# Configuration Data Offsets Constants for the offsets that you use to read and write configuration registers. ## Topics ### Offsets [`kIOPCIConfigurationOffsetVendorID`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetVendorID) The offset to the 16-bit value that identifies the manufacturer of the device. [`kIOPCIConfigurationOffsetDeviceID`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetDeviceID) The offset to the 16-bit value that the manufacturer uses to identify the particular function. [`kIOPCIConfigurationOffsetCommand`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetCommand) The offset to the 16-bit value that defines how the device responds to commands. [`kIOPCIConfigurationOffsetStatus`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetStatus) The offset to the 16-bit value that contains the status of the device. [`kIOPCIConfigurationOffsetRevisionID`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetRevisionID) The offset to the 8-bit value that the manufacturer uses to identify the revision of the device. [`kIOPCIConfigurationOffsetClassCode`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetClassCode) The offset to the 24-bit, read-only value that identifies the generic operation of the device. [`kIOPCIConfigurationOffsetCacheLineSize`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetCacheLineSize) The offset to the 8-bit value that contains legacy information about the cache line size. [`kIOPCIConfigurationOffsetLatencyTimer`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetLatencyTimer) The offset to the 8-bit value that containsn legacy information for devices with a primary latency timer. [`kIOPCIConfigurationOffsetHeaderType`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetHeaderType) The offset to the 8-bit value that defines the layout of the second part of the predefined header. [`kIOPCIConfigurationOffsetBIST`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetBIST) The offset to the 8-bit value that controls and reports the status of the device’s built-in, self-test behavior. [`kIOPCIConfigurationOffsetBaseAddress0`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetBaseAddress0) The offset to the 32-bit value for base address 0. [`kIOPCIConfigurationOffsetBaseAddress1`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetBaseAddress1) The offset to the 32-bit value for base address 1. [`kIOPCIConfigurationOffsetBaseAddress2`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetBaseAddress2) The offset to the 32-bit value for base address 2. [`kIOPCIConfigurationOffsetBaseAddress3`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetBaseAddress3) The offset to the 32-bit value for base address 3. [`kIOPCIConfigurationOffsetBaseAddress4`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetBaseAddress4) The offset to the 32-bit value for base address 4. [`kIOPCIConfigurationOffsetBaseAddress5`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetBaseAddress5) The offset to the 32-bit value for base address 5. [`kIOPCIConfigurationOffsetCardBusCISPtr`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetCardBusCISPtr) The offset to the 32-bit read-only value that describes legacy PCI functionality. [`kIOPCIConfigurationOffsetSubSystemVendorID`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetSubSystemVendorID) The offset to the 16-bit value that identifies the manufacturer of a device containing common PCI components. [`kIOPCIConfigurationOffsetSubSystemID`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetSubSystemID) The offset to the 16-bit value that identifies a specific device that uses common PCI components. [`kIOPCIConfigurationOffsetExpansionROMBase`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetExpansionROMBase) The offset to the 32-bit value that contains the base address and size of the device’s expansion ROM. [`kIOPCIConfigurationOffsetCapabilitiesPtr`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetCapabilitiesPtr) The offset to the 8-bit value that points to the linked list of capabilities the device implements. [`kIOPCIConfigurationOffsetInterruptLine`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetInterruptLine) The offset to the 8-bit value that contains interrupt line-routing information. [`kIOPCIConfigurationOffsetInterruptPin`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetInterruptPin) The offset to the 8-bit read-only value that identifies the device’s supported interrupt messages. [`kIOPCIConfigurationOffsetMinimumGrant`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetMinimumGrant) The offset to the 8-bit value that contains legacy PCI information about the minimum grant. [`kIOPCIConfigurationOffsetMaximumLatency`](/documentation/PCIDriverKit/kIOPCIConfigurationOffsetMaximumLatency) The offset to the 8-bit value that contains legacy PCI information about the maximum latency. --- 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)