# Descriptor Utilities Iterate over the descriptors of a USB device and fetch specific values. ## Topics ### Configuration Descriptors [`const IOUSBDescriptorHeader *IOUSBGetNextDescriptor(const IOUSBConfigurationDescriptor *configurationDescriptor, const IOUSBDescriptorHeader *currentDescriptor);`](/documentation/USBDriverKit/IOUSBGetNextDescriptor) Gets the next descriptor in a configuration descriptor. [`const IOUSBDescriptorHeader *IOUSBGetNextDescriptorWithType(const IOUSBConfigurationDescriptor *configurationDescriptor, const IOUSBDescriptorHeader *currentDescriptor, const uint8_t type);`](/documentation/USBDriverKit/IOUSBGetNextDescriptorWithType) Finds the next descriptor matching a given type within a configuration descriptor. [`const IOUSBDescriptorHeader *IOUSBGetNextAssociatedDescriptor(const IOUSBConfigurationDescriptor *configurationDescriptor, const IOUSBDescriptorHeader *parentDescriptor, const IOUSBDescriptorHeader *currentDescriptor);`](/documentation/USBDriverKit/IOUSBGetNextAssociatedDescriptor) Gets the next descriptor in the specified configuration descriptor that belongs to another container descriptor. [`const IOUSBDescriptorHeader *IOUSBGetNextAssociatedDescriptorWithType(const IOUSBConfigurationDescriptor *configurationDescriptor, const IOUSBDescriptorHeader *parentDescriptor, const IOUSBDescriptorHeader *currentDescriptor, const uint8_t type);`](/documentation/USBDriverKit/IOUSBGetNextAssociatedDescriptorWithType) Finds the next descriptor matching a specific type within a configuration descriptor that belongs to another container descriptor. [`uint32_t IOUSBGetConfigurationMaxPowerMilliAmps(uint32_t usbDeviceSpeed, const IOUSBConfigurationDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetConfigurationMaxPowerMilliAmps) Extracts the maximum bus current a configuration descriptor requires. ### Interface Descriptors [`const IOUSBInterfaceDescriptor *IOUSBGetNextInterfaceDescriptor(const IOUSBConfigurationDescriptor *configurationDescriptor, const IOUSBDescriptorHeader *currentDescriptor);`](/documentation/USBDriverKit/IOUSBGetNextInterfaceDescriptor) Finds the next interface descriptor in a configuration descriptor. [`const IOUSBInterfaceAssociationDescriptor *IOUSBGetNextInterfaceAssociationDescriptor(const IOUSBConfigurationDescriptor *configurationDescriptor, const IOUSBDescriptorHeader *currentDescriptor);`](/documentation/USBDriverKit/IOUSBGetNextInterfaceAssociationDescriptor) Finds the next interface association descriptor in a configuration descriptor. ### Endpoint Descriptors [`const IOUSBEndpointDescriptor *IOUSBGetNextEndpointDescriptor(const IOUSBConfigurationDescriptor *configurationDescriptor, const IOUSBInterfaceDescriptor *interfaceDescriptor, const IOUSBDescriptorHeader *currentDescriptor);`](/documentation/USBDriverKit/IOUSBGetNextEndpointDescriptor) Finds the next endpoint descriptor associated with an interface descriptor. [`uint8_t IOUSBGetEndpointAddress(const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointAddress) Extracts the direction and number of an endpoint from an endpoint descriptor. [`uint32_t IOUSBGetEndpointBurstSize(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor, const IOUSBSuperSpeedEndpointCompanionDescriptor *companionDescriptor, const IOUSBSuperSpeedPlusIsochronousEndpointCompanionDescriptor *sspCompanionDescriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointBurstSize) Extracts the burst size from endpoint descriptors. [`uint8_t IOUSBGetEndpointDirection(const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointDirection) Extracts the direction of an endpoint from an endpoint descriptor. [`uint32_t IOUSBGetEndpointIntervalEncodedMicroframes(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointIntervalEncodedMicroframes) Extracts the interval of an endpoint descriptor. [`uint32_t IOUSBGetEndpointIntervalFrames(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointIntervalFrames) Extracts the interval of an endpoint descriptor. [`uint32_t IOUSBGetEndpointIntervalMicroframes(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointIntervalMicroframes) Extracts the interval of an endpoint descriptor. [`uint16_t IOUSBGetEndpointMaxPacketSize(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointMaxPacketSize) Extracts the maximum packet size from an endpoint descriptor. [`uint32_t IOUSBGetEndpointMaxStreams(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor, const IOUSBSuperSpeedEndpointCompanionDescriptor *companionDescriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointMaxStreams) Extracts the number of streams an endpoint supports. [`uint32_t IOUSBGetEndpointMaxStreamsEncoded(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor, const IOUSBSuperSpeedEndpointCompanionDescriptor *companionDescriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointMaxStreamsEncoded) Extracts the number of streams an endpoint supports. [`uint8_t IOUSBGetEndpointMult(uint32_t usbDeviceSpeed, const IOUSBEndpointDescriptor *descriptor, const IOUSBSuperSpeedEndpointCompanionDescriptor *companionDescriptor, const IOUSBSuperSpeedPlusIsochronousEndpointCompanionDescriptor *sspCompanionDescriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointMult) Extracts the mult count from endpoint descriptors. [`uint8_t IOUSBGetEndpointNumber(const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointNumber) Extracts the number of an endpoint from an endpoint descriptor. [`uint8_t IOUSBGetEndpointType(const IOUSBEndpointDescriptor *descriptor);`](/documentation/USBDriverKit/IOUSBGetEndpointType) Extracts the type of an endpoint from an endpoint descriptor. ### BOS Descriptors [`const IOUSBDeviceCapabilityDescriptorHeader *IOUSBGetNextCapabilityDescriptor(const IOUSBBOSDescriptor *bosDescriptor, const IOUSBDeviceCapabilityDescriptorHeader *currentDescriptor);`](/documentation/USBDriverKit/IOUSBGetNextCapabilityDescriptor) Gets the next device capability descriptor in a BOS descriptor. [`const IOUSBDeviceCapabilityDescriptorHeader *IOUSBGetNextCapabilityDescriptorWithType(const IOUSBBOSDescriptor *bosDescriptor, const IOUSBDeviceCapabilityDescriptorHeader *currentDescriptor, const uint8_t type);`](/documentation/USBDriverKit/IOUSBGetNextCapabilityDescriptorWithType) Finds the next descriptor matching a given type within a BOS descriptor. [`const IOUSBDeviceCapabilitySuperSpeedUSB *IOUSBGetSuperSpeedDeviceCapabilityDescriptor(const IOUSBBOSDescriptor *bosDescriptor);`](/documentation/USBDriverKit/IOUSBGetSuperSpeedDeviceCapabilityDescriptor) Finds the first SuperSpeed device capability descriptor in a BOS descriptor. [`const IOUSBDeviceCapabilitySuperSpeedPlusUSB *IOUSBGetSuperSpeedPlusDeviceCapabilityDescriptor(const IOUSBBOSDescriptor *bosDescriptor);`](/documentation/USBDriverKit/IOUSBGetSuperSpeedPlusDeviceCapabilityDescriptor) Finds the first SuperSpeed Plus device capability descriptor in a BOS descriptor. [`const IOUSBDeviceCapabilityUSB2Extension *IOUSBGetUSB20ExtensionDeviceCapabilityDescriptor(const IOUSBBOSDescriptor *bosDescriptor);`](/documentation/USBDriverKit/IOUSBGetUSB20ExtensionDeviceCapabilityDescriptor) Finds the first USB 2.0 extension capability descriptor in a BOS descriptor. [`const IOUSBDeviceCapabilityContainerID *IOUSBGetContainerIDDescriptor(const IOUSBBOSDescriptor *bosDescriptor);`](/documentation/USBDriverKit/IOUSBGetContainerIDDescriptor) Finds the first Container ID capability descriptor in a BOS descriptor. [`const IOUSBPlatformCapabilityDescriptor *IOUSBGetPlatformCapabilityDescriptor(const IOUSBBOSDescriptor *bosDescriptor);`](/documentation/USBDriverKit/IOUSBGetPlatformCapabilityDescriptor) Finds the first platform capability descriptor in a BOS descriptor. [`const IOUSBDeviceCapabilityBillboard *IOUSBGetBillboardDescriptor(const IOUSBBOSDescriptor *bosDescriptor);`](/documentation/USBDriverKit/IOUSBGetBillboardDescriptor) Finds the first billboard capability descriptor in a BOS descriptor. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)