7320fd3a30
of supported operations by example read() and write() operations. Inspired by: http://www.daemonnews.org/200010/blueprints.html PR: 16173 Submitted by: sobomax
132 lines
5.4 KiB
Plaintext
132 lines
5.4 KiB
Plaintext
# Copyright (c) 1998 Rajesh Vaidheeswarran
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# 3. All advertising materials mentioning features or use of this software
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# must display the following acknowledgement:
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# This product includes software developed by Rajesh Vaidheeswarran
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# 4. The name Rajesh Vaidheeswarran may not be used to endorse or promote
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# products derived from this software without specific prior written
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# permission.
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#
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# THIS SOFTWARE IS PROVIDED BY RAJESH VAIDHEESWARRAN ``AS IS'' AND ANY
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# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE RAJESH VAIDHEESWARRAN BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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#
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# Copyright (c) 1993 Terrence R. Lambert.
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# 3. All advertising materials mentioning features or use of this software
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# must display the following acknowledgement:
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# This product includes software developed by Terrence R. Lambert.
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# 4. The name Terrence R. Lambert may not be used to endorse or promote
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# products derived from this software without specific prior written
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# permission.
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#
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# THIS SOFTWARE IS PROVIDED BY TERRENCE R. LAMBERT ``AS IS'' AND ANY
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# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE TERRENCE R. LAMBERT BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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#
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# $FreeBSD$
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#
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1.0 Overview
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This is the README file for the sample kld module
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that mimics a character device driver.
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A kld module may be used to load any data or
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program into the kernel that can be made available by
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modifying a table, pointer, or other kernel data to inform
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the kernel that the module should be used instead of the
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previous code/data path.
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Generally, it is assumed that a loadable module is one of
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a set of similar modules (such as a file system or console
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terminal emulation), and that the reference is through a
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table (such as vfssw[]), and that a "special" value is
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assigned to the slots which are allowed to be replaced.
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This is not enforced, so you may use the kld module
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any way you see fit.
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As with the loadable system calls, it may be desirable to
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allow the module loader to replace an *existing* entry to
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try out changes to kernel code without rebuilding and
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booting from the new kernel.
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The idea behind this example is to show some interaction
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with the device driver. Therefore the flow of the code that
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this driver is aimed at is as follows:
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open(2) -> ioctl(2) -> write(2) -> read(2) -> close(2).
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We will first open the device in the /dev/ directory; then
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we will send an ioctl message to it using ioctl(2) call;
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then write a small string via the write(2) call. This string
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we write to the device will be stored in a static buffer,
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and later will be accessible via the read(2) call. Finally,
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we will close(2) our open()'d device so that we may no
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longer make read or write calls on it.
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2.0 Directions
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To test the module, do the following:
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cd module
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make load
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A load message (the copyright) will be printed on the console.
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cd ../test
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make load
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The system call prints a message on the console when called.
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This message will be printed when running "make load" in
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the "test" subdirectory.
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3.0 Recovering resources
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The module consumes memory when loaded; it can be freed up by
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unloading it. To unload it, type the following from the directory
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this file is in:
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cd module
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make unload
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The miscellaneous module will be unloaded by name.
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4.0 END OF DOCUMENT
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