Compilation and loading of Linux kernel driver modules

HOST: Windows 7 flagship edition, vmware7.1.2, fedora9

Compiling environment: Arm-Linux-GCC 4.4.3

Linux: linux-2.6.32.2

Busybox version: busybox-1.19.4

Target Board: friendly arm micro2440

How to compile and use the kernel module:

Write a simple Linux kernel module Hello world and hello. C. The content is as follows:

# Include
<Linux/init. h>

# Include <Linux/module. h>

Module_license ("dual BSD/GPL ");

Static int hello_init (void)

{

Printk (kern_alert
"Hello world enter \ n ");

Return 0;

}

Static void hello_exit (void)

{

Printk (kern_alert
"Hello World exit \ n ");

}

Module_init (hello_init );

Module_exit (hello_exit );

Module_author ("Charles ");

Module_description ("a simple hello World module ");

Module_alias ("a simplest module ");

Compile a simple makefile as follows:

OBJ-M: = Hello. o

Use the following command to compile the hello World module:

# Make-C $ linux_kernel_path M = $ (PWD) Modules

$ Linux_kernel_path is the absolute path of the kernel file. After compilation, the kernel module hello. Ko will be generated in the current directory.

Load, view, and uninstall modules:

# Insmod hello. Ko // load the hello. Ko Module

# Lsmod // view the current loading Module

# Rmmod Hello // uninstall the module without. Ko

Compile and load the LED driver:

Write the LED driver next time. Assume that the LED driver has been written, and the driver file name is micro2440_leds. Copy it to the driver/Char directory and add it to the makefile directory:

OBJ-M + = micro2440_leds.o

Run the following command in the top-level directory of the kernel source code:

# Make M = Drivers/Char/modules

Generate the micro2440_leds.ko file.

Copy micro2440_leds.ko to the target board directory/lib/modules/and load the LED driver module:

# Insmod/lib/modules/micro2440_leds.ko

Problems encountered when the target board is detached from the module:

[Root @ Debian modules] # rmmod micro2440_leds

Rmmod: chdir (2.6.32.2): no such file or directory

The target board has already created/lib/modules/, and the modules that need to be dynamically loaded are stored in this directory. However, an empty directory/lib/modules/2.6.32.2 must be created to uninstall the module, 2.6.32.2 is the corresponding kernel version.

Use make menuconfig to configure the LED driver:

Modify driver/Char/makefile and add the following line:

OBJ-M + = micro2440_leds.o

Changed:

OBJ-$ (config_mini2440_led) + = micro2440_leds.o

Add the following to the konfig file in the corresponding directory:

Config mini2440_led

Tristate "LED driver for friendlyarm mini2440 Development Boards"

Depends on mach_mini2440

Default y if mach_mini2440

Help

This is LED driver for friendlyarm mini2440 Development Boards

Tristate indicates that the driver can be compiled into a module through make menuconfig. The bool type can only be compiled into or not compiled into the kernel. Depends on indicates dependency. Default y indicates that the kernel is compiled by default, which has three options: Y, M, and N. M indicates that the kernel module is compiled, and N indicates that the kernel module is not compiled.

Run make menuconfig again to go to the character device driver page:

Device Drivers --->

Character devices --->

<*> LED driver for friendlyarm mini2440 Development Boards

We found that the LED driver configuration option was added.

Do not modify the Kernel File compilation driver module:

Create a folder named led. Copy the LED driver source code micro2440_leds.c to this directory. Create a makefile in this directory as follows:

OBJ-M: = micro2440_leds.o

Kernel_dir? =/Home/samba/linux-2.6.32.2-micro2440

ALL:

$ (Make)-C $ (kernel_dir) M = $ (PWD) Modules

Clean:

Rm-f *. O *. Ko *. Mod. **. Order *. symvers

After saving the file, run make to generate the required driver module File micro2440_leds.ko in the current directory.