要編譯要先安裝 build-essential 與 libelf-dev 套件， build-essential 包含了編譯 C / C++ 所需的套件，lebelf-dev 則包含編譯 driver (kernel module) 所需的程式。
$ sudo apt-get update $ sudo apt-get install build-essential $ sudo apt-get install libelf-dev
// debug_card.h #ifndef _DEBUG_CARD_H_ #define MSG(format, arg...) printk(KERN_INFO "DEBUG CARD: " format "\n", ## arg) #include <linux/ioctl.h> #define DEV_MAJOR 121 #define DEV_NAME "debug" #define DEV_IOCTLID 0xD0 #define IOCTL_WRITE _IOW(DEV_IOCTLID, 10, int) #define IOCTL_RESET _IOW(DEV_IOCTLID, 0, int) #endif
//debug_card.c
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
//#include <asm/uaccess.h>
#include <linux/uaccess.h>
#include "debug_card.h"
unsigned long IOPort = 0x80;
#define DRIVER_NAME "debug_card"
static unsigned int chrdev_sys_major = 0;
static unsigned int num_of_dev = 1;
static struct cdev debug_card_cdev;
static struct class *chrdev_sys_class = NULL;
void write_debug_card(unsigned int num) {
MSG("write 0x%02X (%d) to debug card", (unsigned char)num, num);
outb((unsigned char)num, IOPort);
}
static long debug_card_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) {
switch (cmd) {
case IOCTL_RESET:
write_debug_card(0x00);
break;
default:
return -1;
}
return 0;
}
ssize_t debug_card_write(struct file *filp, const char *buff,
size_t count, loff_t *offp) {
char *str;
unsigned int num;
int i;
if (count == 0) return 0;
filp->private_data = (char *)kmalloc(64, GFP_KERNEL);
str = filp->private_data;
if (copy_from_user(str, buff, count)) return -EFAULT;
/* atoi() */
num = str[0] - '0'; for (i = 1; i < count; i++) {
num = num * 10 + (str[i] - '0');
}
write_debug_card(num);
return 1;
};
/**************************************************/
int debug_card_release(struct inode *inode, struct file *filp) {
module_put(THIS_MODULE);
kfree(filp->private_data);
return 0;
};
int debug_card_open(struct inode *inode, struct file *filp) {
try_module_get(THIS_MODULE);
return 0;
};
struct file_operations card_fops = {
.owner = THIS_MODULE,
.open = debug_card_open,
.write = debug_card_write,
.release = debug_card_release,
.unlocked_ioctl = debug_card_ioctl,
};
static char *devnode(struct device *dev, umode_t *mode)
{
if (!mode)
return NULL;
if (dev->devt == MKDEV(chrdev_sys_major, 0) ||
dev->devt == MKDEV(chrdev_sys_major, 2))
*mode = 0666;
return NULL;
}
static int card_init_module(void)
{
dev_t dev = MKDEV(chrdev_sys_major, 0);
int alloc_ret = 0;
int cdev_ret = 0;
alloc_ret = alloc_chrdev_region(&dev, 0, num_of_dev, DRIVER_NAME);
if (alloc_ret) goto error;
chrdev_sys_major = MAJOR(dev);
cdev_init(&debug_card_cdev, &card_fops);
cdev_ret = cdev_add(&debug_card_cdev, dev, num_of_dev);
if (cdev_ret) goto error;
chrdev_sys_class = class_create(THIS_MODULE ,"debug_card_80port"); //Name to be displayed inside /sys/class/ when driver is loaded.
if (IS_ERR(chrdev_sys_class)) goto error;
chrdev_sys_class->devnode = devnode; //Set device file (/dev/debug_card_80port) permission to 0666 on creation
device_create(chrdev_sys_class, NULL, dev, NULL, "debug_card_80port"); //device file to be created under /dev.
printk(KERN_ALERT "%s driver(major: %d) installed.\n", DRIVER_NAME, chrdev_sys_major);
return 0;
error:
if (cdev_ret == 0) cdev_del(&debug_card_cdev);
if (alloc_ret == 0) unregister_chrdev_region(dev, num_of_dev);
return -1;
}
static void card_exit_module(void) {
dev_t dev = MKDEV(chrdev_sys_major, 0);
device_destroy(chrdev_sys_class, dev);
class_destroy(chrdev_sys_class);
cdev_del(&debug_card_cdev);
unregister_chrdev_region(dev, num_of_dev);
printk(KERN_ALERT "%s driver removed.\n", DRIVER_NAME);
}
module_init(card_init_module);
module_exit(card_exit_module);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("RayKuo's blog");
MODULE_INFO(intree, "Y");//fix err: "giodrv: loading out-of-tree module taints kernel."
# Makefile
KVERSION := $(shell uname -r)
obj-m := debug_card.o
all:
$(MAKE) -C /lib/modules/$(KVERSION)/build M=${PWD} modules
clean:
$(MAKE) -C /lib/modules/$(KVERSION)/build M=${PWD} clean
測試程式 sample code:
// test.c
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "../drv/debug_card.h"
int main(int argc, char *argv[])
{
int devfd;
unsigned int num = 0;
if (argc == 1) argv[1] = "0";
devfd = open("/dev/debug_card_80port", O_RDWR);
if (devfd == -1) {
printf("Can't open /dev/debug_card_80port\n");
return -1;
}
printf("Resetting debug card...\n");
ioctl(devfd, IOCTL_RESET, NULL);
printf("Done. Wait 1 second...\n");
sleep(1);
printf("Writing %s...\n", argv[1]);
write(devfd, argv[1], strlen(argv[1]));
printf("Done.\n");
close(devfd);
return 0;
}
# Makefile all: gcc test.c -o test clean: rm test
編譯與測試：
切到 debug_card driver 目錄，使用 make 指令 compiler：
cd debug_card/drv make
沒有錯誤的話可以得到 debug_card.ko (driver)。
使用 insmod 安裝 driver ：
$ sudo insmod debug_card.ko
看到 kernel 分配給 driver 的 major number。
# 查看 kernel 分配給 drive 的 major number $ cat /proc/devices|grep debug_card 243 debug_card # list 已載入的 driver $ lsmod|grep debug_card debug_card 16384 0 # driver 載入後建立的 class $ ls -dl /sys/class/debug* drwxr-xr-x 2 root root 0 10月 1 16:09 /sys/class/debug_card_80port # driver 載入後建立的 device node (不需使用 mknod 來手動建立)，用來與 user mode 程式溝通 $ ls -d /dev/debug* crw-rw-rw- 1 root root 243, 0 10月 1 16:09 /dev/debug_card_80port
到此為止，driver 與 device 已完成建置，test 測試程式將通過讀寫 device /dev/debug_card_80port (檔案)與 driver 溝通。
再來切到 test 測試程式目錄，使用 make 來 compiler 測試程式。
cd ../test make
執行 test 即可看到 debug card (80 port) 的變化。
# 往 80 port 丟 12h ./test 12
移除已安裝的 driver：
cd ../drv sudo rmmod debug_card.ko
Download source code : debug_card_src