+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) {
+ 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;
+ ret = libusb_get_configuration((*dev)->usb_device,
+ ¤t_configuration);
+ if (ret < 0) {
+ debug(ctx, "libusb_get_configuration failed: %s\n",
+ libusb_error_name(ret));
+ goto out_libusb_close;
+ }
+
+ if (current_configuration != (*dev)->desc->configuration) {
+ /*
+ * In principle, before setting a new configuration, kernel
+ * drivers should be detached from _all_ interfaces; for
+ * example calling something like the following "invented"
+ * function _before_ setting the new configuration:
+ *
+ * libusb_detach_all_kernel_drivers((*dev)->usb_device);
+ *
+ * However, in practice, this is not necessary for most
+ * devices as they have only one configuration.
+ *
+ * When a device only has one configuration:
+ *
+ * - if there was a kernel driver bound to the device, it
+ * had already set the configuration and the call below
+ * will be skipped;
+ *
+ * - if no kernel driver was bound to the device, the call
+ * below will suceed.
+ */
+ 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;
+ ret = libusb_get_configuration((*dev)->usb_device,
+ ¤t_configuration);
+ if (ret < 0) {
+ debug(ctx, "libusb_get_configuration after claim failed: %s\n",
+ libusb_error_name(ret));
+ goto out_libusb_release_interface;
+ }
+
+ if (current_configuration != (*dev)->desc->configuration) {
+ debug(ctx, "libusb configuration changed (expected: %hhu, current: %d\n",
+ (*dev)->desc->configuration, current_configuration);
+ ret = -EINVAL;
+ goto out_libusb_release_interface;
+ }
+out:
+ return ret;
+
+out_libusb_release_interface:
+ libusb_release_interface((*dev)->usb_device,
+ (*dev)->desc->interface_number);
+out_libusb_close:
+ libusb_close((*dev)->usb_device);
+ (*dev)->usb_device = NULL;
+ return ret;
+}
+