实验目的
点亮龙芯开发板上面的用户自定义LED灯,编写LED驱动以及测试用例验证实现效果,LED位于开发板左下方(靠近USB口)第二个
原理图
LED通过电阻上拉至电源P3V3,低电平时LED被点亮
设备树
打开arch/loongarch/boot/dts/loongson/loongson_2k0300_pai_99.dts
,将72-150行的i2c0和i2c1两个节点注释掉,如下所示
将loongson_2k0300_pai_99设备树编译进内核,编译完后将内核scp到开发板的/boot
目录下,然后重启开发板
驱动示例
LED驱动
LED对应的GPIO号为83
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#define GPIOLED_CNT 1
#define GPIOLED_NAME "led"
#define OFF 0
#define ON 1
#define GPIO_LED 83
struct my_led_dev{
dev_t dev_id;
struct cdev cdev;
struct class *class;
struct device *device;
int major;
int minor;
struct device_node *nd;
int led;
};
struct my_led_dev led_dev;
static int led_open(struct inode *inode, struct file *filp)
{
filp->private_data = &led_dev;
return 0;
}
static ssize_t led_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)
{
return 0;
}
static ssize_t led_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{
int ret;
unsigned char data[1];
unsigned char ledstat;
struct my_led_dev *dev = filp->private_data;
ret = copy_from_user(data, buf, cnt);
if(ret < 0) {
printk("kernel write failed!\r\n");
return -EFAULT;
}
ledstat = data[0];
if(ledstat == ON) {
gpio_set_value(dev->led, 0);
} else if(ledstat == OFF) {
gpio_set_value(dev->led, 1);
}
return 0;
}
static int led_release(struct inode *inode, struct file *filp)
{
return 0;
}
static struct file_operations led_dev_fops = {
.owner = THIS_MODULE,
.open = led_open,
.read = led_read,
.write = led_write,
.release = led_release,
};
static int __init led_init(void)
{
int ret = 0;
led_dev.led = GPIO_LED;
if(led_dev.led < 0) {
printk("can't get led-gpio");
return -EINVAL;
}
ret = gpio_request(led_dev.led, "LED-GPIO");
if (ret) {
printk(KERN_ERR "led_dev: Failed to request led-gpio\n");
return ret;
}
ret = gpio_direction_output(led_dev.led, 1);
if(ret < 0) {
printk("can't set gpio!\r\n");
}
if (led_dev.major) {
led_dev.dev_id = MKDEV(led_dev.major, 0);
ret = register_chrdev_region(led_dev.dev_id, GPIOLED_CNT, GPIOLED_NAME);
if(ret < 0) {
pr_err("cannot register %s char driver [ret=%d]\n", GPIOLED_NAME, GPIOLED_CNT);
goto free_gpio;
}
} else {
ret = alloc_chrdev_region(&led_dev.dev_id, 0, GPIOLED_CNT, GPIOLED_NAME);
if(ret < 0) {
pr_err("%s Couldn't alloc_chrdev_region, ret=%d\r\n", GPIOLED_NAME, ret);
goto free_gpio;
}
led_dev.major = MAJOR(led_dev.dev_id);
led_dev.minor = MINOR(led_dev.dev_id);
}
led_dev.cdev.owner = THIS_MODULE;
cdev_init(&led_dev.cdev, &led_dev_fops);
cdev_add(&led_dev.cdev, led_dev.dev_id, GPIOLED_CNT);
if(ret < 0)
goto del_unregister;
led_dev.class = class_create(THIS_MODULE, GPIOLED_NAME);
if (IS_ERR(led_dev.class)) {
goto del_cdev;
}
led_dev.device = device_create(led_dev.class, NULL, led_dev.dev_id, NULL, GPIOLED_NAME);
if (IS_ERR(led_dev.device)) {
goto destroy_class;
}
return 0;
destroy_class:
class_destroy(led_dev.class);
del_cdev:
cdev_del(&led_dev.cdev);
del_unregister:
unregister_chrdev_region(led_dev.dev_id, GPIOLED_CNT);
free_gpio:
gpio_free(led_dev.led);
return -EIO;
}
static void __exit led_exit(void)
{
cdev_del(&led_dev.cdev);
unregister_chrdev_region(led_dev.dev_id, GPIOLED_CNT);
device_destroy(led_dev.class, led_dev.dev_id);
class_destroy(led_dev.class);
gpio_free(led_dev.led);
}
module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
Makefile
跟之前一篇文章的Makefile差不多,这里要改一下驱动名称
obj-m += led.o
KDIR:=/home/asensing/loongson/linux-4.19
ARCH=loongarch
CROSS_COMPILE=loongarch64-linux-gnu-
PWD?=$(shell pwd)
all:
make -C $(KDIR) M=$(PWD) modules
build脚本
分别编译测试用例和驱动模块
export PATH=$PATH:/home/asensing/loongson/loongson-gnu-toolchain-8.3-x86_64-loongarch64-linux-gnu-rc1.3-1/bin
make -j8
loongarch64-linux-gnu-gcc test.c -o test
FILE=$PWD/$(basename $PWD).ko
scp $FILE test root@192.168.137.128:/home/root
测试用例
c代码
#include "stdio.h"
#include "unistd.h"
#include "sys/types.h"
#include "sys/stat.h"
#include "fcntl.h"
#include "stdlib.h"
#include "string.h"
#include "time.h"
int main(int argc, char *argv[])
{
int fd, ret;
char *filename;
unsigned char data[1];
if(argc != 2){
printf("Error Usage!\r\n");
return -1;
}
filename = argv[1];
fd = open(filename, O_RDWR);
if(fd < 0){
printf("file %s open failed!\r\n", argv[1]);
return -1;
}
while(1) {
data[0] = 1;
ret = write(fd, data, sizeof(data));
if(ret < 0){
printf("LED Control Failed!\r\n");
close(fd);
return -1;
}
usleep(500000);
data[0] = 0;
ret = write(fd, data, sizeof(data));
if(ret < 0){
printf("LED Control Failed!\r\n");
close(fd);
return -1;
}
usleep(500000);
}
ret = close(fd);
if(ret < 0){
printf("file %s close failed!\r\n", argv[1]);
return -1;
}
return 0;
}
① 通过执行上面的build脚本,生成led.ko和test文件
② 插入内核驱动模块led.ko
③ 检查/dev目录是否已经生成设备节点
④ 执行test用例
命令行
在led.ko没有插入的情况下,也可以用以下脚本循环点亮LED灯
while true;
do
echo 1 > /sys/class/gpio/gpio48/value;
sleep 0.5;
echo 0 > /sys/class/gpio/gpio48/value;
sleep 0.5;
done;
实验效果
可以看到板子左下角第二颗LED被循环点亮