kprintf.c

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#include <xinu.h>
#include <stdarg.h>

/*------------------------------------------------------------------------
 * kputc - use polled I/O to write a character to the console serial line
 *------------------------------------------------------------------------
 */
syscall kputc(
    byte c /* character to write        */
)
{
    struct dentry *devptr;
    volatile struct uart_csreg *csrptr;
    intmask mask;

    /* Disable interrupts */
    mask = disable();

    /* Get CSR address of the console */

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

    /* wait for UART transmit queue to empty */

    while ((csrptr->lsr & UART_LSR_THRE) == 0)
    {
        ;
    }

    /* write the character */

    csrptr->buffer = c;

    /* Honor CRLF - when writing NEWLINE also send CARRIAGE RETURN  */

    if (c == '\n')
    {
        while ((csrptr->lsr & UART_LSR_THRE) == 0)
        {
            ;
        }
        csrptr->buffer = '\r';
    }

    restore(mask);
    return OK;
}

/*------------------------------------------------------------------------
 * kgetc - use polled I/O to read a character from the console serial line
 *------------------------------------------------------------------------
 */
syscall kgetc(void)
{
    int irmask;
    volatile struct uart_csreg *regptr;
    byte c;
    struct dentry *devptr;
    intmask mask;

    /* Disable interrupts */
    mask = disable();

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

    irmask = regptr->ier; /* Save UART interrupt state.   */
    regptr->ier = 0;      /* Disable UART interrupts.     */

    while (0 == (regptr->lsr & UART_LSR_DR))
    {
        ; /* Do Nothing */
    }

    /* Read character from Receive Holding Register */

    c = regptr->rbr;
    regptr->ier = irmask; /* Restore UART interrupts.     */

    restore(mask);
    return c;
}

extern void _doprnt(char *, va_list, int (*)(int), int);

syscall kprintf(char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    _doprnt(fmt, ap, (int (*)(int))kputc, (int)&devtab[CONSOLE]);
    va_end(ap);
    return OK;
}