Sophie: lkmpg-1.1.0-23.mga7 noarch

lkmpg-1.1.0-23.mga7.noarch.rpm

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML
><HEAD
><TITLE
>Passing Command Line Arguments to a Module</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
REL="HOME"
TITLE="The Linux Kernel Module Programming Guide"
HREF="index.html"><LINK
REL="UP"
TITLE="Hello World"
HREF="c147.html"><LINK
REL="PREVIOUS"
TITLE="Hello World (part 4): Licensing and Module Documentation"
HREF="x321.html"><LINK
REL="NEXT"
TITLE="Modules Spanning Multiple Files"
HREF="x385.html"></HEAD
><BODY
CLASS="SECT1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>The Linux Kernel Module Programming Guide</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="x321.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 2. Hello World</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="x385.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN354"
></A
>2.6. Passing Command Line Arguments to a Module</H1
><P
>Modules can take command line arguments, but not with the <TT
CLASS="VARNAME"
>argc</TT
>/<TT
CLASS="VARNAME"
>argv</TT
> you might be
	used to.</P
><P
>To allow arguments to be passed to your module, declare the variables that will take the values of the command line
	arguments as global and then use the <TT
CLASS="FUNCTION"
>MODULE_PARM()</TT
> macro, (defined in <TT
CLASS="FILENAME"
>linux/module.h</TT
>) to set the mechanism up.  At runtime, insmod will fill the variables with any
	command line arguments that are given, like <B
CLASS="COMMAND"
>./insmod mymodule.o myvariable=5</B
>.  The variable declarations
	and macros should be placed at the beginning of the module for clarity.  The example code should clear up my admittedly lousy
	explanation.</P
><P
>The <TT
CLASS="FUNCTION"
>MODULE_PARM()</TT
> macro takes 2 arguments: the name of the variable and its type.  The supported
	variable types are "<TT
CLASS="LITERAL"
>b</TT
>": single byte, "<TT
CLASS="LITERAL"
>h</TT
>": short int, "<TT
CLASS="LITERAL"
>i</TT
>": integer,
	"<TT
CLASS="LITERAL"
>l</TT
>": long int and "<TT
CLASS="LITERAL"
>s</TT
>": string, and the integer types can be signed as usual or unsigned.
	Strings should be declared as "<SPAN
CLASS="TYPE"
>char *</SPAN
>" and insmod will allocate memory for them.  You should always try to give
	the variables an initial default value.  This is kernel code, and you should program defensively.  For example:</P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
>    int myint = 3;
    char *mystr;

    MODULE_PARM(myint, "i");
    MODULE_PARM(mystr, "s");
	</PRE
></FONT
></TD
></TR
></TABLE
><P
>Arrays are supported too.  An integer value preceding the type in MODULE_PARM will indicate an array of some maximum
	length.  Two numbers separated by a '-' will give the minimum and maximum number of values.  For example, an array of shorts
	with at least 2 and no more than 4 values could be declared as:</P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
>    int myshortArray[4];
    MODULE_PARM (myintArray, "3-9i");
	</PRE
></FONT
></TD
></TR
></TABLE
><P
>A good use for this is to have the module variable's default values set, like an port or IO address.  If the variables
	contain the default values, then perform autodetection (explained elsewhere).  Otherwise, keep the current value.  This will
	be made clear later on.</P
><P
>Lastly, there's a macro function, <TT
CLASS="FUNCTION"
>MODULE_PARM_DESC()</TT
>, that is used to document arguments that the
	module can take.  It takes two parameters: a variable name and a free form string describing that variable.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN380"
></A
><P
><B
>Example 2-7. hello-5.c</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="PROGRAMLISTING"
>/*  hello-5.c - Demonstrates command line argument passing to a module.
 */
#include &#60;linux/module.h&#62;
#include &#60;linux/kernel.h&#62;
#include &#60;linux/init.h&#62;
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Peiter Jay Salzman");

// These global variables can be set with command line arguments when you insmod
// the module in. 
//
static u8             mybyte = 'A';
static unsigned short myshort = 1;
static int            myint = 20;
static long           mylong = 9999;
static char           *mystring = "blah";
static int            myintArray[2] = { 0, 420 };

/*  Now we're actually setting the mechanism up -- making the variables command
 *  line arguments rather than just a bunch of global variables.
 */
MODULE_PARM(mybyte, "b");
MODULE_PARM(myshort, "h");
MODULE_PARM(myint, "i");
MODULE_PARM(mylong, "l");
MODULE_PARM(mystring, "s");
MODULE_PARM(myintArray, "1-2i");

MODULE_PARM_DESC(mybyte, "This byte really does nothing at all.");
MODULE_PARM_DESC(myshort, "This short is *extremely* important.");
// You get the picture.  Always use a MODULE_PARM_DESC() for each MODULE_PARM().


static int __init hello_5_init(void)
{
   printk(KERN_ALERT "mybyte is an 8 bit integer: %i\n", mybyte);
   printk(KERN_ALERT "myshort is a short integer: %hi\n", myshort);
   printk(KERN_ALERT "myint is an integer: %i\n", myint);
   printk(KERN_ALERT "mylong is a long integer: %li\n", mylong);
   printk(KERN_ALERT "mystring is a string: %s\n", mystring);
	 printk(KERN_ALERT "myintArray is %i and %i\n", myintArray[0], myintArray[1]);
   return 0;
}


static void __exit hello_5_exit(void)
{
   printk(KERN_ALERT "Goodbye, world 5\n");
}


module_init(hello_5_init);
module_exit(hello_5_exit);</PRE
></FONT
></TD
></TR
></TABLE
></DIV
><P
>I would recommend playing around with this code:</P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
>    satan# insmod hello-5.o mystring="bebop" mybyte=255 myintArray=-1
    mybyte is an 8 bit integer: 255
    myshort is a short integer: 1
    myint is an integer: 20
    mylong is a long integer: 9999
    mystring is a string: bebop
    myintArray is -1 and 420
    
    satan# rmmod hello-5
    Goodbye, world 5
    
    satan# insmod hello-5.o mystring="supercalifragilisticexpialidocious" \
    &#62; mybyte=256 myintArray=-1,-1
    mybyte is an 8 bit integer: 0
    myshort is a short integer: 1
    myint is an integer: 20
    mylong is a long integer: 9999
    mystring is a string: supercalifragilisticexpialidocious
    myintArray is -1 and -1
    
    satan# rmmod hello-5
    Goodbye, world 5
    
    satan# insmod hello-5.o mylong=hello
    hello-5.o: invalid argument syntax for mylong: 'h'</PRE
></FONT
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="x321.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="x385.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Hello World (part 4): Licensing and Module Documentation</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="c147.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Modules Spanning Multiple Files</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>