ttyhandler.c

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/* ttyhandler.c - ttyhandler */

#include <xinu.h>

/*------------------------------------------------------------------------
 *  ttyhandler  -  Handle an interrupt for a tty (serial) device
 *------------------------------------------------------------------------
 */
void ttyhandler(uint32 xnum) {
    struct  dentry  *devptr;    /* Address of device control blk*/
    struct  ttycblk *typtr;     /* Pointer to ttytab entry  */  
    struct  uart_csreg *csrptr; /* Address of UART's CSR    */
    uint32  iir = 0;        /* Interrupt identification */
    uint32  lsr = 0;        /* Line status          */


    /* Get CSR address of the device (assume console for now) */

    devptr = (struct dentry *) &devtab[CONSOLE];
    csrptr = (struct uart_csreg *) devptr->dvcsr;

    /* Obtain a pointer to the tty control block */

    typtr = &ttytab[ devptr->dvminor ];

    /* Decode hardware interrupt request from UART device */

        /* Check interrupt identification register */
    iir = csrptr->iir;
        if (iir & UART_IIR_IRQ) {
        return;
        }

    /* Decode the interrupt cause based upon the value extracted    */
    /* from the UART interrupt identification register.  Clear  */
    /* the interrupt source and perform the appropriate handling    */
    /* to coordinate with the upper half of the driver      */

        /* Decode the interrupt cause */

    iir &= UART_IIR_IDMASK;     /* Mask off the interrupt ID */
        switch (iir) {

        /* Receiver line status interrupt (error) */

        case UART_IIR_RLSI:
        lsr = csrptr->lsr;
        if(lsr & UART_LSR_BI) { /* Break Interrupt */

            /* Read the RHR register to acknowledge */

            lsr = csrptr->buffer;
        }
        return;

        /* Receiver data available or timed out */

        case UART_IIR_RDA:
        case UART_IIR_RTO:

        resched_cntl(DEFER_START);

        /* While chars avail. in UART buffer, call ttyhandle_in */

        while ( (csrptr->lsr & UART_LSR_DR) != 0) {
            ttyhandle_in(typtr, csrptr);
                }

        resched_cntl(DEFER_STOP);

        return;

            /* Transmitter output FIFO is empty (i.e., ready for more)  */

        case UART_IIR_THRE:
        ttyhandle_out(typtr, csrptr);
        return;

        /* Modem status change (simply ignore) */

        case UART_IIR_MSC:
        return;
        }
}