2.Linux按键驱动-创建字符设备，通过应用程序读取按键值
1.在上一个博客的基础上，添加一个字符设备
https://blog.csdn.net/weixin_40933496/article/details/143253515?spm=1001.2014.3001.5501
2.在probe函数中注册字符设备
register_chrdev(包含对应的file_operations结构体)
class_create
device_create
3.在中断处理函数中唤醒等待队列，然后在read函数中返回按键值。
3.实现的代码
3.1驱动程序
#include <linux/irqreturn.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
#include <linux/gpio/consumer.h>
#include <linux/platform_device.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/slab.h>
/* 定义结构体来描述gpio */
struct gpio_key{
int gpio;
struct gpio_desc* gpiod;
int flag;
int irq;
};
/* 定义全局变量来存储设备树中的所有gpio节点信息 */
static struct gpio_key* gpio_keys_100ask;
/* 字符设备的主设备号 */
static unsigned int major = 0;
static struct class *gpio_class;
static int g_key = 0;
/* 定义等待队列 */
static DECLARE_WAIT_QUEUE_HEAD(gpio_key_wait);
static ssize_t gpio_read(struct file *fp, char __user *buf, size_t size, loff_t * offset)
{
int err;
wait_event_interruptible(gpio_key_wait, g_key);
err = copy_to_user(buf, &g_key, 4);
g_key = 0;
return 4;
}
static const struct file_operations gpio_fops = {
.owner = THIS_MODULE,
.read = gpio_read,
};
static irqreturn_t gpio_key_isr(int irq, void *dev_id)
{
struct gpio_key* gpio_key = dev_id;
int val;
val = gpio_get_value(gpio_key->gpio);
//printk("key %d %d\n", gpio_key->gpio, val);
g_key = (gpio_key->gpio << 8) | val;
wake_up_interruptible(&gpio_key_wait);
return IRQ_HANDLED;
}
static int gpio_probe(struct platform_device *pdev)
{
int count, i;
struct device_node *node;
int err;
node = pdev->dev.of_node;
count = of_gpio_count(node);
if (!count)
{
printk("%s %s line %d, there isn't any gpio available\n", __FILE__, __FUNCTION__, __LINE__);
return -1;
}
/* 申请资源 */
gpio_keys_100ask = kzalloc(sizeof(struct gpio_key) * count, GFP_KERNEL);
if (!gpio_keys_100ask)
{
printk("kzalloc error\n");
return -1;
}
/* 获得资源 */
for (i = 0; i < count; i++)
{
gpio_keys_100ask[i].gpio = of_get_gpio(node, i);
if (gpio_keys_100ask[i].gpio < 0)
{
printk("%s %s line %d, of_get_gpio_flags fail\n", __FILE__, __FUNCTION__, __LINE__);
return -1;
}
gpio_keys_100ask[i].gpiod = gpio_to_desc(gpio_keys_100ask[i].gpio);
gpio_keys_100ask[i].irq = gpio_to_irq(gpio_keys_100ask[i].gpio);
/* 申请中断 */
err = request_irq(gpio_keys_100ask[i].irq, gpio_key_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, "test1_gpio_keys_100ask", &gpio_keys_100ask[i]);
if (err)
{
printk("request_irq err\n");
}
}
/* 注册字符设备 */
major = register_chrdev(major, "100ask_key", &gpio_fops);
if(major < 0)
{
printk("register_chrdev err'\n");
return -1;
}
/* 注册类 */
gpio_class = class_create(THIS_MODULE, "100ask_key_class");
/* 注册设备 */
device_create(gpio_class, NULL, MKDEV(major,0), NULL, "100ask_key_button");
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
return 0;
}
static int gpio_remove(struct platform_device *pdev)
{
int count, i;
struct device_node *node;
node = pdev->dev.of_node;
count = of_gpio_count(node);
device_destroy(gpio_class, MKDEV(major,0));
class_destroy(gpio_class);
unregister_chrdev(major, "100ask_key");
for (i = 0; i < count; i++)
{
free_irq(gpio_keys_100ask[i].irq, &gpio_keys_100ask[i]);
}
kfree(gpio_keys_100ask);
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
return 0;
}
/*
* 在设备树中添加的节点的compatible属性为："test1_100ask,test1_gpio_key"
*/
static const struct of_device_id gpio_key_of_match[] = {
{.compatible = "test1_100ask,test1_gpio_key"},
{/* 这里必须要有一个空项，表示结束 */}
};
static struct platform_driver gpio_driver = {
.driver = {
.name = "test1_gpio_keys_100ask",
.of_match_table = gpio_key_of_match,
},
.probe = gpio_probe,
.remove = gpio_remove,
};
/* 基于platform总线来实现这个程序 */
static int gpio_init(void)
{
int ret;
ret = platform_driver_register(&gpio_driver);
if (ret != 0)
{
printk("platform_driver_register err\n");
return -1;
}
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
return ret;
}
static void gpio_exit(void)
{
platform_driver_unregister(&gpio_driver);
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
}
module_init(gpio_init);
module_exit(gpio_exit);
MODULE_LICENSE("GPL");
3.2应用程序
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, char** argv)
{
int fd;
int val;
int num;
/* 判断输入值是否合法 */
if(argc != 2)
{
printf("Usage ./button_app /dev/devname\n");
return -1;
}
fd = open(argv[1], O_RDONLY);
if (fd == -1)
{
printf("open err\n");
}
while(1)
{
read(fd, &val, 4);
num = val >>8;
printf("get button: %x val = %x\n", num, val - num *(1 << 8));
}
close(fd);
return 0;
}
3.3Makefile文件
KERN_DIR = /home/book/100ask_imx6ull-sdk/Linux-4.9.88
all:
make -C $(KERN_DIR) M=`pwd` modules
$(CROSS_COMPILE)gcc -o button_app button_app.c
clean:
make -C $(KERN_DIR) M=`pwd` modules clean
rm -rf modules.order
rm -rf button_app
obj-m += button_drv.o
3.4运行方式
4.实现方式
4.1 gpio_probe中添加字符设备代码
4.2 gpio_remove函数中添加对应的删除代码
4.3 定义全局变量，等待队列
4.4在中断服务程序中，给全局变量赋值，并且唤醒等待队列
4.5此时，.read函数会将数据拷贝回用户空间
5.文件路径
/home/book/nfs_rootfs/CSDN/01_gpio_irq/02_read_key_irq