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# $FreeBSD$ 62# 63 641.0 Overview 65 66 This is the README file for the sample kld module 67 that mimics a character device driver. 68 69 A kld module may be used to load any data or 70 program into the kernel that can be made available by 71 modifying a table, pointer, or other kernel data to inform 72 the kernel that the module should be used instead of the 73 previous code/data path. 74 75 Generally, it is assumed that a loadable module is one of 76 a set of similar modules (such as a file system or console 77 terminal emulation), and that the reference is through a 78 table (such as vfssw[]), and that a "special" value is 79 assigned to the slots which are allowed to be replaced. 80 This is not enforced, so you may use the kld module 81 any way you see fit. 82 83 As with the loadable system calls, it may be desirable to 84 allow the module loader to replace an *existing* entry to 85 try out changes to kernel code without rebuilding and 86 booting from the new kernel. 87 88 The idea behind this example is to show some interaction 89 with the device driver. Therefore the flow of the code that 90 this driver is aimed at is as follows: 91 92 open(2) -> ioctl(2) -> write(2) -> read(2) -> close(2). 93 94 We will first open the device in the /dev/ directory; then 95 we will send an ioctl message to it using ioctl(2) call; 96 then write a small string via the write(2) call. This string 97 we write to the device will be stored in a static buffer, 98 and later will be accessible via the read(2) call. Finally, 99 we will close(2) our open()'d device so that we may no 100 longer make read or write calls on it. 101 1022.0 Directions 103 104 To test the module, do the following: 105 106 cd module 107 make load 108 109 A load message (the copyright) will be printed on the console. 110 111 cd ../test 112 make load 113 114 The system call prints a message on the console when called. 115 This message will be printed when running "make load" in 116 the "test" subdirectory. 117 118 1193.0 Recovering resources 120 121 The module consumes memory when loaded; it can be freed up by 122 unloading it. To unload it, type the following from the directory 123 this file is in: 124 125 cd module 126 make unload 127 128 The miscellaneous module will be unloaded by name. 129 130 1314.0 END OF DOCUMENT 132