The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/dev/nullcons_subr.c

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    1 /*      $NetBSD: nullcons_subr.c,v 1.13 2014/07/25 08:10:35 dholland Exp $      */
    2 
    3 /*-
    4  * Copyright (c) 2003 The NetBSD Foundation, Inc.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   26  * POSSIBILITY OF SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __KERNEL_RCSID(0, "$NetBSD: nullcons_subr.c,v 1.13 2014/07/25 08:10:35 dholland Exp $");
   31 
   32 #include <sys/param.h>
   33 #include <sys/proc.h>
   34 #include <sys/systm.h>
   35 #include <sys/buf.h>
   36 #include <sys/ioctl.h>
   37 #include <sys/tty.h>
   38 #include <sys/file.h>
   39 #include <sys/conf.h>
   40 #include <sys/vnode.h>
   41 
   42 #include <dev/cons.h>
   43 
   44 static struct tty *nulltty;             /* null console tty */
   45 
   46 cons_decl(null);
   47 
   48 dev_type_read(nullcndev_read);
   49 dev_type_ioctl(nullcndev_ioctl);
   50 dev_type_tty(nullcndev_tty);
   51 
   52 static int      nullcons_newdev(struct consdev *);
   53 
   54 const struct cdevsw nullcn_devsw = {
   55         .d_open = nullopen,
   56         .d_close = nullclose,
   57         .d_read = nullcndev_read,
   58         .d_write = nullwrite,
   59         .d_ioctl = nullcndev_ioctl,
   60         .d_stop = nullstop,
   61         .d_tty = nullcndev_tty,
   62         .d_poll = nopoll,
   63         .d_mmap = nommap,
   64         .d_kqfilter = ttykqfilter,
   65         .d_discard = nodiscard,
   66         .d_flag = D_TTY
   67 };
   68 
   69 /*
   70  * null console device. We need it because of the ioctl() it handles,
   71  * which in particular allows control terminal allocation through
   72  * TIOCSCTTY ioctl. Without the latter, system won't even boot past init(8)
   73  * invocation.
   74  */
   75 int
   76 nullcndev_read(dev_t dev, struct uio *uio, int flag)
   77 {
   78 
   79         return EIO;
   80 }
   81 
   82 int
   83 nullcndev_ioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
   84 {
   85         int error;
   86 
   87         error = (*nulltty->t_linesw->l_ioctl)(nulltty, cmd, data, flag, l);
   88         if (error != EPASSTHROUGH)
   89                 return error;
   90 
   91         error = ttioctl(nulltty, cmd, data, flag, l);
   92         if (error != EPASSTHROUGH)
   93                 return error;
   94 
   95         return 0;
   96 }
   97 
   98 struct tty*
   99 nullcndev_tty(dev_t dev)
  100 {
  101 
  102         return nulltty;
  103 }
  104 
  105 /*
  106  * Mark console as no-op (null) console. Proper initialization is deferred
  107  * to nullconsattach().
  108  */
  109 void
  110 nullcnprobe(struct consdev *cn)
  111 {
  112 
  113         cn->cn_pri = CN_NULL;
  114         cn->cn_dev = NODEV;
  115 }
  116 
  117 /*
  118  * null console initialization. This includes allocation of a new device and
  119  * a new tty.
  120  */
  121 void
  122 nullcninit(struct consdev *cn)
  123 {
  124         static struct consdev nullcn = cons_init(null);
  125 
  126         nullcnprobe(&nullcn);
  127         cn_tab = &nullcn;
  128 }
  129 
  130 /*
  131  * Dumb getc() implementation. Simply blocks on call.
  132  */
  133 int
  134 nullcngetc(dev_t dev)
  135 {
  136 
  137         for (;;)
  138                 ;
  139         return 0;
  140 }
  141 
  142 /*
  143  * Dumb putc() implementation.
  144  */
  145 void
  146 nullcnputc(dev_t dev, int c)
  147 {
  148 
  149 }
  150 
  151 /*
  152  * Allocate a new console device and a tty to handle console ioctls.
  153  */
  154 int
  155 nullcons_newdev(struct consdev *cn)
  156 {
  157         int error;
  158         int bmajor = -1, cmajor = -1;
  159 
  160         if ((cn == NULL) || (cn->cn_pri != CN_NULL) || (cn->cn_dev != NODEV))
  161                 return 0;
  162 
  163         /*
  164          * Attach no-op device to the device list.
  165          */
  166         error = devsw_attach("nullcn", NULL, &bmajor, &nullcn_devsw, &cmajor);
  167         if (error != 0)
  168                 return error;
  169 
  170         /*
  171          * Allocate tty (mostly to have sane ioctl()).
  172          */
  173         nulltty = tty_alloc();
  174         nulltty->t_dev = makedev(cmajor, 0);
  175         tty_attach(nulltty);
  176         cn->cn_dev = nulltty->t_dev;
  177 
  178         return 0;
  179 }
  180 
  181 /*
  182  * Pseudo-device attach function -- it's the right time to do the rest of
  183  * initialization.
  184  */
  185 void
  186 nullconsattach(int pdev_count)
  187 {
  188 
  189         nullcons_newdev(cn_tab);
  190 }

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