3 * Copyright (c) 2003 The Regents of the University of California. All
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
10 * - Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
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.
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.
33 * FUSD - The Framework for UserSpace Devices - Example program
35 * Jeremy Elson <jelson@circlemud.org>
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/)
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.
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
60 #define MIN(x, y) ((x) < (y) ? (x) : (y))
63 /* EXAMPLE START drums2.c */
76 /* EXAMPLE START drums2.c */
80 int drums_open(struct fusd_file_info
*file
)
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
;
86 /* Store this user's unique user number in their private_data */
87 file
->private_data
= (void *) ++(d
->num_users
);
89 return 0; /* return success */
92 int drums_read(struct fusd_file_info
*file
, char *user_buffer
,
93 size_t user_length
, loff_t
*offset
)
95 struct drum_info
*d
= (struct drum_info
*) file
->device_info
;
99 sprintf(sound
, "You are user %d to hear a drum go '%s'!\n",
100 (int) file
->private_data
, d
->name
);
102 len
= MIN(user_length
, strlen(sound
));
103 memcpy(user_buffer
, sound
, len
);
109 int drums_close(struct fusd_file_info
*file
)
111 return 0; /* closes always succeed */
115 struct fusd_file_operations drums_fops
= {
121 /* EXAMPLE START drums2.c */
123 int main(int argc
, char *argv
[])
129 for (d
= drums
; d
->name
!= NULL
; d
++) {
130 sprintf(buf
, "/dev/drums/%s", d
->name
);
131 sprintf(devname
, "drum%s", d
->name
);
132 if (fusd_register(buf
, "drums", devname
, 0666, d
, &drums_fops
) < 0)
133 fprintf(stderr
, "%s register failed: %m\n", d
->name
);
138 fprintf(stderr
, "calling fusd_run...\n");