Advanced Configuration and Power Interface Specification

ACPI Software Programming Model
OperationRegion (
RegionName,
RegionSpace,
Offset,
Length
)
Where:
// NameString
// RegionSpaceKeyword
// TermArg=>Integer
// TermArg=>Integer
• RegionName specifies a name for this region (for example, TOP1).
• RegionSpace must be set to GenericSerialBus (operation region type value 0x09).
• Offset specifies the initial command value offset for the target device. For example, the value
0x00 refers to a command value offset of zero (0). Raw protocols ignore this value.
• Length is set to the 0x100 (256), representing the maximum number of possible command
values.
Note: The Operation Region must be declared within the scope of the Serial Bus controller device.
The following ASL code shows the use of the OperationRegion, Field, and Offset terms as they
apply to SPB space.
Scope(\_SB.I2C){
OperationRegion(TOP1, GenericSerialBus, 0x00, 0x100) // GenericSerialBus device at command
// offset 0x00
Name (SDB0, ResourceTemplate() {
I2CSerialBus(0x4a,,100000,,”\_SB.I2C”,,,,RawDataBuffer(){1,2,3,4,5,6})
})
Field(TOP1, BufferAcc, NoLock, Preserve)
{
Connection(SDB0) // Use the Resource Descriptor defined above
AccessAs(BufferAcc, AttribWord)
// Use the GenericSerialBus Read/Write Word protocol
FLD0, 8, // Virtual register at command value 0.
FLD1, 8 // Virtual register at command value 1.
}
Field(TOP1, BufferAcc, NoLock, Preserve)
{
Connection(I2CSerialBus(0x5a,,100000,,”\_SB.I2C”,,,,RawDataBuffer(){1,6}))
AccessAs(BufferAcc, AttribBytes (16))
FLD2, 8 // Virtual register at command value 0.
}
// Create the GenericSerialBus data buffer
Name(BUFF, Buffer(34){})
CreateByteField(BUFF, 0x00, STAT)
CreateWordField(BUFF, 0x02, DATA)
}
// Create GenericSerialBus data buffer as BUFF
// STAT = Status (Byte)
// DATA = Data (Word)
The Operation Region in this example is defined within the scope of the target controller device,
I2C.
GenericSerialBus regions are only accessible via the Field term (see Section 19.6.46 “Field (Declare
Field Objects)) GenericSerialBus protocols are assigned to field elements using the AccessAs term
(see Section 19.3.4 “ASL Macros”) within the field definition.
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