FADT: Difference between revisions
Jump to navigation
Jump to search
| [unchecked revision] | [unchecked revision] |
Content added Content deleted
No edit summary |
(Undo revision 11221 because it used non-C types and serialization was not properly handled (in C, there may be gaps between fields)) |
||
| Line 2: | Line 2: | ||
==Finding the FADT== |
==Finding the FADT== |
||
The FADT is pointed to by an entry in the [[RSDT]]. The signature is 'FACP' |
The FADT is pointed to by an entry in the [[RSDT]]. The signature is 'FACP'. |
||
==Structure== |
==Structure== |
||
The FADT |
The FADT contains pointers to two additional tables (in addition to a lot of other information): |
||
* The FACS (Firmware ACPI Control Structure) at offset 36 (4 byte physical address) |
|||
<source lang="c">struct FADT { |
|||
* The DSDT (Differentiated System Description Table) at offset 40 (4 byte physical address) |
|||
struct ACPISDTHeader h; |
|||
DWORD FirmwareCtrl; |
|||
DWORD Dsdt; |
|||
BYTE Reserved; // Was used in ACPI 1.0. Today is not used anymore. Some bioses still use it for compatibility with old os. for more info see the ACPI specification 1.0 |
|||
BYTE PreferredPowerManagementProfile; |
|||
WORD SCI_Interrupt; |
|||
DWORD SMI_CommandPort; |
|||
BYTE AcpiEnable; |
|||
BYTE AcpiDisable; |
|||
BYTE S4BIOS_REQ; |
|||
BYTE PSTATE_Control; |
|||
DWORD PM1aEventBlock; |
|||
DWORD PM1bEventBlock; |
|||
DWORD PM1aControlBlock; |
|||
DWORD PM1bControlBlock; |
|||
DWORD PM2ControlBlock; |
|||
DWORD PMTimerBlock; |
|||
DWORD GPE0Block; |
|||
DWORD GPE1Block; |
|||
BYTE PM1EventLength; |
|||
BYTE PM1ControlLength; |
|||
BYTE PM2ControlLength; |
|||
BYTE PMTimerLength; |
|||
BYTE GPE0Length; |
|||
BYTE GPE1Length; |
|||
BYTE GPE1Base; |
|||
BYTE CStateControl; |
|||
WORD WorstC2Latency; |
|||
WORD WorstC3Latency; |
|||
WORD FlushSize; |
|||
WORD FlushStride; |
|||
BYTE DutyOffset; |
|||
BYTE DutyWidth; |
|||
BYTE DayAlarm; |
|||
BYTE MonthAlarm; |
|||
BYTE Century; |
|||
WORD BootArchitectureFlags; |
|||
BYTE Reserved2; |
|||
DWORD Flags; |
|||
GenericAddressStructure ResetRet; // For details see below. Just know that GenericAddressStructure is made of 12 bytes |
|||
BYTE ResetValue; |
|||
BYTE Reserved3[3]; |
|||
// 64bit pointers |
|||
QWORD X_FirmwareControl; |
|||
QWORD X_Dsdt; |
|||
GenericAddressStructure X_PM1aEventBlock; |
|||
GenericAddressStructure X_PM1bEventBlock; |
|||
GenericAddressStructure X_PM1aControlBlock; |
|||
GenericAddressStructure X_PM1bControlBlock; |
|||
GenericAddressStructure X_PM2ControlBlock; |
|||
GenericAddressStructure X_PMTimerBlock; |
|||
GenericAddressStructure X_GPE0Block; |
|||
GenericAddressStructure X_GPE1Block; |
|||
};</source> |
|||
== GenericAddressStructure == |
|||
Before going to far, keep in mind that the GAS is a structure used by ACPI to describe the position of registers. Its structure is: |
|||
<source lang="c">struct GenericAddressStructure |
|||
{ |
|||
BYTE AddressSpace; |
|||
BYTE BitWidth; |
|||
BYTE BitOffset; |
|||
BYTE AccessSize; |
|||
QWORD Address; |
|||
};</source> |
|||
'''AddressSpace''' can be one of the following: |
|||
* 0 System Memory |
|||
* 1 System I/O |
|||
* 2 PCI Configuration Space |
|||
* 3 Embedded Controller |
|||
* 4 SMBus |
|||
* 5 to 0x7E Reserved |
|||
* 0x7F Functional Fixed Hardware |
|||
* 0x80 to 0xBF Reserved |
|||
* 0xC0 to 0xFF OEM Defined |
|||
'''BitWidth''' and '''BitOffset''' are required only when accessing a bit field. |
|||
'''AccessSize''' defines how many bytes at once you can read/write and it must be one of the following: |
|||
* 0 Undefined (legacy reasons) |
|||
* 1 Byte access |
|||
* 2 Word access |
|||
* 3 Dword access |
|||
* 4 QWord access |
|||
Address is a 64bit pointer in the defined address space to the data structure. |
|||
== Fields == |
|||
'''TODO''' |
|||
== What's next? == |
|||
You should preserve the pointer to the Facs (in FirmwareControl (if < 4gb) or in X_FirmwareControl (if >= 4gb)). Then you should parse the [[DSDT]]. |
|||
Revision as of 05:33, 10 March 2011
FADT (Fixed ACPI Description Table) is a data structure used in the ACPI programming interface. This table contains information about fixed register blocks pertaining to power management.
Finding the FADT
The FADT is pointed to by an entry in the RSDT. The signature is 'FACP'.
Structure
The FADT contains pointers to two additional tables (in addition to a lot of other information):
- The FACS (Firmware ACPI Control Structure) at offset 36 (4 byte physical address)
- The DSDT (Differentiated System Description Table) at offset 40 (4 byte physical address)