What is _UID?
Quick note explaining _UID for BIOS/UEFI and embedded firmware readers.
What is _UID?
_UID is an ACPI object used to distinguish multiple devices that share the same _HID.
Why it matters
- Helps the OS understand platform devices or resources.
- Connects firmware description with OS driver behavior.
- Useful when debugging ACPI namespace, resource, or table issues.
Practical example
Example: if the OS does not bind a driver to an ACPI device, check _STA, _HID/_CID, and _CRS in that order.
Quick checklist
- Does the object/table appear in the ACPI namespace or OS table dump?
- Do _STA, _HID/_CID, and _CRS report consistent information?
- Do OS logs show ACPI errors or resource conflicts?
Quick takeaway
_UID is the contract between firmware description and OS interpretation.
Related notes
Public references
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