//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       ACPI, Hardware detection related functions                    //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <init/boot.h>
#include <io/vga.h>
#include <io/acpi.h>
#include <mm/paging.h>

SDTHeader *AcpiSDT = NULL;
SDTHeader *AcpiFADT = NULL;

char IoACPIVersion = 1;

//
// Returns the checksum of the given structure
//
static inline char DoChecksum(void *ptr, size_t size,
                         size_t intermediateSize, ulong reason)
{
    char checksum = 0;
    for (ulong i=0; i < (ulong)size; i++) {
        if (reason && i > (ulong)intermediateSize)
            break;
        checksum += (uchar)((char*)ptr)[i];
    }
    return checksum;
}

//
// Returns the address of the RSDP
//
static inline RSDPDescriptor *IoFindRSDP()
{
    char *rsdp = NULL;


    // Search in EBDA
    for (rsdp = (char *)0x00080000;   // EBDA address
         (ulong)rsdp < (ulong)0x0009FFFF;             // EBDA end
         rsdp++) {

            if (rsdp[0] == 'R' &&
                rsdp[1] == 'S' &&
                rsdp[2] == 'D' &&
                rsdp[3] == ' ' &&
                rsdp[4] == 'P' &&
                rsdp[5] == 'T' &&
                rsdp[6] == 'R' &&
                rsdp[7] == ' '
                ) {
                return (RSDPDescriptor *)rsdp;
            }
        }

    // Search in BDA
    for (rsdp = (char *)0x000E0000;   // BDA address
         (ulong)rsdp < (ulong)0x000FFFFF;             // BDA end
         rsdp++) {

            if (rsdp[0] == 'R' &&
                rsdp[1] == 'S' &&
                rsdp[2] == 'D' &&
                rsdp[3] == ' ' &&
                rsdp[4] == 'P' &&
                rsdp[5] == 'T' &&
                rsdp[6] == 'R' &&
                rsdp[7] == ' '
                ) {
                return (RSDPDescriptor *)rsdp;
            }
        }

    return NULL;
}

//
// R/XSDT Exploration
//
static inline void IoInitRXSDT(void)
{
    char checksum = 1;

    SDTHeader *rxsdt = AcpiSDT;

    // Map the Table Header
    for (ulong i = 0; i < (sizeof(SDTHeader)/KPAGESIZE) + 1; i++) {
        MmMapPage((void*)((ulong)(rxsdt) + i*KPAGESIZE),
                  (void*)((ulong)(rxsdt) + i*KPAGESIZE),
                  PRESENT);
    }

    // Checksum calculation
    checksum = DoChecksum(rxsdt, (size_t)rxsdt->length,
                          0,
                          0
                          );

    if (checksum)
        KeStartPanic("Invalid RSDT checksum : %d vs 0", checksum);

    if (IoACPIVersion == 1) {
        KernLog("\tACPI Root System Table %s (%s) length %d [%p]\n",
            rxsdt->signature,
            rxsdt->OEMID,
            rxsdt->length,
            rxsdt
            );
    } else {
        KernLog("\tACPI Extended System Table %s (%s) length %d [%p]\n",
            rxsdt->signature,
            rxsdt->OEMID,
            rxsdt->length,
            rxsdt
            );
    }
}

//
// RSDP Exploration
//
static inline void IoInitRSDP(void)
{
    char checksum = 1;

    RSDPDescriptor *rsdp = IoFindRSDP();
    if (!rsdp)
        KeStartPanic("ACPI RSDP not found in memory");

    // Checksum calculation
    checksum = DoChecksum(rsdp, (size_t)sizeof(RSDPDescriptor),
                          (size_t)sizeof(struct RSDPLegacy),
                          !rsdp->legacy.revision
                          );

    if (checksum)
        KeStartPanic("Invalid RSDP checksum : %d vs 0", checksum);

    if (rsdp->legacy.revision == 1 || rsdp->legacy.revision >= 3)
        KeStartPanic("Invalid ACPI Revision : %d", rsdp->legacy.revision);

    KernLog("\tACPI Revision %d (OEM %s)\n",
            (uint)rsdp->legacy.revision,
            rsdp->legacy.OEMID
            );

    AcpiSDT = (void *)(ulong)rsdp->legacy.rsdtAddress;

    if (rsdp->legacy.revision) {
        AcpiSDT = (void *)rsdp->xsdtAddress;
        IoACPIVersion = 2;
    }
}

//
// Explore all ACPI Tables
//
static inline void IoSearchAcpiTables(void)
{
    return;
}


//
// Initialise the ACPI by finding tables
//
void IoInitAcpi(void)
{
    if (BtFirmwareInfo.romValid)
        KernLog("\tRom Table is valid at %p\n", BtFirmwareInfo.romTable);

    if (BtFirmwareInfo.apmValid)
        KernLog("\tApm Table is valid at %p\n", BtFirmwareInfo.apmTable);

    // FIND RSDP

    IoInitRSDP();

    IoInitRXSDT();
}