BGRT

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The Boot Graphics Record Table (BGRT) is an optional ACPI table which contains a pointer to the image that has been drawn during boot.

Contents

Table structure

Offset (hex) Length Description
00 4 Signature 'BGRT'
04 4 Length of the table (in bytes, including header)
08 1 Revision
09 1 Checksum
0a 6 OEM ID
10 8 OEM Table ID
18 4 OEM Revision
1c 4 Creator ID
20 4 Creator revision
24 2 Version ID (must be 1)
26 1 Status
27 1 Image type
28 8 Image address
30 4 Image X offset
34 4 Image Y offset

Fields

Status

Indicates the image's status.

Bits Description
0 Displayed
1:2 Orientation offset
3:7 Reserved (must be 0)

Orientation offset:

  • 0b00: no offset
  • 0b01: 90º
  • 0b10: 180º
  • 0b11: 270º

Image type

0: Image is a bitmap

1-255: Reserved

Image address

64-bit physical address to an in-memory copy of the displayed image. It can be a 24 bit bitmap (0xRRGGBB) or a 32 bit bitmap (0xrrRRGGBB), where lowercase R means reserved.

Image offsets

Describes the offsets to the (X, Y) of the screen for the top left image corner.

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