/*
    -- pcserial.c -- Tony Givargis
    Interrupt driven PC serial interface.
*/

/*---------------------------------------------------------------------------*/

#include <alloc.h>
#include <conio.h>
#include <dos.h>
#include "pcserial.h"

/*---------------------------------------------------------------------------*/

/*
    serialPortTbl

    Stores pointers to (EL_SerialPort*) ADT's for access by the interrupt
    service routines.
*/
static EL_SerialPort* serialPortTbl[2] = { NULL, NULL };

/*---------------------------------------------------------------------------*/

/*
    InterruptVector1

    Interrupt service routine for UART on com 1.
*/
void interrupt far __ISR1(void) {

    /* read and save the character */
    EL_QueuePush(serialPortTbl[0]->queue,
		 (void*)inp(serialPortTbl[0]->comAdr));

    /* send end of interrupt */
    (void)outp(0x20, 0x20);
}

/*---------------------------------------------------------------------------*/

/*
    InterruptVector2

    Interrupt service routine for UART on com 2.
*/
void interrupt far __ISR2(void) {

    /* read and save the character */
    EL_QueuePush(serialPortTbl[1]->queue,
		 (void*)inp(serialPortTbl[1]->comAdr));

    /* send end of interrupt */
    (void)outp(0x20, 0x20);
}

/*---------------------------------------------------------------------------*/

/*
    SetUART

    Activates the UART chip. Returns 1 on success.
*/
static void SetUART(EL_SerialPort* serialPort) {

    /* setup interrupt refrence table */
    serialPortTbl[serialPort->comAdr == 0x2f8 ? 1 : 0] = serialPort;

    /* setup interrupt handler */
    serialPort->oldISR =(void*)getvect(serialPort->comInt);
    setvect(serialPort->comInt, serialPort->comAdr == 0x2f8 ?__ISR2 :__ISR1);

    /* configure the UART */
    (void)outp(serialPort->comAdr+3, 0x80);
    (void)outp(serialPort->comAdr+1, serialPort->baudHi);
    (void)outp(serialPort->comAdr+0, serialPort->baudLo);
    (void)outp(serialPort->comAdr+3, 0x00);
    (void)outp(serialPort->comAdr+3, serialPort->lcr);
    (void)outp(serialPort->comAdr+4, 0x0f);

    /* enable serial interrupts */
    asm cli
    (void)outp(0x21, inp(0x21)&serialPort->pic);
    (void)outp(serialPort->comAdr+1, 0x01);
    asm sti
}

/*---------------------------------------------------------------------------*/

/*
    InitUART

    De-activates the UART chip.
*/
static void ClearUART(EL_SerialPort* serialPort) {

    /* reset modem control register */
    (void)outp(serialPort->comAdr+4, 0x00);

    /* disable serial interrupts */
    asm cli
    (void)outp(0x21, inp(0x21)|~serialPort->pic);
    (void)outp(serialPort->comAdr+1, 0x00);
    asm sti

    /* reset interrupt handler */
    setvect(serialPort->comInt, (void interrupt(*)(void))serialPort->oldISR);

    /* reset interrupt refrence table */
    serialPortTbl[serialPort->comAdr == 0x2f8 ? 1 : 0] = NULL;
}

/*---------------------------------------------------------------------------*/

/*
    EL_SerialPort

    Initializes the (port) and returns an EL_SerialPort* on success or NULL
    otherwise to be use in subsequent calls to serial port functions.
*/
EL_SerialPort* EL_SerialPortCreate(EL_Port port, EL_Parity parity,
				   long baudRate, int dataBits,
				   int stopBits) {

    EL_SerialPort* serialPort;

    /* validate user input */
    if( (port != COM1 && port != COM2) || baudRate < 300 ||
	(parity != NONE && parity != ODD && parity != EVEN) ||
	baudRate > 115200L || (dataBits != 7 && dataBits != 8) ||
	(stopBits != 1 && stopBits != 2) || (serialPortTbl[port] != NULL) ) {

	return NULL;
    }

    /* create serialPort ADT */
    if( (serialPort = malloc(sizeof(EL_SerialPort))) != NULL ) {

	if( (serialPort->queue = EL_QueueCreate()) == NULL ) {

	    /* queue allocation failed */
	    free(serialPort);
	    serialPort = NULL;
	}
	else {

	    /* create machine registers and UART masks */
	    serialPort->comInt = port == COM1 ? 0x00c : 0x00b;
	    serialPort->comAdr = port == COM1 ? 0x3f8 : 0x2f8;
	    serialPort->baudHi = (unsigned)((115200L / baudRate) >> 8);
	    serialPort->baudLo = (unsigned)((115200L / baudRate) & 0x00ff);
	    serialPort->lcr = parity == NONE ? 0x0000 :
			      parity == ODD ? 0x0020 : 0x0030;
	    serialPort->lcr |= dataBits == 7 ? 0x0002 : 0x0003;
	    serialPort->lcr |= stopBits == 1 ? 0x0000 : 0x0004;
	    serialPort->pic = port == COM1 ? 0xef : 0xf7;

	    /* validate user input */
	    SetUART(serialPort);
	}
    }
    return serialPort;
}

/*---------------------------------------------------------------------------*/

/*
    EL_SerialPortClose

    Destroys (serialPort).
*/
void EL_SerialPortDestroy(EL_SerialPort* serialPort) {

    /* clear the UART and de-allocate serialPort */
    ClearUART(serialPort);
    EL_QueueDestroy(serialPort->queue);
    free(serialPort);
}

/*---------------------------------------------------------------------------*/

/*
    EL_SerialPortRead

    Reads from (serialPort) (szBuf) bytes into (buf). Returns the number
    of bytes actually read. The use of EL_SerialPortQueueSize before a call
    to this function is recommended.
*/
unsigned EL_SerialPortRead(EL_SerialPort* serialPort,
			   void* buf, unsigned szBuf) {

    unsigned numRead = 0;

    /* read szBuf bytes while queue is not empty */
    while( szBuf-- && EL_QueueSize(serialPort->queue) > 0 ) {

	((char*)buf)[numRead++] = (char)EL_QueuePop(serialPort->queue);
    }
    return numRead;
}

/*---------------------------------------------------------------------------*/

/*
    EL_SerialPortWrite

    Writes to (serialPort) (szBuf) bytes from (buf).
*/
void EL_SerialPortWrite(EL_SerialPort* serialPort,
			void* buf, unsigned szBuf) {

    /* write szBuf bytes */
    while( szBuf-- > 0 ) {

	/* wait for UART */
	while( !(inp(serialPort->comAdr+5) & 0x20) );

	/* write a byte */
	(void)outp(serialPort->comAdr, *(((char*)buf)++));
    }
}