//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:  Memory 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 <kernel/base.h>

#define MINIMUM_RAM_SIZE  16    // Mio, the minimum RAM size.

#define AVAILABLE_ZONE    1     // Fully usable RAM zone
#define RESERVED_ZONE     2     // Used by the firmware
#define ACPI_ZONE         3     // Used by ACPI but can be freed
#define NVS_ZONE          4     // Dunno
#define BADRAM_ZONE       5     // Invalid zone because material problem...
#define MAX_ENTRIES       2048  // Max number of memory map entries

// -------------------------------------------------------------------------- //

typedef struct MemoryMap_t MemoryMap_t;
typedef struct MapEntry_t MapEntry_t;
typedef struct GdtEntry_t GdtEntry_t;
typedef struct GdtPtr_t GdtPtr_t;

// -------------------------------------------------------------------------- //
// The entry structure of the map
struct MapEntry_t {
    void *addr;
    size_t length;  // in bytes
    uint type;      // reserved or not
} __attribute__((__packed__));

// the map structure
struct MemoryMap_t {
    size_t length;
    size_t freeRamSize;
    size_t nonfreeRamSize;
    MapEntry_t entry[MAX_ENTRIES];
} __attribute__((__packed__));

// The gdt
struct GdtEntry_t
{
   ushort lowLimit;     // lower 16 bits
   ushort lowBase;      // lower 16 bits
   uchar  middleBase;   // next 8 bits
   uchar  access;       // determine what ring this segment can be used in
   uchar  granularity;
   uchar  highBase;     // last 8 bits
} __attribute__((packed));

struct GdtPtr_t
{
   uchar limit;         // upper 16 bits
   ushort base;         // address of the first entry
}
 __attribute__((packed));

// -------------------------------------------------------------------------- //

//
// Initializes the memory map structure
//
error_t MmInitMemoryMap(void);

//
// Returns the size of the first available memory zone
// from the start address pointer
//
size_t MmGetAvailZoneSize(void *start);

//
// Returns the first available memory zone from the start address pointer
//
void *MmGetFirstAvailZone(void *start);

//
// Initialize the descriptor table
//
void MmInitGdt(void);
// -------------------------------------------------------------------------- //