/*****************************************************************************
 *                                                                           *
 *                                 V E S A                                   *
 *                                                                           *
 *---------------------------------------------------------------------------*
 * Beschreibung:    VESA-Treiber ueber 16-Bit BIOS.                          *
 *                                                                           *
 * Autor:           Michael Schoettner, HHU, 18.3.2017                       *
 *****************************************************************************/


#include "devices/VESA.h"
#include "kernel/BIOS.h"
#include "kernel/Globals.h"


// Informationen ueber einen VESA-Grafikmodus
// (siehe http://wiki.osdev.org/VESA_Video_Modes)
struct VbeModeInfoBlock {
    unsigned short  attributes;
    unsigned char   winA,winB;
    unsigned short  granularity;
    unsigned short  winsize;
    unsigned short  segmentA, segmentB;
    unsigned short  realFctPtr[2];
    unsigned short  pitch;          // Bytes pro Scanline
    
    unsigned short  Xres, Yres;
    unsigned char   Wchar, Ychar, planes, bpp, banks;
    unsigned char   memory_model, bank_size, image_pages;
    unsigned char   reserved0;
    
    unsigned char   red_mask, red_position;
    unsigned char   green_mask, green_position;
    unsigned char   blue_mask, blue_position;
    unsigned char   rsv_mask, rsv_position;
    unsigned char   directcolor_attributes;
    
    unsigned int    physbase;       // Adresse des Linear-Framebuffers
    unsigned int    OffScreenMemOffset;
    unsigned short  OffScreenMemSize;
} __attribute__((packed));


// Informationen ueber die Grafikkarte
// (siehe http://wiki.osdev.org/VESA_Video_Modes)
struct VbeInfoBlock {
    char            VbeSignature[4];        // == "VESA"
    unsigned short  VbeVersion;             // == 0x0300 for VBE 3.0
    unsigned short  OemStringPtr[2];        // isa vbeFarPtr
    unsigned char   Capabilities[4];
    unsigned short  VideoModePtr[2];        // isa vbeFarPtr
    unsigned short  TotalMemory;            // as # of 64KB blocks
} __attribute__((packed));


/*****************************************************************************
 * Methode:         VESA::initTextMode                                       *
 *---------------------------------------------------------------------------*
 * Beschreibung:    Schalter in den Text-Modus 80x25 Zeichen.                *
 *****************************************************************************/
void VESA::initTextMode() {
    BC_params->AX = 0x4f02;     // SVFA BIOS, init mode
    BC_params->BX = 0x4003;     // 80x25
    bios.Int(0x10);
}


/*****************************************************************************
 * Methode:         VESA::initGraphicMode                                    *
 *---------------------------------------------------------------------------*
 * Parameter:       Nummer des Grafikmodus (siehe VESA.h)                    *
 *                                                                           *
 * Beschreibung:    Bestimmten Grafikmodus einschalten. Dies wird durch      *
 *                  einen Aufruf des BIOS gemacht.                           *
 *****************************************************************************/
bool VESA::initGraphicMode(unsigned short mode) {

    // Alle Grafikmodi abfragen
    BC_params->AX = 0x4F00;
    BC_params->ES = RETURN_MEM >> 4;
    BC_params->DI = RETURN_MEM & 0xF;
    bios.Int(0x10);
    
    struct VbeInfoBlock *ib = (struct VbeInfoBlock *) RETURN_MEM;
    
    // Signaturen pruefen
    if (BC_params->AX != 0x004F) {
        kout << "Error: VESA wird nicht unterstuetzt." << endl;
        return false;
    }
    if (ib->VbeSignature[0]!='V' || ib->VbeSignature[1]!='E' ||
        ib->VbeSignature[2]!='S' || ib->VbeSignature[3]!='A' ) {
        kout << "Error: VESA wird nicht unterstuetzt." << endl;
        return false;
    }

//    kout << "TotalVideoMemory:  " << ((ib->TotalMemory*65536) / (1024*1024)) << " MB" << endl;

    // Gewuenschten Grafikmodus aus Antwort suchen
    unsigned short *modePtr = (unsigned short*)( (ib->VideoModePtr[1]<<4) + ib->VideoModePtr[0]);
    for (int i=0; modePtr[i]!=0xFFFF; ++i ) {
        // Gewuenschter Grafikmodus gefunden?
        if (modePtr[i] == mode) {
            struct VbeModeInfoBlock *minf = (struct VbeModeInfoBlock *)RETURN_MEM;
            
            // Weitere Infos ueber diesen Grafikmodus abfragen
            BC_params->AX = 0x4F01;
            BC_params->CX = mode;
            BC_params->ES = RETURN_MEM >> 4;
            BC_params->DI = RETURN_MEM & 0xF;
            bios.Int(0x10);

            // Text-Modi 0-3 haben keinen LFB
            if ( mode > 3 && (minf->attributes & 0x90) == 0 ) {
                kout << "Error: Grafikmodus bietet keinen linearen Framebuffer." << endl;
                return false;
            }
 
            mode_nr = mode;
            xres = minf->Xres;
            yres = minf->Yres;
            bpp  = (int) minf->bpp;
            lfb  = minf->physbase;
            
            hfb  = (unsigned int) new char [xres*yres*bpp/8];
        
            // Grafikmodus einschalten
            BC_params->AX = 0x4f02;   // SVFA BIOS, init mode
            BC_params->BX = mode;
            bios.Int(0x10);
            return true;
        }
    }
    kout << "Error: Grafikmodus nicht gefunden." << endl;
    return false;
}