vga.cpp

Go to the documentation of this file.

 
#include <drivers/video/vga.h>
 
using namespace MaxOS;
using namespace MaxOS::drivers;
using namespace MaxOS::drivers::video;
using namespace MaxOS::hardwarecommunication;
 
 
VideoGraphicsArray::VideoGraphicsArray()
: m_misc_port(0x3C2),
  m_crtc_index_port(0x3D4),
  crtc_data_port(0x3D5),
  m_sequence_index_port(0x3C4),
  m_sequence_data_port(0x3C5),
  m_graphics_controller_index_port(0x3CE),
  m_graphics_controller_data_port(0x3CF),
  m_attribute_controller_index_port(0x3C0),
  m_attribute_controller_read_port(0x3C1),
  m_attribute_controller_write_port(0x3C0),
  m_attribute_controller_reset_port(0x3DA)
{
}
 
VideoGraphicsArray::~VideoGraphicsArray() = default;
 
void VideoGraphicsArray::write_registers(uint8_t *registers) {
 
    // Move to the next register
    m_misc_port.write(*(registers++));
 
    // Set the sequencer registers
    for (uint8_t i = 0; i < 5; i++) {
        m_sequence_index_port.write(i);
        m_sequence_data_port.write(*(registers++));
    }
 
    // Clear protection bit to enable writing to CR0-7
    m_crtc_index_port.write(0x03);
    crtc_data_port.write(crtc_data_port.read() | 0x80);
    m_crtc_index_port.write(0x11);
    crtc_data_port.write(crtc_data_port.read() | ~0x80);
 
    // Ensure protection bit is set
    registers[0x03] = registers[0x03] | 0x80;
    registers[0x11] = registers[0x11] & ~0x80;
 
    // Write the CRTC registers
    for (uint8_t i = 0; i < 25; i++) {
        m_crtc_index_port.write(i);
        crtc_data_port.write(*(registers++));
    }
 
    // Write the graphics controller registers
    for (uint8_t i = 0; i < 9; i++) {
        m_graphics_controller_index_port.write(i);
        m_graphics_controller_data_port.write(*(registers++));
    }
 
    // Write the attribute controller registers
    for (uint8_t i = 0; i < 21; i++) {
        m_attribute_controller_reset_port.read();
        m_attribute_controller_index_port.write(i);
        m_attribute_controller_write_port.write(*(registers++));
    }
 
    // Re-Lock CRTC and unblank display
    m_attribute_controller_reset_port.read();
    m_attribute_controller_index_port.write(0x20);
 
}
 
bool VideoGraphicsArray::supports_mode(uint32_t width, uint32_t height, uint32_t colour_depth) {
    return width == 320 && height == 200 && colour_depth == 8;
}
 
bool VideoGraphicsArray::internal_set_mode(uint32_t width, uint32_t height, uint32_t colour_depth) {
 
    //Values from osdev / modes.c
    unsigned char g_320x200x256[] =
            {
                    // MISC
                    0x63,
                    // SEQ
                    0x03, 0x01, 0x0F, 0x00, 0x0E,
                    // CRTC
                    0x5F, 0x4F, 0x50, 0x82, 0x54, 0x80, 0xBF, 0x1F,
                    0x00, 0x41, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                    0x9C, 0x0E, 0x8F, 0x28, 0x40, 0x96, 0xB9, 0xA3,
                    0xFF,
                    // GC
                    0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x05, 0x0F,
                    0xFF,
                    // AC
                    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
                    0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
                    0x41, 0x00, 0x0F, 0x00, 0x00
            };
 
    write_registers(g_320x200x256);
    return true;
}
 
uint8_t *VideoGraphicsArray::get_frame_buffer_segment() {
 
    // Optimise so that don't have to read and write to the port every time
    return (uint8_t *) 0xA0000;
 
    //read data from index number 6
    m_graphics_controller_index_port.write(0x06);
    uint8_t segment_number =
            m_graphics_controller_data_port.read() &
            (3 << 2); //Shift by 2 as only interested in bits 3 & 4 (& 3 so all the other bits are removed)
    switch (segment_number) {
        default:
        case 0 << 2:
            return (uint8_t *) nullptr;
        case 1 << 2:
            return (uint8_t *) 0xA0000;
        case 2 << 2:
            return (uint8_t *) 0xB0000;
        case 3 << 2:
            return (uint8_t *) 0xB8000;
    }
}
 
void VideoGraphicsArray::render_pixel_8_bit(uint32_t x, uint32_t y, uint8_t colour) {
 
    uint8_t *pixel_address = get_frame_buffer_segment() + 320 * y + x;
    *pixel_address = colour;
}
 
uint8_t VideoGraphicsArray::get_rendered_pixel_8_bit(uint32_t x, uint32_t y) {
 
    uint8_t *pixel_address = get_frame_buffer_segment() + 320 * y + x;
    return *pixel_address;
}
 
string VideoGraphicsArray::vendor_name() {
 
    // VGA was made by IBM
    return "IBM";
}
 
string VideoGraphicsArray::device_name() {
    return "VGA compatible graphics card";
}