fusd/examples/drums.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  * drums.c: Example of how to pass data to a callback, inspired by
  38  * Alessandro Rubini's similar example in his article for Linux
  39  * Magazine (http://www.linux.it/kerneldocs/devfs/)
  40  *
  41  * This example creates a bunch of devices in the /dev/drums
  42  * directory: /dev/drums/bam, /dev/drums/bum, etc.  If you cat one of
  43  * these devices, it returns a string that's the same as its name.
  44  *
  45  * $Id$
  46  */
  47
  48 #include <stdio.h>
  49 #include <string.h>
  50 #include <errno.h>
  51 #include <unistd.h>
  52
  53 #include "fusd.h"
  54
  55 #define MIN(x, y) ((x) < (y) ? (x) : (y))
  56
  57
  58 /* EXAMPLE START drums.c */
  59 static char *drums_strings[] = {"bam", "bum", "beat", "boom",
  60                                 "bang", "crash", NULL};
  61
  62 ssize_t drums_read(struct fusd_file_info *file, char *user_buffer,
  63                size_t user_length, loff_t *offset)
  64 {
  65   int len;
  66   char sound[128];
  67
  68   /* file->device_info is what we passed to fusd_register when we
  69    * registered the device */
  70   strcpy(sound, (char *) file->device_info);
  71   strcat(sound, "\n");
  72
  73   /* 1st read returns the sound; 2nd returns EOF */
  74   if (*offset != 0)
  75     return 0;
  76
  77   /* NEVER return more data than the user asked for */
  78   len = MIN(user_length, strlen(sound));
  79   memcpy(user_buffer, sound, len);
  80   *offset += len;
  81   return len;
  82 }
  83
  84 /* EXAMPLE STOP drums.c */
  85
  86
  87 int do_open_or_close(struct fusd_file_info *file)
  88 {
  89   return 0; /* opens and closes always succeed */
  90 }
  91
  92
  93 struct fusd_file_operations drums_fops = {
  94   open: do_open_or_close,
  95   read: drums_read,
  96   close: do_open_or_close
  97 };
  98
  99 /* EXAMPLE START drums.c */
 100 int main(int argc, char *argv[])
 101 {
 102   int i;
 103   char buf[128];
 104   char devname[128];
 105
 106   for (i = 0; drums_strings[i] != NULL; i++) {
 107     sprintf(buf, "/dev/drums/%s", drums_strings[i]);
 108     sprintf(devname, "drum%s", drums_strings[i]);
 109     if (fusd_register(buf, "drums", devname, 0666, drums_strings[i], &drums_fops) < 0)
 110       fprintf(stderr, "%s register failed: %m\n", drums_strings[i]);
 111   }
 112
 113   fprintf(stderr, "calling fusd_run...\n");
 114   fusd_run();
 115   return 0;
 116 }
 117 /* EXAMPLE STOP drums.c */