bsd/dev/i386/cons.c

   1 /*
   2  * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 /*
  30  * Indirect driver for console
  31  *
  32  * The purpose of this driver is to provide a device node indirection for
  33  * the console device, which can be any tty class device.  It does this by
  34  * externalizing a global pointer "constty", which is then pointed at the
  35  * console tty device.
  36  *
  37  * The default for this pointer is uninitialized; when it is NULL, we fall
  38  * back to the "km" device, which is a tty BSD wrapper device for the
  39  * Platform Expert console device.  When it is non-NULL, we call through
  40  * to the tty device device instead.
  41  *
  42  * The registration for this device node is static, and the devfs init
  43  * code does not externalize a named device for it, to avoid software
  44  * seeing the device and trying to open it.
  45  *
  46  * The upshot of this is that the console driver should not be set as your
  47  * controlling tty, since you will get a reference to a device which does
  48  * not have an actual device node in /dev, so its name cannot be looked up.
  49  */
  50 #include <sys/param.h>
  51 #include <sys/systm.h>
  52 #include <sys/conf.h>
  53 #include <sys/ioctl.h>
  54 #include <sys/tty.h>
  55 #include <sys/proc.h>
  56 #include <sys/uio.h>
  57
  58 struct tty      *constty;               /* current console device */
  59
  60 /*
  61  * The km driver supplied the default console device for the systems
  62  * (usually a raw frame buffer driver, but potentially a serial driver).
  63  */
  64 extern struct tty *km_tty[1];
  65
  66 /*
  67  * cdevsw[] entries for the console device driver
  68  */
  69 int cnopen(__unused dev_t dev, int flag, int devtype, proc_t pp);
  70 int cnclose(__unused dev_t dev, int flag, int mode, proc_t pp);
  71 int cnread(__unused dev_t dev, struct uio *uio, int ioflag);
  72 int cnwrite(__unused dev_t dev, struct uio *uio, int ioflag);
  73 int cnioctl(__unused dev_t dev, u_long cmd, caddr_t addr, int flg, proc_t p);
  74 int cnselect(__unused dev_t dev, int flag, void * wql, proc_t p);
  75
  76 static dev_t
  77 cndev(void)
  78 {
  79         if (constty) {
  80                 return constty->t_dev;
  81         } else {
  82                 return km_tty[0]->t_dev;
  83         }
  84 }
  85
  86 int
  87 cnopen(__unused dev_t dev, int flag, int devtype, struct proc *pp)
  88 {
  89         dev = cndev();
  90         return (*cdevsw[major(dev)].d_open)(dev, flag, devtype, pp);
  91 }
  92
  93
  94 int
  95 cnclose(__unused dev_t dev, int flag, int mode, struct proc *pp)
  96 {
  97         dev = cndev();
  98         return (*cdevsw[major(dev)].d_close)(dev, flag, mode, pp);
  99 }
 100
 101
 102 int
 103 cnread(__unused dev_t dev, struct uio *uio, int ioflag)
 104 {
 105         dev = cndev();
 106         return (*cdevsw[major(dev)].d_read)(dev, uio, ioflag);
 107 }
 108
 109
 110 int
 111 cnwrite(__unused dev_t dev, struct uio *uio, int ioflag)
 112 {
 113         dev = cndev();
 114         return (*cdevsw[major(dev)].d_write)(dev, uio, ioflag);
 115 }
 116
 117
 118 int
 119 cnioctl(__unused dev_t dev, u_long cmd, caddr_t addr, int flag, struct proc *p)
 120 {
 121         dev = cndev();
 122 #if 0
 123         /*
 124          * Superuser can always use this to wrest control of console
 125          * output from the "virtual" console.
 126          *
 127          * XXX Unfortunately, this code doesn't do what the author thougt
 128          * XXX it did; use of the console device, a TIOCCONS would always
 129          * XXX disassociate the console from a virtual terminal and send
 130          * XXX it back to the fake tty.
 131          */
 132         if ((unsigned) cmd == TIOCCONS && constty) {
 133                 int error = proc_suser(p);
 134                 if (!error) {
 135                         constty = NULL;
 136                 }
 137                 return error;
 138         }
 139 #endif  /* 0 */
 140
 141         return (*cdevsw[major(dev)].d_ioctl)(dev, cmd, addr, flag, p);
 142 }
 143
 144
 145 int
 146 cnselect(__unused dev_t dev, int flag, void *wql, struct proc *p)
 147 {
 148         dev = cndev();
 149         return (*cdevsw[major(dev)].d_select)(dev, flag, wql, p);
 150 }