+
+/**
+ * Find USB serial devices via the USB vendor ID and product ID.
+ *
+ * @param[in] vendor_id Vendor ID of the USB device.
+ * @param[in] product_id Product ID of the USB device.
+ *
+ * @return A GSList of strings containing the path of the serial device or
+ * NULL if no serial device is found. The returned list must be freed
+ * by the caller.
+ */
+SR_PRIV GSList *sr_serial_find_usb(uint16_t vendor_id, uint16_t product_id)
+{
+#ifdef __linux__
+ const gchar *usb_dev;
+ const char device_tree[] = "/sys/bus/usb/devices/";
+ GDir *devices_dir, *device_dir;
+ GSList *l = NULL;
+ GSList *tty_devs;
+ GSList *matched_paths;
+ FILE *fd;
+ char tmp[5];
+ gchar *vendor_path, *product_path, *path_copy;
+ gchar *prefix, *subdir_path, *device_path, *tty_path;
+ unsigned long read_vendor_id, read_product_id;
+ const char *file;
+
+ l = NULL;
+ tty_devs = NULL;
+ matched_paths = NULL;
+
+ if (!(devices_dir = g_dir_open(device_tree, 0, NULL)))
+ return NULL;
+
+ /*
+ * Find potential candidates using the vendor ID and product ID
+ * and store them in matched_paths.
+ */
+ while ((usb_dev = g_dir_read_name(devices_dir))) {
+ vendor_path = g_strconcat(device_tree,
+ usb_dev, "/idVendor", NULL);
+ product_path = g_strconcat(device_tree,
+ usb_dev, "/idProduct", NULL);
+
+ if (!g_file_test(vendor_path, G_FILE_TEST_EXISTS) ||
+ !g_file_test(product_path, G_FILE_TEST_EXISTS))
+ goto skip_device;
+
+ if ((fd = g_fopen(vendor_path, "r")) == NULL)
+ goto skip_device;
+
+ if (fgets(tmp, sizeof(tmp), fd) == NULL) {
+ fclose(fd);
+ goto skip_device;
+ }
+ read_vendor_id = strtoul(tmp, NULL, 16);
+
+ fclose(fd);
+
+ if ((fd = g_fopen(product_path, "r")) == NULL)
+ goto skip_device;
+
+ if (fgets(tmp, sizeof(tmp), fd) == NULL) {
+ fclose(fd);
+ goto skip_device;
+ }
+ read_product_id = strtoul(tmp, NULL, 16);
+
+ fclose(fd);
+
+ if (vendor_id == read_vendor_id &&
+ product_id == read_product_id) {
+ path_copy = g_strdup(usb_dev);
+ matched_paths = g_slist_prepend(matched_paths,
+ path_copy);
+ }
+
+skip_device:
+ g_free(vendor_path);
+ g_free(product_path);
+ }
+ g_dir_close(devices_dir);
+
+ /* For every matched device try to find a ttyUSBX subfolder. */
+ for (l = matched_paths; l; l = l->next) {
+ subdir_path = NULL;
+
+ device_path = g_strconcat(device_tree, l->data, NULL);
+
+ if (!(device_dir = g_dir_open(device_path, 0, NULL))) {
+ g_free(device_path);
+ continue;
+ }
+
+ prefix = g_strconcat(l->data, ":", NULL);
+
+ while ((file = g_dir_read_name(device_dir))) {
+ if (g_str_has_prefix(file, prefix)) {
+ subdir_path = g_strconcat(device_path,
+ "/", file, NULL);
+ break;
+ }
+ }
+ g_dir_close(device_dir);
+
+ g_free(prefix);
+ g_free(device_path);
+
+ if (subdir_path) {
+ if (!(device_dir = g_dir_open(subdir_path, 0, NULL))) {
+ g_free(subdir_path);
+ continue;
+ }
+ g_free(subdir_path);
+
+ while ((file = g_dir_read_name(device_dir))) {
+ if (g_str_has_prefix(file, "ttyUSB")) {
+ tty_path = g_strconcat("/dev/",
+ file, NULL);
+ sr_dbg("Found USB device %04x:%04x attached to %s.",
+ vendor_id, product_id, tty_path);
+ tty_devs = g_slist_prepend(tty_devs,
+ tty_path);
+ break;
+ }
+ }
+ g_dir_close(device_dir);
+ }
+ }
+ g_slist_free_full(matched_paths, g_free);
+
+ return tty_devs;
+#else
+ (void)vendor_id;
+ (void)product_id;
+
+ return NULL;
+#endif
+}