X-Git-Url: https://git.ao2.it/libam7xxx.git/blobdiff_plain/ed6e13d9ce88f2cc1decf9a1defe381613274d27..313d4a702aefeac3c8360141ae9037a8fdd47746:/src/am7xxx.c

diff --git a/src/am7xxx.c b/src/am7xxx.c
index 006b216..321a193 100644
--- a/src/am7xxx.c
+++ b/src/am7xxx.c
@@ -708,6 +708,7 @@ static int open_device(am7xxx_context *ctx,
 		       am7xxx_device **dev)
 {
 	int ret;
+	int current_configuration;
 
 	*dev = find_device(ctx, device_index);
 	if (*dev == NULL) {
@@ -732,13 +733,17 @@ static int open_device(am7xxx_context *ctx,
 	 * to close it again before bailing out.
 	 */
 
-	ret = libusb_set_configuration((*dev)->usb_device,
-				       (*dev)->desc->configuration);
-	if (ret < 0) {
-		debug(ctx, "libusb_set_configuration failed\n");
-		debug(ctx, "Cannot set configuration %hhu\n",
-		      (*dev)->desc->configuration);
-		goto out_libusb_close;
+	current_configuration = -1;
+	libusb_get_configuration((*dev)->usb_device, &current_configuration);
+	if (current_configuration != (*dev)->desc->configuration) {
+		ret = libusb_set_configuration((*dev)->usb_device,
+					       (*dev)->desc->configuration);
+		if (ret < 0) {
+			debug(ctx, "libusb_set_configuration failed\n");
+			debug(ctx, "Cannot set configuration %hhu\n",
+			      (*dev)->desc->configuration);
+			goto out_libusb_close;
+		}
 	}
 
 	ret = libusb_claim_interface((*dev)->usb_device,
@@ -747,12 +752,27 @@ static int open_device(am7xxx_context *ctx,
 		debug(ctx, "libusb_claim_interface failed\n");
 		debug(ctx, "Cannot claim interface %hhu\n",
 		      (*dev)->desc->interface_number);
-out_libusb_close:
-		libusb_close((*dev)->usb_device);
-		(*dev)->usb_device = NULL;
+		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;
+	libusb_get_configuration((*dev)->usb_device, &current_configuration);
+	if (current_configuration != (*dev)->desc->configuration) {
+		debug(ctx, "libusb configuration changed\n");
+		debug(ctx, "Cannot claim interface %hhu\n",
+		      (*dev)->desc->interface_number);
+		goto out_libusb_close;
 	}
 out:
 	return ret;
+
+out_libusb_close:
+	libusb_close((*dev)->usb_device);
+	(*dev)->usb_device = NULL;
+	return ret;
 }
 
 typedef enum {
@@ -764,13 +784,14 @@ typedef enum {
  * This is where the central logic of multi-device support is.
  *
  * When 'op' == SCAN_OP_BUILD_DEVLIST the parameters 'open_device_index' and
- * 'dev' are ignored; the function returns 0 on success and a negative value
+ * 'dev' are ignored; the function returns 0 on success or a negative value
  * on error.
  *
  * When 'op' == SCAN_OP_OPEN_DEVICE the function opens the supported USB
  * device with index 'open_device_index' and returns the correspondent
- * am7xxx_device in the 'dev' parameter; the function returns 0 on success,
- * 1 if the device was already open and a negative value on error.
+ * am7xxx_device in the 'dev' parameter; the function returns the value from
+ * open_device(), which is 0 on success, 1 if the device was already open or
+ * a negative value on error.
  *
  * NOTES:
  * if scan_devices() fails when called with 'op' == SCAN_OP_BUILD_DEVLIST,
@@ -837,11 +858,12 @@ static int scan_devices(am7xxx_context *ctx, scan_op op,
 							  open_device_index,
 							  list[i],
 							  dev);
-					if (ret < 0) {
+					if (ret < 0)
 						debug(ctx, "open_device failed\n");
-						goto out;
-					}
 
+					/* exit the loop unconditionally after
+					 * attempting to open the device
+					 * requested by the user */
 					goto out;
 				}
 				current_index++;