Imbus/kernelmod_demo
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Imbus 2026-02-24 12:51:52 +01:00
parent 81d8f15a4e
commit 14671c37a5
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23
Makefile
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# This is a standard makefile for building a kernel module.
# It looks a bit backwards compared to a normal makefile, but that's because
# the kernel supplies its own sub-makefile that we use to build the module.
#
# The M= option tells the kernel's makefile where to find the module's source
# files, and the -C option sets the context directory for make.
#
# The obj-m variable tells the kernel's makefile what the module's object file
# should be called. In this case, it's demo_module.o. This is how the sub-makefile
# infers the name of the module's source file.
#
# This build is highly sensitive to compiler version, and requires the system gcc
# to be the same version as the gcc that built the current kernel.
#
# For more info, see: https://www.kernel.org/doc/html/latest/kbuild/modules.html
obj-m = demo_module.o
all:
make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules
clean:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

74
demo_module.c
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#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
/*
* Last compiled with Linux 6.14.5-300.fc42.x86_64
*/
/* Meta Info */
MODULE_DESCRIPTION("Demo kernel module.");
MODULE_VERSION("0.0.1");
MODULE_AUTHOR("Imbus");
MODULE_LICENSE("GPL");
/*
* Hard coded for RPI3
* Usually retrieved via device tree
*/
#define IO_LED 21
#define IO_BUTTON 20
#define IO_OFFSET 0
static struct gpio_desc *led, *button;
/**
* @brief Called on load
*/
static int __init demo_mod_init(void) {
printk(KERN_INFO "Demo module loaded successfully...");
int status;
led = gpio_to_desc(IO_LED + IO_OFFSET);
if (!led) {
printk("gpioctrl - Error getting pin 21\n");
return -ENODEV;
}
button = gpio_to_desc(IO_BUTTON + IO_OFFSET);
if (!button) {
printk("gpioctrl - Error getting pin 20\n");
return -ENODEV;
}
status = gpiod_direction_output(led, 0);
if (status) {
printk("gpioctrl - Error setting pin 20 to output\n");
return status;
}
status = gpiod_direction_input(button);
if (status) {
printk("gpioctrl - Error setting pin 21 to input\n");
return status;
}
gpiod_set_value(led, 1);
printk("gpioctrl - Button is %spressed\n",
gpiod_get_value(button) ? " " : "not ");
return 0;
}
/**
* @brief Called on unload
*/
static void __exit demo_mod_exit(void) {
printk(KERN_INFO "Demo module unloaded successfully...");
}
module_init(demo_mod_init);
module_exit(demo_mod_exit);