path, ifm->path))) {
 			rc = libusb_open(*dev, &usb_devh);
 			if (rc < 0) {
 				perror("Cannot open device");

host/libusb_util.h

@@ -2,6 +2,8 @@
 
 #include <libusb.h>
 
+#define USB_MAX_PATH_LEN 20
+
 struct dev_id {
 	uint16_t vendor_id;
 	uint16_t product_id;
@@ -21,6 +23,8 @@ struct usb_interface_match {
 	uint16_t product;
 	/* USB Bus Address */
 	uint8_t addr;
+	/* physical path */
+	char path[USB_MAX_PATH_LEN];
 	/* configuration of matching interface */
 	uint8_t configuration;
 	/* interface number of matching interface */

host/simtrace2-remsim.c

@@ -522,6 +522,7 @@ static const struct option opts[] = {
 	{ "usb-interface", 1, 0, 'I' },
 	{ "usb-altsetting", 1, 0, 'S' },
 	{ "usb-address", 1, 0, 'A' },
+	{ "usb-path", 1, 0, 'H' },
 	{ NULL, 0, 0, 0 }
 };
 
@@ -601,6 +602,7 @@ int main(int argc, char **argv)
 	int if_num = 0, vendor_id = -1, product_id = -1;
 	int config_id = -1, altsetting = 0, addr = -1;
 	char *remote_udp_host = NULL;
+	char *path = NULL;
 	struct osim_reader_hdl *reader;
 	struct osim_card_hdl *card;
 
@@ -609,7 +611,7 @@ int main(int argc, char **argv)
 	while (1) {
 		int option_index = 0;
 
-		c = getopt_long(argc, argv, "r:p:hi:V:P:C:I:S:A:ak", opts, &option_index);
+		c = getopt_long(argc, argv, "r:p:hi:V:P:C:I:S:A:H:ak", opts, &option_index);
 		if (c == -1)
 			break;
 		switch (c) {
@@ -650,6 +652,9 @@ int main(int argc, char **argv)
 		case 'A':
 			addr = atoi(optarg);
 			break;
+		case 'H':
+			path = optarg;
+			break;
 		}
 	}
 
@@ -714,6 +719,8 @@ int main(int argc, char **argv)
 			ifm->interface = if_num;
 			ifm->altsetting = altsetting;
 			ifm->addr = addr;
+			if (path)
+				osmo_strlcpy(ifm->path, path, sizeof(ifm->path));
 			transp->usb_devh = usb_open_claim_interface(NULL, ifm);
 			if (!transp->usb_devh) {
 				fprintf(stderr, "can't open USB device\n");

host/simtrace2_usb.c

@@ -41,8 +41,8 @@ static int find_devices(void)
 		libusb_device_handle *dev_handle;
 		char strbuf[256];
 
-		printf("\t%04x:%04x Addr=%u, Cfg=%u, Intf=%u, Alt=%u: %d/%d/%d ",
-			m->vendor, m->product, m->addr,
+		printf("\t%04x:%04x Addr=%u, Path=%s, Cfg=%u, Intf=%u, Alt=%u: %d/%d/%d ",
+			m->vendor, m->product, m->addr, m->path,
 			m->configuration, m->interface, m->altsetting,
 			m->class, m->sub_class, m->protocol);