/* $OpenBSD: gateA20.c,v 1.11 2017/09/08 05:36:52 deraadt Exp $ */ /* * Ported to boot 386BSD by Julian Elischer (julian@tfs.com) Sept 1992 * * Mach Operating System * Copyright (c) 1992, 1991 Carnegie Mellon University * All Rights Reserved. * * Permission to use, copy, modify and distribute this software and its * documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie Mellon * the rights to redistribute these changes. */ #include #include #include #include #include "libsa.h" #define KB_A20 0xdf /* enable A20, enable output buffer full interrupt enable data line enable clock line */ /* * "Probe"-style routine (no parameters) to turn A20 on */ void gateA20on(void) { gateA20(1); } /* * Gate A20 for high memory */ void gateA20(int on) { if (ps2model == 0xf82 || (inb(IO_KBD + KBSTATP) == 0xff && inb(IO_KBD + KBDATAP) == 0xff)) { int data; /* Try to use 0x92 to turn on A20 */ if (on) { data = inb(0x92); outb(0x92, data | 0x2); } else { data = inb(0x92); outb(0x92, data & ~0x2); } } else { while (inb(IO_KBD + KBSTATP) & KBS_IBF); while (inb(IO_KBD + KBSTATP) & KBS_DIB) (void)inb(IO_KBD + KBDATAP); outb(IO_KBD + KBCMDP, KBC_CMDWOUT); while (inb(IO_KBD + KBSTATP) & KBS_IBF); if (on) outb(IO_KBD + KBDATAP, KB_A20); else outb(IO_KBD + KBDATAP, 0xcd); while (inb(IO_KBD + KBSTATP) & KBS_IBF); while (inb(IO_KBD + KBSTATP) & KBS_DIB) (void)inb(IO_KBD + KBDATAP); } }