#include <dos.h>
#include <stdio.h>

int COMPort = 0;
unsigned long IRQCount[16];

void HandleInterrupt(int IRQNumber)
{
  unsigned char Status = inportb(COMPort + 2) & 0x0F;
  switch(Status)
  {
    case 1: // This happens after we've changed the OUT2 line state
	    break;
    case 0: // Clear the interrupt state by reading the Modem Status Register
	    inportb(COMPort + 6);
	    break;
    case 2: // Clear the interrupt state by reading the Interrupt Identification Register
	    //                        or by writing into the Transmit Holding Register
	    inportb(COMPort + 2);
	    break;
    case 4: // Clear the interrupt state by reading the received data
	    printf("%c", inportb(COMPort + 0));
	    break;
    case 6: // Clear the interrupt state by reading the Line Status Register
	    if(inportb(COMPort + 5) & 0x01)
	      inportb(COMPort + 0);        // a byte was available (read it now)
	    break;
    case 12: // Clear the interrupt state by reading the Receiver Buffer Register
	     inportb(COMPort + 0);
	     break;
    default: // hmmm, should not have happened (but it did!)
	     ;
  }

  // Increase the counter and send an EOI
  IRQCount[IRQNumber] ++;
  if(IRQNumber >= 8)
    outportb(0xA0, 0x20);
  outportb(0x20, 0x20);
}

void interrupt Interrupt03(...)
{
  HandleInterrupt(3);
}

void interrupt Interrupt04(...)
{
  HandleInterrupt(4);
}

void interrupt Interrupt05(...)
{
  HandleInterrupt(5);
}

void interrupt Interrupt06(...)
{
  HandleInterrupt(6);
}

void interrupt Interrupt07(...)
{
  HandleInterrupt(7);
}

void interrupt Interrupt08(...)
{
  HandleInterrupt(8);
}

void interrupt Interrupt09(...)
{
  HandleInterrupt(9);
}

void interrupt Interrupt10(...)
{
  HandleInterrupt(10);
}

void interrupt Interrupt11(...)
{
  HandleInterrupt(11);
}

void interrupt Interrupt12(...)
{
  HandleInterrupt(12);
}

void interrupt Interrupt13(...)
{
  HandleInterrupt(13);
}

void interrupt Interrupt14(...)
{
  HandleInterrupt(14);
}

void interrupt Interrupt15(...)
{
  HandleInterrupt(15);
}

void Init(int far *COMPorts)
{
  for(int COMPortNumber = 0; COMPortNumber < 4; COMPortNumber ++)
  {
    // Stop if the last UART has been initialised
    COMPort = COMPorts[COMPortNumber];
    if(!COMPort)
      continue;

    outportb(COMPort + 3, inportb(COMPort + 3) & 0x7F);

    inportb(COMPort + 2);
    while(inportb(COMPort + 5) & 1)
      inportb(COMPort);
    inportb(COMPort + 6);

    outportb(COMPort + 1, 0x0F - 2);	// we don't care about TR being empty
    outportb(COMPort + 2, 0x01);

    inportb(COMPort + 2);

    // Handle some waiting IRQ's
    char OldMask1 = inportb(0x21);
    char OldMask2 = inportb(0xA1);
    outportb(0x21, 0);
    outportb(0xA1, 0);
    outportb(COMPort + 4, 0x00);
    outportb(0x21, OldMask1);
    outportb(0xA1, OldMask2);
  }
}

void main(void)
{
  int i, COMPort;
  int far *COMPorts = (int far *) MK_FP(0x0000, 0x0400);

  // Print some info
  printf("UART IRQ Detector 1.0 (made by Peter Lemmens)\n\n");

  // Save the interrupt vectors
  void interrupt (*OudeInterrupt03)(...) = getvect(0x0B);
  void interrupt (*OudeInterrupt04)(...) = getvect(0x0C);
  void interrupt (*OudeInterrupt05)(...) = getvect(0x0D);
  void interrupt (*OudeInterrupt06)(...) = getvect(0x0E);
  void interrupt (*OudeInterrupt07)(...) = getvect(0x0F);
  void interrupt (*OudeInterrupt08)(...) = getvect(0x70);
  void interrupt (*OudeInterrupt09)(...) = getvect(0x71);
  void interrupt (*OudeInterrupt10)(...) = getvect(0x72);
  void interrupt (*OudeInterrupt11)(...) = getvect(0x73);
  void interrupt (*OudeInterrupt12)(...) = getvect(0x74);
  void interrupt (*OudeInterrupt13)(...) = getvect(0x75);
  void interrupt (*OudeInterrupt14)(...) = getvect(0x76);
  void interrupt (*OudeInterrupt15)(...) = getvect(0x77);

  // Get control over the interrupt vectors
  setvect(0x0B, Interrupt03);
  setvect(0x0C, Interrupt04);
  setvect(0x0D, Interrupt05);
  setvect(0x0E, Interrupt08);
  setvect(0x0F, Interrupt07);
  setvect(0x70, Interrupt08);
  setvect(0x71, Interrupt09);
  setvect(0x72, Interrupt10);
  setvect(0x73, Interrupt11);
  setvect(0x74, Interrupt12);
  setvect(0x75, Interrupt13);
  setvect(0x76, Interrupt14);
  setvect(0x77, Interrupt15);

  // Initialise and check the IRQ's
  Init(COMPorts);
  for(int COMPortNumber = 0; COMPortNumber < 4; COMPortNumber ++)
  {
    // Stop if the last UART has been checked
    COMPort = COMPorts[COMPortNumber];
    if(!COMPort)
      continue;

    // Save the IRQ mask
    unsigned char OldMask1 = inportb(0x21);
    unsigned char OldMask2 = inportb(0xA1);

    // Reset the IRQ counters
    for(i = 0; i < 16; i ++)
      IRQCount[i] = 0;

    // Set the correct IRQ mask (all IRQ's may occur)
    outportb(0x21, 0x00);
    outportb(0xA1, 0x00);

    // Trigger the IRQ
    outportb(COMPort + 4, inportb(COMPort + 4) ^ 8);
    outportb(COMPort + 4, inportb(COMPort + 4) ^ 8);

    // Print the IRQ numbers that occured
    int IRQValidated = 0;
    printf("  COM%d (0x%03X): ", COMPortNumber + 1, COMPort);
    for(i = 0; i < 16; i ++)
      if(IRQCount[i])
      {
	// This happens if another device has triggered an IRQ
	if(IRQValidated)
	  printf(" or ");
	IRQValidated ++;

	// Print it
	printf("IRQ %d", i);
      }
    if(!IRQValidated)
      printf("Unknown IRQ");
    printf("\n");

    // Restore the IRQ mask
    outportb(0x21, OldMask1);
    outportb(0xA1, OldMask2);
  }
  printf("\n");

  // Restore the interrupt vectors
  setvect(0x77, OudeInterrupt15);
  setvect(0x76, OudeInterrupt14);
  setvect(0x75, OudeInterrupt13);
  setvect(0x74, OudeInterrupt12);
  setvect(0x73, OudeInterrupt11);
  setvect(0x72, OudeInterrupt10);
  setvect(0x71, OudeInterrupt09);
  setvect(0x70, OudeInterrupt08);
  setvect(0x0F, OudeInterrupt07);
  setvect(0x0E, OudeInterrupt06);
  setvect(0x0D, OudeInterrupt05);
  setvect(0x0C, OudeInterrupt04);
  setvect(0x0B, OudeInterrupt03);
}