From ba30def0cce654c843873f8653d1f3a5338e8410 Mon Sep 17 00:00:00 2001
From: Antonio Ospite <ao2@ao2.it>
Date: Wed, 10 Jun 2015 11:57:37 +0200
Subject: [PATCH] Set configuration following
 http://libusb.sourceforge.net/api-1.0/caveats.html

---
 src/visomat-data-downloader.c | 37 +++++++++++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/visomat-data-downloader.c b/src/visomat-data-downloader.c
index f93757d..818473f 100644
--- a/src/visomat-data-downloader.c
+++ b/src/visomat-data-downloader.c
@@ -317,6 +317,7 @@ int main(void)
 {
 	int ret;
 	libusb_device_handle *dev;
+	int current_configuration;
 
 	ret = libusb_init(NULL);
 	if (ret < 0) {
@@ -335,15 +336,25 @@ int main(void)
 		goto out_libusb_exit;
 	}
 
-	ret = libusb_set_configuration(dev, VISOMAT_CONFIGURATION);
+	current_configuration = -1;
+	ret = libusb_get_configuration(dev, &current_configuration);
 	if (ret < 0) {
-		fprintf(stderr, "libusb_set_configuration failed: %s\n",
+		fprintf(stderr, "libusb_get_configuration failed: %s\n",
 			libusb_error_name(ret));
-		fprintf(stderr, "Cannot set configuration %hhu\n",
-			VISOMAT_CONFIGURATION);
 		goto out_libusb_close;
 	}
 
+	if (current_configuration != VISOMAT_CONFIGURATION) {
+		ret = libusb_set_configuration(dev, VISOMAT_CONFIGURATION);
+		if (ret < 0) {
+			fprintf(stderr, "libusb_set_configuration failed: %s\n",
+				libusb_error_name(ret));
+			fprintf(stderr, "Cannot set configuration %hhu\n",
+				VISOMAT_CONFIGURATION);
+			goto out_libusb_close;
+		}
+	}
+
 	libusb_set_auto_detach_kernel_driver(dev, 1);
 
 	ret = libusb_claim_interface(dev, VISOMAT_INTERFACE);
@@ -355,6 +366,24 @@ int main(void)
 		goto out_libusb_close;
 	}
 
+	/* Checking that the configuration has not changed, as suggested in
+	 * http://libusb.sourceforge.net/api-1.0/caveats.html
+	 */
+	current_configuration = -1;
+	ret = libusb_get_configuration(dev, &current_configuration);
+	if (ret < 0) {
+		fprintf(stderr, "libusb_get_configuration after claim failed: %s\n",
+			libusb_error_name(ret));
+		goto out_libusb_release_interface;
+	}
+
+	if (current_configuration != VISOMAT_CONFIGURATION) {
+		fprintf(stderr, "libusb configuration changed (expected: %hhu, current: %hhu\n",
+			VISOMAT_CONFIGURATION, current_configuration);
+		ret = -EINVAL;
+		goto out_libusb_release_interface;
+	}
+
 	ret = visomat_get_datetime(dev);
 	if (ret < 0)
 		goto out_libusb_release_interface;
-- 
2.1.4