Detach kernel drivers before changing configurations

This is especially useful when bConfigurationValue is 2, which tends to
be a mixed HID/USB-Audio configuration that the kernel likes to use.
Otherwise usbmuxd cannot change the configuration.

1 files changed, 20 insertions, 0 deletions

diff --git a/daemon/usb-linux.c b/daemon/usb-linux.c
index cc1bbaf..c9420c8 100644
--- a/daemon/usb-linux.c
+++ b/daemon/usb-linux.c
@@ -286,6 +286,26 @@ int usb_discover(void)
                         continue;
                 }
                 if (current_config != devdesc.bNumConfigurations) {
+                        struct libusb_config_descriptor *config;
+                        if((res = libusb_get_active_config_descriptor(dev, &config)) != 0) {
+                                usbmuxd_log(LL_NOTICE, "Could not get old configuration descriptor for device %d-%d: %d", bus, address, res);
+                        } else {
+                                for(j=0; j<config->bNumInterfaces; j++) {
+                                        const struct libusb_interface_descriptor *intf = &config->interface[j].altsetting[0];
+                                        if((res = libusb_kernel_driver_active(handle, intf->bInterfaceNumber)) < 0) {
+                                                usbmuxd_log(LL_NOTICE, "Could not check kernel ownership of interface %d for device %d-%d: %d", intf->bInterfaceNumber, bus, address, res);
+                                                continue;
+                                        }
+                                        if(res == 1) {
+                                                usbmuxd_log(LL_INFO, "Detaching kernel driver for device %d-%d, interface %d", bus, address, intf->bInterfaceNumber);
+                                                if((res = libusb_detach_kernel_driver(handle, intf->bInterfaceNumber)) < 0) {
+                                                        usbmuxd_log(LL_WARNING, "Could not detach kernel driver (%d), configuration change will probably fail!", res);
+                                                        continue;
+                                                }
+                                        }
+                                }
+                                libusb_free_config_descriptor(config);
+                        }
                         if((res = libusb_set_configuration(handle, devdesc.bNumConfigurations)) != 0) {
                                 usbmuxd_log(LL_WARNING, "Could not set configuration %d for device %d-%d: %d", devdesc.bNumConfigurations, bus, address, res);
                                 libusb_close(handle);