Linux驱动学习之内核接口和多节点设备

四盏灯：
原则上我们想要实现流水灯！
需要怎么做？
一个驱动 -> 生成一个设备文件！
一个设备文件怎么控制四个 LED 灯？
你有两种方法：
1 ：你写四个驱动你就能生成四个 LED 灯！
四个驱动有什么特点没
除了引脚不一样其他代码几乎都一样！
2 ：你写一个驱动却生成四个设备文件！

一驱多设

前置

open和relase参数一样，如果说多个设备用一套open，close，我们该怎么确定是哪个灯呢，我们可以想到stm32 hal库串口中断，通过回调函数参数的值，判断是哪个串口。

同理，对于多设备匹配一个open，我们可以也通过参数 inode-> r_dev 即通过设备号判断是那个设备。

由于inode结构体过于大，就只展示一小部分

驱动源码

cpp 复制代码

#include "linux/device.h"
#include "linux/export.h"
#include "linux/fs.h"
#include "linux/gpio.h"
#include "linux/mod_devicetable.h"
#include "linux/module.h"
#include "linux/of.h"
#include "linux/of_gpio.h"
#include "linux/platform_device.h"
#include "linux/cdev.h"
#include "linux/printk.h"
#include "linux/slab.h"



typedef struct g{
    uint32_t pin;
    char name[32];
    enum of_gpio_flags gpio_flag;
    struct g *next;
}GPIO;
GPIO head;
struct class * cls;
struct cdev * cdev;
static dev_t dev_num;
struct platform_device *node;
static int open (struct inode *inode, struct file *file)
{
    GPIO *p=&head;
    for(uint8_t i=0;i<of_gpio_named_count(node->dev.of_node,"led_pin");i++)
    {
        if(dev_num+i==inode->i_rdev)
        {
            gpio_set_value(p->next->pin,1);
        }
        p=p->next;
    }
    return 0;
}
static int close (struct inode *inode, struct file *file)
{
    GPIO *p=&head;
    for(uint8_t i=0;i<of_gpio_named_count(node->dev.of_node,"led_pin");i++)
    {
        if(dev_num+i==inode->i_rdev)
        {
            gpio_set_value(p->next->pin,0);
        }
        p=p->next;
    }
    return 0;
}
static struct file_operations fops={
    .owner=THIS_MODULE,
    .open=open,
    .release=close,

};
static	int probe(struct platform_device *d)
{
    node=d;
    head.next=NULL;
    printk("%d\r\n",of_gpio_named_count(d->dev.of_node,"led_pin"));
   for(int i=0;i<of_gpio_named_count(d->dev.of_node,"led_pin");i++)
   {
        GPIO *tem=kzalloc(sizeof(GPIO), GFP_KERNEL);
       tem->pin= of_get_named_gpio_flags(d->dev.of_node,"led_pin",i,&tem->gpio_flag);
        if(tem->gpio_flag==OF_GPIO_ACTIVE_LOW)
        {
            gpio_request(tem->pin,"led");
            gpio_direction_output(tem->pin,1);
        }
        else
        {
            gpio_request(tem->pin,"led");
            gpio_direction_output(tem->pin,0);
        }
        tem->next=head.next;
        head.next=tem;
        sprintf(tem->name,"led_%d",i);
   }
   printk("666\r\n");
    alloc_chrdev_region(&dev_num, 0,of_gpio_named_count(d->dev.of_node,"led_pin"), "led");
    cdev= cdev_alloc();
    cdev->ops=&fops;
    cdev_add(cdev,dev_num,of_gpio_named_count(d->dev.of_node,"led_pin"));
    cls= class_create(THIS_MODULE, "led");
    GPIO *p=&head;
    for(int i=0;i<of_gpio_named_count(d->dev.of_node,"led_pin");i++) {
    
        device_create(cls,NULL,dev_num+i,NULL,p->next->name);
        p=p->next;
    }
    return 0;
}
static	int remove(struct platform_device *d)
{
     
    printk(KERN_INFO "Goodbye, world!\n");
    return 0;
}

static struct of_device_id match={
    .compatible="led",
};
static struct platform_driver driver={
    .probe=probe,
    .remove=remove,
    .driver={
        .name="led",
        .of_match_table=&match,
    },
};

static int __init  start(void)
{
    platform_driver_register(&driver);
    printk("hahaha\r\n");
    return 0;
}
static void __exit stop(void)
{
    platform_driver_unregister(&driver);
    printk("gun\r\n");
}
module_init(start);
module_exit(stop);
MODULE_LICENSE("GPL");