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Protocols — Device Path Protocol
Version 1.10 12/01/02 8-9
Table 8-9. Expanded ACPI Device Path (continued)
Mnemonic
Byte
Offset
Byte
Length
Description
_UIDSTR Varies >=1 Unique ID that is required by ACPI if two devices have the
same _HID. This value must also match the corresponding
_UID/_HID pair in the ACPI name space. This value is
stored as a null-terminated ASCII string. If the length of this
string not including the null-terminator is 0, then the _UID
field is used. If the length of this null-terminated string is
greater than 0, then this field supercedes the _UID field.
The Byte Offset of this field can be computed by adding 16
to the size of the _HIDSTR field.
_CIDSTR Varies >=1 Device’s compatible PnP hardware ID stored as a null-
terminated ASCII string. This value must match at least one
of the compatible device IDs returned by the corresponding
_CID in the ACPI name space. If the length of this string not
including the null-terminator is 0, then the _CID field is used.
If the length of this null-terminated string is greater than 0,
then this field supercedes the _CID field. The Byte Offset of
this field can be computed by adding 16 to the sum of the
sizes of the _HIDSTR and _UIDSTR fields.
8.3.4 Messaging Device Path
This Device Path is used to describe the connection of devices outside the resource domain of the
system. This Device Path can describe physical messaging information like SCSI ID or abstract
information like networking protocol IP addresses.
8.3.4.1 ATAPI Device Path
Table 8-10. ATAPI Device Path
Mnemonic
Byte
Offset
Byte
Length
Description
Type 0 1 Type 3 – Messaging Device Path
Sub-Type 1 1 Sub-Type 1 – ATAPI
Length 2 2 Length of this structure in bytes. Length is 8 bytes.
PrimarySecondary 4 1 Set to zero for primary or one for secondary
SlaveMaster 5 1 Set to zero for master or one for slave mode
Logical Unit Number 6 2 Logical Unit Number