fusd/examples/console-read.c

   1 /*
   2  *
   3  * Copyright (c) 2003 The Regents of the University of California.  All
   4  * rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * - Redistributions of source code must retain the above copyright
  11  *   notice, this list of conditions and the following disclaimer.
  12  *
  13  * - Neither the name of the University nor the names of its
  14  *   contributors may be used to endorse or promote products derived
  15  *   from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS''
  18  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  19  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  20  * PARTICULAR  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR
  21  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  22  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  23  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  24  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  25  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  27  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  *
  29  */
  30
  31
  32 /*
  33  * FUSD - The Framework for UserSpace Devices - Example program
  34  *
  35  * Jeremy Elson <jelson@circlemud.org>
  36  *
  37  * console-read: This example demonstrates the easiest possible way to
  38  * block a client system call: by blocking the driver itself.  Not
  39  * recommended for anything but the most trivial drivers -- if you
  40  * need a template from which to start on a real driver, use pager.c
  41  * instead.
  42  *
  43  * $Id$
  44  */
  45
  46 #include <stdio.h>
  47 #include <string.h>
  48 #include <errno.h>
  49
  50 #include "fusd.h"
  51
  52 #define MIN(x, y) ((x) < (y) ? (x) : (y))
  53
  54 int do_open_or_close(struct fusd_file_info *file)
  55 {
  56   return 0; /* attempts to open and close this file always succeed */
  57 }
  58
  59 /* EXAMPLE START console-read.c */
  60 ssize_t do_read(struct fusd_file_info *file, char *user_buffer,
  61             size_t user_length, loff_t *offset)
  62 {
  63   char buf[128];
  64
  65   if (*offset > 0)
  66     return 0;
  67
  68   /* print a prompt */
  69   printf("Got a read from pid %d.  What do we say?\n> ", file->pid);
  70   fflush(stdout);
  71
  72   /* get a response from the console */
  73   if (fgets(buf, sizeof(buf) - 1, stdin) == NULL)
  74     return 0;
  75
  76   /* compute length of the response, and return */
  77   user_length = MIN(user_length, strlen(buf));
  78   memcpy(user_buffer, buf, user_length);
  79   *offset += user_length;
  80   return user_length;
  81 }
  82 /* EXAMPLE STOP */
  83
  84 int main(int argc, char *argv[])
  85 {
  86   struct fusd_file_operations fops = {
  87     open: do_open_or_close,
  88     read: do_read,
  89     close: do_open_or_close };
  90
  91   if (fusd_register("/dev/console-read", "test", "console-read", 0666, NULL, &fops) < 0)
  92     perror("Unable to register device");
  93   else {
  94     printf("/dev/console-read should now exist - calling fusd_run...\n");
  95     fusd_run();
  96   }
  97   return 0;
  98 }
  99