acpi.h

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/* Copyright (C) 2022 Wildfire Games.
 *
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 * permit persons to whom the Software is furnished to do so, subject to
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 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
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 */
 
/*
 * minimal subset of ACPI
 */
 
#ifndef INCLUDED_ACPI
#define INCLUDED_ACPI
 
#pragma pack(push, 1)
 
// common header for all ACPI tables
struct AcpiTable
{
    char signature[4];
    u32 size;                   // table size [bytes], including header
    u8 revision;
    u8 checksum;                // to make sum of entire table == 0
    char oemId[6];
    char oemTableId[8];
    u32 oemRevision;
    char creatorId[4];
    u32 creatorRevision;
};
 
enum AcpiAddressSpace
{
    // (these are not generally powers-of-two - some values have been omitted.)
    ACPI_AS_MEMORY     = 0,
    ACPI_AS_IO         = 1,
    ACPI_AS_PCI_CONFIG = 2,
    ACPI_AS_SMBUS      = 4
};
 
// address of a struct or register
struct AcpiGenericAddress
{
    u8 addressSpaceId;
    u8 registerBitWidth;
    u8 registerBitOffset;
    u8 accessSize;
    u64 address;
};
 
struct FADT // signature is FACP!
{
    AcpiTable header;
    u8 unused1[40];
    u32 pmTimerPortAddress;
    u8 unused2[16];
    u16 c2Latency;  // [us]
    u16 c3Latency;  // [us]
    u8 unused3[5];
    u8 dutyWidth;
    u8 unused4[6];
    u32 flags;
    // (ACPI4 defines additional fields after this)
 
    bool IsDutyCycleSupported() const
    {
        return dutyWidth != 0;
    }
 
    bool IsC2Supported() const
    {
        return c2Latency <= 100;    // magic value specified by ACPI
    }
 
    bool IsC3Supported() const
    {
        return c3Latency <= 1000;   // see above
    }
};
 
#pragma pack(pop)
 
/**
 * @param signature e.g. "RSDT"
 * @return pointer to internal storage (valid until acpi_Shutdown())
 *
 * note: the first call may be slow, e.g. if a kernel-mode driver is
 * loaded. subsequent requests will be faster since tables are cached.
 **/
const AcpiTable* acpi_GetTable(const char* signature);
 
/**
 * invalidates all pointers returned by acpi_GetTable.
 **/
void acpi_Shutdown();
 
#endif  // #ifndef INCLUDED_ACPI