What is Vendor ID and Device ID?
Quick note explaining Vendor ID and Device ID for BIOS/UEFI and embedded firmware readers.
Vendor ID and Device ID is a PCI/PCIe firmware concept used during device discovery, configuration-space access, resource allocation, or driver binding.
Why it matters
- Explains how firmware discovers and configures PCI/PCIe devices.
- Helps debug missing devices, invalid BARs, and resource-allocation issues.
- Connects PCI configuration space with UEFI driver binding.
Practical example
Example: if Vendor ID reads as 0xFFFF, firmware may not be seeing the device on the bus, or the bus/device/function address may be wrong.
Quick checklist
Quick takeaway
Vendor ID and Device ID is best debugged by connecting configuration-space data with UEFI handle/protocol state.
How I usually read it
I try not to treat Vendor ID and Device ID as a dictionary entry. I read it as part of a firmware path: who produces it, who consumes it, and what symptom appears when it is wrong. That habit makes the note useful during debugging, not only during study.
Where it shows up
For example, when an OS cannot see a device, the driver is not always the first suspect. I would compare the firmware description with the OS view: IDs, resources, table contents, and logs. Vendor ID and Device ID is one piece of that platform description chain.
In a real debugging session
Connect Vendor ID and Device ID to enumeration: BDF discovery, Vendor ID/Device ID, class code, BAR sizing, resource allocation, and driver binding. If a device disappears, the issue may be enumeration or resource assignment rather than the driver itself.
Common clues include Vendor ID reading as 0xFFFF, suspicious BAR sizes, or a stale device path after moving hardware.
Related notes
- What is BDF in PCIe?
- What is BAR in PCIe?
- What is PCI Configuration Space?
- What is PCI Root Bridge?
- What is PCI Resource Allocation?
Public references
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