src/newlib/libgloss/rs6000/mbx-inbyte.c

/*
 * 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;
}