Module Timer

内核空间, 每5s打印一次计数值

//test_timer.c
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/timer.h>struct timer_list timer0;void timer0_callback(unsigned long data)
{static unsigned long cnt = 0;mod_timer(&timer0, jiffies + msecs_to_jiffies(5000));printk(KERN_INFO "timer0.data = %ld\n", cnt++);
}static int module_test_init(void)
{printk(KERN_ALERT "Module Timer Test\n");setup_timer(&timer0, timer0_callback, 0);mod_timer(&timer0, jiffies + msecs_to_jiffies(5000));return 0;
}static void module_test_exit(void)
{del_timer(&timer0);printk(KERN_ALERT "Goodbye Module Timer Test\n");
}module_init(module_test_init);
module_exit(module_test_exit);MODULE_AUTHOR("yiming");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Module Test");

其中:

• #include <linux/timer.h>, 定时器相关的头文件
• struct timer_list timer0;定义一个定时器
• setup_timer, 绑定定时器和回调函数
• mod_timer, 修改定时器的超时时间, 函数原型int mod_timer (struct timer_list * timer, unsigned long expires); 其中expires -- new timeout in jiffies, 而jiffies记录着从开机到现在的时钟中断次数(ticks), 和ms的转换关系用msecs_to_jiffies

然后是Makefile, 和上次hello例子中的Makefile基本一样, 除了第一行

obj-m:=test_timer.okernel_dir = /home/z/jetson/Linux_for_Tegra/source/public/kernel/kernel-4.9
cross_compile_dir = /home/z/jetson/l4t-gcc/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-makefile_dir := $(shell pwd)
top_makefile_dir := $(shell pwd)/top
build_dir := $(shell pwd)/buildall:@if [ ! -d ${top_makefile_dir} ]; then \export CROSS_COMPILE=${cross_compile_dir}; \export LOCALVERSION=-tegra; \mkdir -p ${top_makefile_dir}; \cd ${kernel_dir}; \make ARCH=arm64 O=${top_makefile_dir} tegra_defconfig; \cd ${top_makefile_dir}; \make ARCH=arm64 O=${top_makefile_dir} -j $$(nproc) modules_prepare; \echo "\n=================================\n"; \fi; \export CROSS_COMPILE=${cross_compile_dir}; \cd ${makefile_dir};\mkdir -p ${build_dir}; \make ARCH=arm64 -C ${top_makefile_dir} M=${makefile_dir} -j $$(nproc); \mv *.mod.c *.o *.order *.symvers ${build_dir}clean:@# rm -rf *.mod.* *.o *.order *.symvers *.korm -rf build *.ko top

其中:

• if..fi里面是看看有没有顶级Makefile, 没有就从内核源码中生成一个放到top文件夹里面

make, 然后拷贝生成的 test_timer.ko 到TX2, 测试

$ sudo insmod test_timer.ko# 可以看到大概5.1s打印一次
$ dmesg | tail -f
[12549.587808] Module Timer Test
[12554.685658] timer0.data = 0
[12559.805676] timer0.data = 1
[12564.925585] timer0.data = 2
[12570.045719] timer0.data = 3
[12575.165784] timer0.data = 4
[12580.285815] timer0.data = 5$ sudo rmmod test_timer 
$ dmesg | tail -f
[12790.207129] timer0.data = 46
[12795.195966] Goodbye Module Timer Test

Module GPIO

常见在用户空间中:

• export x > /sys/class/gpio/export, 使用sysfs接口将gpiox导入用户空间
• echo out > /sys/class/gpio/gpiox/direction, 设置gpiox为输出, in为输入
• echo 1 > /sys/class/gpio/gpiox/value, gpiox输出高电平
• cat /sys/class/gpio/gpiox/value, 读取gpiox电平

用户空间可以选用自己喜欢的语言Shell/C/C++/Python进行操作.

内核空间, 实现让GPIO396(官方载板J21 Pin7)每5s翻转一次电平, GPIO392(官方载板J21 Pin12)设置为上升沿+下降沿中断, 用杜邦线把两个GPIO连起来

//test_gpio.c
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/gpio.h>
#include <linux/interrupt.h> //参考下面的 GPIO Header Pinout 小节
static unsigned int gpiox = 396;
static unsigned int gpioy = 392;
static unsigned int irq_num;
struct timer_list timer0;static void timer0_callback(unsigned long data)
{static unsigned long cnt = 0;mod_timer(&timer0, jiffies + msecs_to_jiffies(5000));if(cnt % 2) {printk(KERN_INFO "gpio%d low\n", gpiox);gpio_set_value(gpiox, 0);} else {printk(KERN_INFO "gpio%d high\n", gpiox);gpio_set_value(gpiox, 1);}++cnt;
}static irq_handler_t gpioy_irq_callback(unsigned int irq, void *dev_id, struct pt_regs *regs)
{if(gpio_get_value(gpioy) == 1) {printk(KERN_INFO "rising irq\n");} else {printk(KERN_INFO "falling irq\n");}return (irq_handler_t) IRQ_HANDLED;
}static int module_test_init(void)
{int result = 0;printk(KERN_ALERT "Module GPIO Test\n");if(!gpio_is_valid(gpiox)) {printk(KERN_ALERT "GPIO Test: invalid gpio %d\n", gpiox);return -ENODEV;}//set gpiox outgpio_request(gpiox, "sysfs");gpio_direction_output(gpiox, true);gpio_set_value(gpiox, 0);gpio_export(gpiox, false);  //false: direction not change//set gpioy ingpio_request(gpioy, "sysfs");gpio_direction_input(gpioy);//gpio_set_debounce(gpioy, 200);  //Debounce 200msgpio_export(gpioy, false);//irqirq_num = gpio_to_irq(gpioy);printk("gpio%d is mapped to irq %d\n", gpioy, irq_num);result = request_irq(irq_num,(irq_handler_t)gpioy_irq_callback,IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,"test_gpio_handler",NULL);printk(KERN_INFO "GPIO_TEST: The interrupt request result is: %d\n", result);setup_timer(&timer0, timer0_callback, 0);mod_timer(&timer0, jiffies + msecs_to_jiffies(5000));return result;
}static void module_test_exit(void)
{gpio_set_value(gpiox, 0);gpio_unexport(gpiox);gpio_free(gpiox);free_irq(irq_num, NULL);gpio_unexport(gpioy);gpio_free(gpioy);del_timer(&timer0);printk(KERN_ALERT "Goodbye Module GPIO Test\n");
}module_init(module_test_init);
module_exit(module_test_exit);MODULE_AUTHOR("yiming");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Module Test");

其中:

• 包含了定时器的头文件timer.h, GPIO的gpio.h, 中断的interrupt.h
• gpiox设置为输出, 在定时器中断中每5s翻转一次电平
• gpioy设置为输入, 绑定到中断
• request_irq中的IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING指上升沿下降沿都中断, test_gpio_handler可以在/proc/interrupts中看到, 用于区分owner

Makefile还是上面的, 只需要第一行改为obj-m:=test_gpio.o

make后生成的test_gpio.ko拷贝到TX2, 记得用用杜邦线把官方载板上J21的Pin7和Pin12连起来, 测试

$ sudo insmod test_gpio.ko# 多了 gpio396 和 gpiochip392
$ ls /sys/class/gpio/
export   gpio396      gpiochip224  gpiochip256  unexport
gpio392  gpiochip216  gpiochip240  gpiochip320$ cat /proc/interrupts | grep test
205:         88          0          0          0          0          0  tegra-gpio  72 Edge      test_gpio_handler
$ sudo rmmod test_gpio.ko# dmesg | tail -f
$ dmesg -wH &
[1月24 16:04] Module GPIO Test
[  +0.003122] gpio392 is mapped to irq 205	# irq_num
[  +0.000021] GPIO_TEST: The interrupt request result is: 0	# 0 表示正常
[  +5.054777] gpio396 high	# gpio396初始设置为低电平, 5s后的这里变成高电平, 产生上升沿中断
[  +0.000494] rising irq
[  +5.119456] gpio396 low	# 5s后高电平变为低电平, 产生下降沿中断
[  +0.000059] falling irq
[  +5.120096] gpio396 high
[  +0.000490] rising irq
[  +5.119621] gpio396 low
[  +0.000322] falling irq
[  +5.119775] gpio396 high
[  +0.000395] rising irq
[  +5.119674] gpio396 low
[  +0.000338] falling irq
[ 1634.696580] Goodbye Module GPIO Test
[  +1.125281] Goodbye Module GPIO Test

这里测试J21的Pin12做输入中断是可以的, 但是Pin11做输入中断未成功, Pin15运行insmod直接重启, 啊这…

GPIO Header Pinout

之前的文章也写过一个C计算GPIO的工具 TX2/Xavier Linux GPIO 计算

NVIDIA Jetson TX2 J21 Header Pinout - JetsonHacks

Connector Pin #	Connector Label	HW GPIO	Linux GPIO	Notes
1	3V3
2	5V0
3	SDA1	EE.01	305	Don’t use as GPIO
4	5V0
5	SCL1	EE.00	304	Don’t use as GPIO
6	GND		0
7	GPIO_GCLK	J.04	396
8	TXD0	T.00	464	Don’t use as GPIO
9	GND		0
10	RXD0	T.01	465	Don’t use as GPIO
11	GPIO_GEN0	T.02	466
12	GPIO_GEN1	J.00	392
13	GPIO_GEN2	J.05	397
14	GND
15	GPIO_GEN3	P17	255
16	GPIO_GEN4	AA.00	296
17	3V3		0
18	GPIO_GEN5	Y.01	481
19	SPI_MOSI	N.05	429
20	GND		0
21	SPIO_MISO	N.04	428
22	GPIO_GEN6	P16	254
23	SPI_SCLK	N.03	427
24	SPI_CE0_N	N.06	430
25	GND
26	SPI_CE1_N
27	ID_SD	C.06	342	Don’t use as GPIO
28	ID_SC	C.05	341	Don’t use as GPIO
29	GPIO5	J.06	398
30	GND
31	GPIO6	AA.02	298
32	GPIO12	AA.01	297
33	GPIO13	I.05	389
34	GND
35	GPIO19	J.03	395
36	GPIO16	T.03	467
37	GPIO26	I.04	388
38	GPIO20	J.02	394
39	GND
40	GPIO21	J.01	393

Module chardev

直接把 lkmpg/chardev.c at master · sysprog21/lkmpg (github.com) 例子拿过来看

/* * chardev.c: Creates a read-only char device that says how many times * you have read from the dev file */ #include <linux/cdev.h> 
#include <linux/delay.h> 
#include <linux/device.h> 
#include <linux/fs.h> 
#include <linux/init.h> 
#include <linux/irq.h> 
#include <linux/kernel.h> 
#include <linux/module.h> 
#include <linux/poll.h> /*  Prototypes - this would normally go in a .h file */ 
static int device_open(struct inode *, struct file *); 
static int device_release(struct inode *, struct file *); 
static ssize_t device_read(struct file *, char __user *, size_t, loff_t *); 
static ssize_t device_write(struct file *, const char __user *, size_t, loff_t *); #define SUCCESS 0 
#define DEVICE_NAME "chardev" /* Dev name as it appears in /dev/   */ 
#define BUF_LEN 80 /* Max length of the message from the device */ /* Global variables are declared as static, so are global within the file. */ static int major; /* major number assigned to our device driver */ enum { CDEV_NOT_USED = 0, CDEV_EXCLUSIVE_OPEN = 1, 
}; /* Is device open? Used to prevent multiple access to device */ 
static atomic_t already_open = ATOMIC_INIT(CDEV_NOT_USED); static char msg[BUF_LEN]; /* The msg the device will give when asked */ static struct class *cls; static struct file_operations chardev_fops = { .read = device_read, .write = device_write, .open = device_open, .release = device_release, 
}; static int __init chardev_init(void) 
{ major = register_chrdev(0, DEVICE_NAME, &chardev_fops); if (major < 0) { pr_alert("Registering char device failed with %d\n", major); return major; } pr_info("I was assigned major number %d.\n", major); cls = class_create(THIS_MODULE, DEVICE_NAME); device_create(cls, NULL, MKDEV(major, 0), NULL, DEVICE_NAME); pr_info("Device created on /dev/%s\n", DEVICE_NAME); return SUCCESS; 
} static void __exit chardev_exit(void) 
{ device_destroy(cls, MKDEV(major, 0)); class_destroy(cls); /* Unregister the device */ unregister_chrdev(major, DEVICE_NAME); 
} /* Methods */ /* Called when a process tries to open the device file, like * "sudo cat /dev/chardev" */ 
static int device_open(struct inode *inode, struct file *file) 
{ static int counter = 0; if (atomic_cmpxchg(&already_open, CDEV_NOT_USED, CDEV_EXCLUSIVE_OPEN)) return -EBUSY; sprintf(msg, "I already told you %d times Hello world!\n", counter++); try_module_get(THIS_MODULE); return SUCCESS; 
} /* Called when a process closes the device file. */ 
static int device_release(struct inode *inode, struct file *file) 
{ /* We're now ready for our next caller */ atomic_set(&already_open, CDEV_NOT_USED); /* Decrement the usage count, or else once you opened the file, you will * never get get rid of the module. */ module_put(THIS_MODULE); return SUCCESS; 
} /* Called when a process, which already opened the dev file, attempts to * read from it. */ 
static ssize_t device_read(struct file *filp, /* see include/linux/fs.h   */ char __user *buffer, /* buffer to fill with data */ size_t length, /* length of the buffer     */ loff_t *offset) 
{ /* Number of bytes actually written to the buffer */ int bytes_read = 0; const char *msg_ptr = msg; if (!*(msg_ptr + *offset)) { /* we are at the end of message */ *offset = 0; /* reset the offset */ return 0; /* signify end of file */ } msg_ptr += *offset; /* Actually put the data into the buffer */ while (length && *msg_ptr) { /* The buffer is in the user data segment, not the kernel * segment so "*" assignment won't work.  We have to use * put_user which copies data from the kernel data segment to * the user data segment. */ put_user(*(msg_ptr++), buffer++); length--; bytes_read++; } *offset += bytes_read; /* Most read functions return the number of bytes put into the buffer. */ return bytes_read; 
} /* Called when a process writes to dev file: echo "hi" > /dev/chardev */ 
static ssize_t device_write(struct file *filp, const char __user *buff, size_t len, loff_t *off) 
{ pr_alert("Sorry, this operation is not supported.\n"); return -EINVAL; 
} module_init(chardev_init); 
module_exit(chardev_exit); MODULE_LICENSE("GPL");

其中:

• #define DEVICE_NAME "chardev", 那insmod后对应的设备就是 /dev/chardev
• struct file_operations 采用分配给结构的新方法read write open release, 用C99的点语法来指定初始值设定项.
• chardev_init中, 用major 0 传递给 register_chrdev, 动态分配major numer
• atomic_cmpxchg(&already_open, CDEV_NOT_USED, CDEV_EXCLUSIVE_OPEN) 是原子判断, 当 already_open的值为CDEV_NOT_USED, 也就是未使用时, 赋值为CDEV_NOT_USED + CDEV_EXCLUSIVE_OPEN, 也就是打开, 返回值为旧值, 也就是 CDEV_NOT_USED=0
• MKDEV(major, 0), 将主设备号和次设备号转换为dev_t类型
• put_user(*(msg_ptr++), buffer++); 把内核空间的数据msg拷贝到用户空间buffer

make后生成的test_chardev.ko拷贝到TX2, 测试

$ sudo insmod test_chardev.ko 
$ sudo dmesg | tail -2
[ 9657.474056] I was assigned major number 506.
[ 9657.474379] Device created on /dev/chardev# open read
$ sudo cat /dev/chardev
I already told you 0 times Hello world!
$ sudo cat /dev/chardev
I already told you 1 times Hello world!# write
$ sudo sh -c 'echo "hi" > /dev/chardev'
sh: echo: I/O error
$ dmesg | tail -f
[   89.636842] Sorry, this operation is not supported.$ sudo rmmod test_chardev

备忘

块设备block -> b, 字符设备character -> c, 链接link -> l, 文件夹directory - d

$ ls -l /dev
...
crw-rw----  1 root i2c      89,   0 1月  24 15:37 i2c-0
crw-rw----  1 root i2c      89,   1 1月  24 15:37 i2c-1
lrwxrwxrwx  1 root root          25 1月  24 15:37 initctl -> /run/systemd/initctl/fifo
drwxr-xr-x  4 root root         220 1月  24 15:37 input
brw-rw----  1 root disk    179,   0 1月  24 15:37 mmcblk0
drwxrwxrwt  2 root root          60 1月  24 15:37 shm
crw-rw----  1 root dialout   4,  67 1月  24 15:37 ttyS3
crw-rw----  1 root dialout   4, 143 1月  24 15:37 ttyTCU0
crw-rw----  1 root dialout 238,   1 1月  24 15:37 ttyTHS1
crw-rw----  1 root dialout 238,   2 1月  24 15:37 ttyTHS2
crw-rw----  1 root dialout 238,   3 1月  24 15:37 ttyTHS3# 参考 
# https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/Documentation/admin-guide/devices.txt
# https://sysprog21.github.io/lkmpg/
# i2c-0, i2c-1 的89是major, 主设备号, 它们由同一驱动程序(major 8)处理
# i2c-0 的0 是minor, 次设备号 # cat /proc/devices

参考

• Linux内核中的jiffies及其作用介绍及jiffies等相关函数详解 - 专注it - 博客园 (cnblogs.com)
• NVIDIA Tegra186 GPIO controllers
• Writing a Linux Loadable Kernel Module (LKM) - Interfacing to GPIOs | derekmolloy.ie
• sysprog21/lkmpg: The Linux Kernel Module Programming Guide (updated for 5.x kernels) (github.com)
• devices.txt « admin-guide « Documentation - kernel/git/stable/linux.git - Linux kernel stable tree
• atomic_cmpxchg_gangdai的博客-CSDN博客_atomic_cmpxchg
• MKDEV宏定义及其主要函数_m0_37141848的博客-CSDN博客_mkdev函数

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