1# Copyright (c) 1998 Rajesh Vaidheeswarran
2# All rights reserved.
3#
4# Redistribution and use in source and binary forms, with or without
5# modification, are permitted provided that the following conditions
6# are met:
7# 1. Redistributions of source code must retain the above copyright
8# notice, this list of conditions and the following disclaimer.
9# 2. Redistributions in binary form must reproduce the above copyright
10# notice, this list of conditions and the following disclaimer in the
11# documentation and/or other materials provided with the distribution.
12# 3. All advertising materials mentioning features or use of this software
13# must display the following acknowledgement:
14# This product includes software developed by Rajesh Vaidheeswarran
15# 4. The name Rajesh Vaidheeswarran may not be used to endorse or promote
16# products derived from this software without specific prior written
17# permission.
18#
19# THIS SOFTWARE IS PROVIDED BY RAJESH VAIDHEESWARRAN ``AS IS'' AND ANY
20# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22# ARE DISCLAIMED. IN NO EVENT SHALL THE RAJESH VAIDHEESWARRAN BE LIABLE
23# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29# SUCH DAMAGE.
30#
31# Copyright (c) 1993 Terrence R. Lambert.
32# All rights reserved.
33#
34# Redistribution and use in source and binary forms, with or without
35# modification, are permitted provided that the following conditions
36# are met:
37# 1. Redistributions of source code must retain the above copyright
38# notice, this list of conditions and the following disclaimer.
39# 2. Redistributions in binary form must reproduce the above copyright
40# notice, this list of conditions and the following disclaimer in the
41# documentation and/or other materials provided with the distribution.
42# 3. All advertising materials mentioning features or use of this software
43# must display the following acknowledgement:
44# This product includes software developed by Terrence R. Lambert.
45# 4. The name Terrence R. Lambert may not be used to endorse or promote
46# products derived from this software without specific prior written
47# permission.
48#
49# THIS SOFTWARE IS PROVIDED BY TERRENCE R. LAMBERT ``AS IS'' AND ANY
50# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
51# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
52# ARE DISCLAIMED. IN NO EVENT SHALL THE TERRENCE R. LAMBERT BE LIABLE
53# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
54# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
55# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
56# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
57# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
58# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
59# SUCH DAMAGE.
60#
61# $FreeBSD: src/share/examples/kld/cdev/README,v 1.1.6.1 2000/10/25 09:02:33 sobomax Exp $
62# $DragonFly: src/share/examples/kld/cdev/README,v 1.2 2003/06/17 04:36:57 dillon Exp $
63#
64
651.0 Overview
66
67 This is the README file for the sample kld module
68 that mimics a character device driver.
69
70 A kld module may be used to load any data or
71 program into the kernel that can be made available by
72 modifying a table, pointer, or other kernel data to inform
73 the kernel that the module should be used instead of the
74 previous code/data path.
75
76 Generally, it is assumed that a loadable module is one of
77 a set of similar modules (such as a file system or console
78 terminal emulation), and that the reference is through a
79 table (such as vfssw[]), and that a "special" value is
80 assigned to the slots which are allowed to be replaced.
81 This is not enforced, so you may use the kld module
82 any way you see fit.
83
84 As with the loadable system calls, it may be desirable to
85 allow the module loader to replace an *existing* entry to
86 try out changes to kernel code without rebuilding and
87 booting from the new kernel.
88
89 The idea behind this example is to show some interaction
90 with the device driver. Therefore the flow of the code that
91 this driver is aimed at is as follows:
92
93 open(2) -> ioctl(2) -> write(2) -> read(2) -> close(2).
94
95 We will first open the device in the /dev/ directory; then
96 we will send an ioctl message to it using ioctl(2) call;
97 then write a small string via the write(2) call. This string
98 we write to the device will be stored in a static buffer,
99 and later will be accessible via the read(2) call. Finally,
100 we will close(2) our open()'d device so that we may no
101 longer make read or write calls on it.
102
1032.0 Directions
104
105 To test the module, do the following:
106
107 cd module
108 make load
109
110 A load message (the copyright) will be printed on the console.
111
112 cd ../test
113 make load
114
115 The system call prints a message on the console when called.
116 This message will be printed when running "make load" in
117 the "test" subdirectory.
118
119
1203.0 Recovering resources
121
122 The module consumes memory when loaded; it can be freed up by
123 unloading it. To unload it, type the following from the directory
124 this file is in:
125
126 cd module
127 make unload
128
129 The miscellaneous module will be unloaded by name.
130
131
1324.0 END OF DOCUMENT
133