PCIe Config Space

When to use

• Reading or writing PCI/PCIe config space: BARs, MSI/MSI-X capabilities, capability linked lists, class codes, PCIe extended capabilities.
• Probing a device's resources (BAR sizes, MSI-X table location) before writing a driver.
• Debugging why an interrupt, DMA mapping, or device BAR is misconfigured.
• Reviewing LLM-generated PCI code that hardcodes config offsets or skips the capability walk.

When not to use