fusd/examples/drums2.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  * drums2.c: Another example of how to pass data to a callback,
  38  * inspired by Alessandro Rubini's similar example in his article for
  39  * Linux Magazine (http://www.linux.it/kerneldocs/devfs/)
  40  *
  41  * Like the original drums.c, this example creates a bunch of devices
  42  * in the /dev/drums directory: /dev/drums/bam, /dev/drums/bum, etc.
  43  * However, it also uses the private_data structure to keep per-file
  44  * state, and return a string unique to each user of the device.
  45  *
  46  * Note, unlike the original drums.c, this driver does not use *offset
  47  * to remember if this user has read before; cat /dev/drums/X will
  48  * read infinitely
  49  *
  50  * $Id$
  51  */
  52
  53 #include <stdio.h>
  54 #include <string.h>
  55 #include <errno.h>
  56 #include <unistd.h>
  57
  58 #include "fusd.h"
  59
  60 #define MIN(x, y) ((x) < (y) ? (x) : (y))
  61
  62
  63 /* EXAMPLE START drums2.c */
  64 struct drum_info {
  65   char *name;
  66   int num_users;
  67 } drums[] = {
  68   { "bam", 0 },
  69   { "bum", 0 },
  70   /* ... */
  71 /* EXAMPLE STOP */
  72   { "beat", 0 },
  73   { "boom", 0 },
  74   { "bang", 0 },
  75   { "crash", 0 },
  76 /* EXAMPLE START drums2.c */
  77   { NULL, 0 }
  78 };
  79
  80 int drums_open(struct fusd_file_info *file)
  81 {
  82   /* file->device_info is what we passed to fusd_register when we
  83    * registered the device.  It's a pointer into the "drums" struct. */
  84   struct drum_info *d = (struct drum_info *) file->device_info;
  85   int *user_num = calloc(1, sizeof(*user_num));
  86
  87   /* Store this user's unique user number in their private_data */
  88   *user_num = ++(d->num_users);
  89   file->private_data = (void *) user_num;
  90
  91   return 0; /* return success */
  92 }
  93
  94 ssize_t drums_read(struct fusd_file_info *file, char *user_buffer,
  95                size_t user_length, loff_t *offset)
  96 {
  97   struct drum_info *d = (struct drum_info *) file->device_info;
  98   int len;
  99   char sound[128];
 100
 101   sprintf(sound, "You are user %d to hear a drum go '%s'!\n",
 102           *(int *) file->private_data, d->name);
 103
 104   len = MIN(user_length, strlen(sound));
 105   memcpy(user_buffer, sound, len);
 106   *offset += len;
 107   return len;
 108 }
 109 /* EXAMPLE STOP */
 110
 111
 112 int drums_close(struct fusd_file_info *file)
 113 {
 114   return 0; /* closes always succeed */
 115 }
 116
 117
 118 struct fusd_file_operations drums_fops = {
 119   open: drums_open,
 120   read: drums_read,
 121   close: drums_close
 122 };
 123
 124 /* EXAMPLE START drums2.c */
 125
 126 int main(int argc, char *argv[])
 127 {
 128   struct drum_info *d;
 129   char buf[128];
 130   char devname[128];
 131
 132   for (d = drums; d->name != NULL; d++) {
 133     sprintf(buf, "/dev/drums/%s", d->name);
 134     sprintf(devname, "drum%s", d->name);
 135     if (fusd_register(buf, "drums", devname, 0666, d, &drums_fops) < 0)
 136       fprintf(stderr, "%s register failed: %m\n", d->name);
 137   }
 138   /* ... */
 139 /* EXAMPLE STOP */
 140
 141   fprintf(stderr, "calling fusd_run...\n");
 142   fusd_run();
 143   return 0;
 144 }
 145
 146
 147