Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
6.4.2.7 Fixed DMA Descriptor
Type 0, Small Item Name 0xA, Length = 5
The Fixed DMA descriptor provides a means for platforms to statically assign DMA request lines
and channels to devices connected to a shared DMA controller. This descriptor differs from the
DMA descriptor in that it supports many more DMA request lines and DMA controller channels, as
well as a flexible mapping between the two. The width of the bus used for transfers to the device is
also provided. This structure is repeated for each separate request line/channel pair required, and can
only be used in the _CRS object. (Dynamic arbitration of Fixed DMA resource is not supported.)
Table 6-199 Fixed DMA Resource Descriptor
Offset
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Field Name
Value = 0x55 (01010101B) – Type = 0, Small item name = 0xA, Length = 0x5
DMA Request Line bits [7:0] _DMA[7:0]. A platform-relative number uniquely identifying the
request line assigned. Request line-to-Controller mapping is done in a controller-specific OS
driver.
DMA Request Line bits [15:8] _DMA[15:8]
DMA Channel bits[7:0] _TYP[7:0]. A controller-relative number uniquely identifying the
controller’s logical channel assigned. Channel numbers can be shared by multiple request lines.
DMA Channel bits[15:8] _TYP[15:8]
DMA Transfer Width. _SIZ. Bus width that the device connected to this request line supports.
0x00 8-bit
0x01 16-bit
0x02 32-bit
0x03 64-bit
0x04 128-bit
0x05 256-bit
0x06-0xFF Reserved
6.4.2.8 Vendor-Defined Descriptor
Type 0, Small Item Name 0xE, Length = 1 to 7
The vendor defined resource data type is for vendor use.
Table 6-200 Vendor-Defined Resource Descriptor Definition
Offset
Field Name
Byte 0 Value = 0x71 – 0x77 (01110nnnB) – Type = 0, small item name = 0xE, Length = 1–7
Byte 1 to 7 Vendor defined
See VendorShort (page 900) for a description of the ASL macro that creates a short vendor-defined
resource descriptor.
348 April, 2015 Version 6.0