+static int open_device(am7xxx_context *ctx,
+ unsigned int device_index,
+ libusb_device *usb_dev,
+ am7xxx_device **dev)
+{
+ int ret;
+ int current_configuration;
+
+ *dev = find_device(ctx, device_index);
+ if (*dev == NULL) {
+ ret = -ENODEV;
+ goto out;
+ }
+
+ /* the usb device has already been opened */
+ if ((*dev)->usb_device) {
+ debug(ctx, "(*dev)->usb_device already set\n");
+ ret = 1;
+ goto out;
+ }
+
+ ret = libusb_open(usb_dev, &((*dev)->usb_device));
+ if (ret < 0) {
+ debug(ctx, "libusb_open failed: %s\n", libusb_error_name(ret));
+ goto out;
+ }
+
+ /* XXX, the device is now open, if any of the calls below fail we need
+ * to close it again before bailing out.
+ */
+
+ current_configuration = -1;
+ libusb_get_configuration((*dev)->usb_device, ¤t_configuration);
+ if (current_configuration != (*dev)->desc->configuration) {
+ /*
+ * In principle kernel drivers bound to each interface should
+ * be detached before setting the configuration, but in
+ * practice this is not necessary for most devices.
+ *
+ * For example something like the following function would be
+ * called:
+ * libusb_detach_all_kernel_drivers((*dev)->usb_device);
+ */
+ ret = libusb_set_configuration((*dev)->usb_device,
+ (*dev)->desc->configuration);
+ if (ret < 0) {
+ debug(ctx, "libusb_set_configuration failed: %s\n",
+ libusb_error_name(ret));
+ debug(ctx, "Cannot set configuration %hhu\n",
+ (*dev)->desc->configuration);
+ goto out_libusb_close;
+ }
+ }
+
+ libusb_set_auto_detach_kernel_driver((*dev)->usb_device, 1);
+
+ ret = libusb_claim_interface((*dev)->usb_device,
+ (*dev)->desc->interface_number);
+ if (ret < 0) {
+ debug(ctx, "libusb_claim_interface failed: %s\n",
+ libusb_error_name(ret));
+ debug(ctx, "Cannot claim interface %hhu\n",
+ (*dev)->desc->interface_number);
+ 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, ¤t_configuration);
+ if (current_configuration != (*dev)->desc->configuration) {
+ debug(ctx, "libusb configuration changed (expected: %hhu, current: %hhu\n",
+ (*dev)->desc->configuration, current_configuration);
+ ret = -EINVAL;
+ goto out_libusb_close;
+ }
+out:
+ return ret;
+
+out_libusb_close:
+ libusb_close((*dev)->usb_device);
+ (*dev)->usb_device = NULL;
+ return ret;
+}
+