Untitled

uint32_t pci_config_read( uint8_t bus, uint8_t device, uint8_t func, uint16_t content )
{
    // example: PCI_VENDOR_ID 0x0200 ==> length: 0x02 reg: 0x00 offset: 0x00
    uint8_t length  = content >> 8;
    uint8_t reg_off = content & 0x00FF;
    uint8_t reg     = reg_off & 0xFC;     // bit mask: 11111100b
    uint8_t offset  = reg_off % 0x04;     // remainder of modulo operation provides offset

    outportl(PCI_CONFIGURATION_ADDRESS,
        0x80000000
        | (bus    << 16)
        | (device << 11)
        | (func   <<  8)
        | (reg         ));

    // use offset to find searched content
    uint32_t readVal = inportl(PCI_CONFIGURATION_DATA) >> (8 * offset);

    switch(length)
    {
        case 1:
            readVal &= 0x000000FF;
        break;
        case 2:
            readVal &= 0x0000FFFF;
        break;
        case 4:
            readVal &= 0xFFFFFFFF;
        break;
    }
    return readVal;
}

void pci_config_write_byte( uint8_t bus, uint8_t device, uint8_t func, uint8_t reg, uint8_t val )
{
    outportl(PCI_CONFIGURATION_ADDRESS,
        0x80000000
        | (bus     << 16)
        | (device  << 11)
        | (func    <<  8)
        |  reg );

    outportb(PCI_CONFIGURATION_DATA, val);
}

void pci_config_write_dword( uint8_t bus, uint8_t device, uint8_t func, uint8_t reg, uint32_t val )
{
    outportl(PCI_CONFIGURATION_ADDRESS,
        0x80000000
        | (bus     << 16)
        | (device  << 11)
        | (func    <<  8)
        | (reg & 0xFC   ));

    outportl(PCI_CONFIGURATION_DATA, val);
}