source: trunk/libs/newlib/src/libgloss/rs6000/mbx-inbyte.c @ 672

/*
 * mbx-inbyte.c -- inbyte function for targets using the eppcbug monitor
 *
 * Copyright (c) 1998 Cygnus Support
 *
 * The authors hereby grant permission to use, copy, modify, distribute,
 * and license this software and its documentation for any purpose, provided
 * that existing copyright notices are retained in all copies and that this
 * notice is included verbatim in any distributions. No written agreement,
 * license, or royalty fee is required for any of the authorized uses.
 * Modifications to this software may be copyrighted by their authors
 * and need not follow the licensing terms described here, provided that
 * the new terms are clearly indicated on the first page of each file where
 * they apply.
 */

#include "ppc-asm.h"

int inbyte(void)
{
    struct {
        unsigned clun;
        unsigned dlun;
        char     *data;
        unsigned len;
        unsigned rsrvd;
        char     buf[4];
    } ipb, *inpb;

    struct {
        int status;
        int cnt;
    } opb, *outpb;

    inpb = &ipb;
    outpb = &opb;

    do {
        inpb->clun = 0;
        inpb->dlun = 0;
        inpb->data = ipb.buf;
        inpb->len  = 1;
        inpb->rsrvd = 0;

        asm volatile (
            "mr  3,%0\n"
            "mr  4,%1\n"
            "li  10,0x200\n"
            "sc"
            : /* no outputs */
            : "r" (inpb), "r" (outpb)
            : "3", "4", "10"
        );
    } while (outpb->status == 0 && outpb->cnt == 0);

    if (outpb->status == 0)
        return ipb.buf[0] & 0xff;

    return -1;
}