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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: drums2.c,v 1.7 2007-12-08 04:05:01 girod Exp $
 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 
 86   /* Store this user's unique user number in their private_data */
 87   file->private_data = (void *)(size_t) ++(d->num_users);
 88 
 89   return 0; /* return success */
 90 }
 91 
 92 ssize_t drums_read(struct fusd_file_info *file, char *user_buffer,
 93                size_t user_length, loff_t *offset)
 94 {
 95   struct drum_info *d = (struct drum_info *) file->device_info;
 96   int len;
 97   char sound[128];
 98 
 99   sprintf(sound, "You are user %d to hear a drum go '%s'!\n",
100           (int)(size_t) file->private_data, d->name);
101 
102   len = MIN(user_length, strlen(sound));
103   memcpy(user_buffer, sound, len);
104   return len;
105 }
106 /* EXAMPLE STOP */
107 
108 
109 int drums_close(struct fusd_file_info *file)
110 {
111   return 0; /* closes always succeed */
112 }
113 
114 
115 struct fusd_file_operations drums_fops = {
116   open: drums_open,
117   read: drums_read,
118   close: drums_close
119 };
120 
121 /* EXAMPLE START drums2.c */
122 
123 int main(int argc, char *argv[])
124 {
125   struct drum_info *d;
126   char buf[128];
127 
128   for (d = drums; d->name != NULL; d++) {
129     sprintf(buf, "/dev/drums/%s", d->name);
130     if (fusd_register(buf, 0666, d, &drums_fops) < 0)
131       fprintf(stderr, "%s register failed: %m\n", d->name);
132   }
133   /* ... */
134 /* EXAMPLE STOP */
135 
136   fprintf(stderr, "calling fusd_run...\n");
137   fusd_run();
138   return 0;
139 }
140 
141 
142 
143
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Linux Cross Reference cvs/emstar/fusd/examples/drums2.c

Linux Cross Reference
cvs/emstar/fusd/examples/drums2.c
