Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
5.2.22 Boot Graphics Resource Table (BGRT)
The Boot Graphics Resource Table (BGRT) is an optional table that provides a mechanism to
indicate that an image was drawn on the screen during boot, and some information about the image.
The table is written when the image is drawn on the screen. This should be done after it is expected
that any firmware components that may write to the screen are done doing so and it is known that the
image is the only thing on the screen. If the boot path is interrupted (e.g., by a key press), the valid
bit within the status field should be changed to 0 to indicate to the OS that the current image is
invalidated.
This table is only supported on UEFI systems.
Table 5-103 Boot Graphics Resource Table Fields
Field
Byte
Length
Byte
Offset
Description
Header
Signature 4 0 “BGRT” Signature for the table.
Length 4 4 Length, in bytes, of the entire table
Revision 1 8 1
Checksum 1 9 Entire table must sum to zero.
OEMID 6 10 OEM ID
OEM Table ID 8 16 The table ID is the manufacturer model ID.
OEM Revision 4 24 OEM revision for supplied OEM Table ID.
Creator ID 4 28 Vendor ID of utility that created the table.
Creator Revision 4 32 Revision of utility that created the table.
Version 2 36 2-bytes (16 bit) version ID. This value must be 1.
Status 1 38 1-byte status field indicating current status about the table.
Bits [7:1] = Reserved (must be zero)
Bit [0] = Displayed. A one indicates the boot image graphic is
displayed.
Image Type 1 39 1-byte enumerated type field indicating format of the image.
0 = Bitmap
1 – 255 Reserved (for future use)
Image Address 8 40 8-byte (64 bit) physical address pointing to the firmware’s inmemory
copy of the image bitmap.
Image Offset X 4 48 A 4-byte (32-bit) unsigned long describing the display X-offset of
the boot image. (X, Y) display offset of the top left corner of the
boot image. The top left corner of the display is at offset (0, 0).
Image Offset Y 4 52 A 4-byte (32-bit) unsigned long describing the display Y-offset of
the boot image. (X, Y) display offset of the top left corner of the
boot image. The top left corner of the display is at offset (0, 0).
The BGRT is a dynamic ACPI table that enables boot firmware to provide OPSM with a pointer to
the location in memory where the boot graphics image is stored.
188 April, 2015 Version 6.0