Specifications

QSSC-S4R Technical Product Specification Operating System Boot, Sleep, and Wake
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19.1.3.3.2 EFI Device Order Table
EFI device orders are similar, but the elements in the Device Order List are WORDs rather than BYTEs (2 + 2n bytes,
where n is the number of EFI devices in the order):
Table 141. BOT EFI Device Order Table
Order
Table
(for non-
EFI
devices)
Offset Name Length Description
00h Order type 1 Byte This field specifies the type of order.
10h = EFI boot order that specifies the order of EFI boot targets.
For other order types, see Section 19.1.3.3.1.
01h Order Length 1 Byte Number of boot device in a particular order list.
02h Device order
list
Order
Length
WORDs
This field contains the ordered list of boot device types or boot
devices.
For an EFI Boot order type, the Device list contains an ordered list
of EFI boot targets. Each boot target is a two-byte number as in
the EFI BootOrder variable. The boot target number associates
the EFI boot device to Boot#### EFI variable, where ####‘
represents the boot target number. Each boot target must have a
device path in the Device name/path field.
19.1.3.4 BOT Device Name(s)
The Device Name section is a series of name records, each beginning with the Type and Number of the device, and
followed by the device‘s name.
EFI Devices include Path as well as Name.
19.1.3.4.1 Non-EFI Device Name
This structure contains the device name (user-readable description) for one device in the boot order data. The name is
optional for legacy, but mandatory for OEM devices. The device name/path data should be used when boot devices
are reported to the user.
A Device Name is (3 + n + 1) bytes, where n is number of characters in the name.
Table 142. BOT Non-EFI Device Name Structure
Device
Name
(for non-
EFI device)
Offset Name Length Description
00h Type 1 Byte Order type.
01h Number 1 Word Device number stored in little endian byte order.
03h Name Varies Null-terminated ASCII string.
19.1.3.4.2 EFI Device Name and Path
This structure contains the device name (user-readable description) and the hardware path data for a device in the
boot order data. The name is optional for EFI boot devices. The device name/path data should be used when the boot
device is reported to the user.
Each device name/path entry starts with a 3-byte device code: first byte represents the order type that the device is
part of and the following 2 bytes represent the device number.
For EFI devices, this field additionally contains the EFI device path to boot the target, which is mandatory. The device
path must comply with the UEFI 2.0 Specification. This field should have the following format for EFI devices:
Table 143. BOT EFI Device Name and Path Structure
EFI
Device
Name
and Path
Offset Name Length Description
00h T
y
pe 1 B
y
te Order t
y
pe = 10h
01h Number 1 Word Device number stored in little endian b
y
te order.
03h Path Length 1 Word Size of Device path in b
y
tes, stored in little endian b
y
te order.