本文主要是介绍【驱动篇】龙芯LS2K0300之LED驱动，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
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i2c1和i2c2两个节点注释掉，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 83struct 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
龙芯LS2K0300之LED驱动
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