---
title: "rsdp.h"
summary: "The infrastructure to parse the _Root System Description Pointer_ Table"
---

OSDev Wiki: [RSDP](https://wiki.osdev.org/RSDP)

# `rsdp_descriptor_v1_T` - struct [packed]
The RSDP Table used in ACPI v1.0

| Name         | Type     | Description                                               |
|--------------|----------|-----------------------------------------------------------|
| signature    | char[8]  | Needs to be `"RSD PTR "` (with the withespace at the end) |
| checksum     | uint8_t  | Used to validate the table                                |
| oem_id       | char[6]  | This string identifies the OEM                            |
| revision     | uint8_t  | Tells whether the RSDP is version 1 or 2+                 |
| rsdt_address | uint32_t | The Physical Address of the RSDT                          |

# `rsdp_descriptor_v2_T` - struct [packed]
The RSDP Table used in ACPI v2.0 or higher

| Name              | Type                                                                                                                                | Description                                                                      |
|-------------------|-------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------|
| descriptor_v1     | [rsdp_descriptor_v1_T](https://nerdcult.net/projects/noxos/docs/codebase/drivers/acpi/rsdp.h/#rsdp_descriptor_v1_t---struct-packed) | A table in the format of the ACPI 1.0 specification                              |
| length            | uint32_t                                                                                                                            | The size of the whole table                                                      |
| xsdt_address      | uint64_t                                                                                                                            | The Address of the XSDT (when available this should be used instead of the RSDT) |
| checksum_extended | uint8_t                                                                                                                             | Used to calculate the checksum of the whole table                                |
| reserved          | uint8_t[3]                                                                                                                          | Can be ignored                                                                   |