【Linux设备驱动】--0x03字符设备模块-完整的错误处理+全局数据结构放在同一结构体内

项目中经常会将所用到的所有全局数据结构放到同一个结构体内

struct simple_dev {
    dev_t  dev_no;
    struct cdev   cdev;
    struct class  *class;
    struct device *device;
};

该结构体将所用到的全局数据结构放在一起，这样可以在open的时候，将该指针放到file->private_data = dev;私有data字段内，方便其他系统调用接口使用

这里container_of无法操作内部嵌套的指针类型，所以struct cdev cdev;不能用作指针类型

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/slab.h>   // kfree,kmalloc
#include <linux/cdev.h>   // cdev_xxx
#include <linux/device.h> // device_xxx

struct simple_dev {
    dev_t  dev_no;
    struct cdev   cdev;
    struct class  *class;
    struct device *device;
};

struct simple_dev *g_simple_dev;

static int simple_cdev_open(struct inode *inode, struct file *file)
{
    struct simple_dev *dev;

    dev = container_of(inode->i_cdev, struct simple_dev, cdev);
    file->private_data = dev;

    return 0;
}

static int simple_cdev_release(struct inode *inode, struct file *file)
{
    struct simple_dev *dev;

    dev = file->private_data;

    return 0;
}

/* File operations struct for character device */
static const struct file_operations g_simple_dev_fops = {
    .owner   = THIS_MODULE,
    .open    = simple_cdev_open,
    .release = simple_cdev_release,
};

static int __init simple_cdev_init(void)
{
    int ret;

    g_simple_dev = kzalloc(sizeof(struct simple_dev), GFP_KERNEL);
    if (!g_simple_dev) {
        return -1;
    }

    ret = alloc_chrdev_region(&g_simple_dev->dev_no, 0, 1, "simple_cdev");
    if (!ret) {
        goto alloc_chrdev_failed;
    }

    cdev_init(&g_simple_dev->cdev, &g_simple_dev_fops);
    g_simple_dev->cdev.owner = THIS_MODULE;

    ret = cdev_add(&g_simple_dev->cdev, g_simple_dev->dev_no, 1);
    if (!ret) {
        goto cdev_add_failed;
    }

    g_simple_dev->class = class_create(THIS_MODULE, "simple_cdev");
    if (!g_simple_dev->class) {
        goto class_create_failed;
    }

    g_simple_dev->device = device_create(g_simple_dev->class, NULL, g_simple_dev->dev_no, NULL, "simple_cdev");
    if (!g_simple_dev->device) {
        goto device_create_failed;
    }
    
    return 0;

device_create_failed:
    class_destroy(g_simple_dev->class);
class_create_failed:
    cdev_del(&g_simple_dev->cdev);
cdev_add_failed:
    unregister_chrdev_region(g_simple_dev->dev_no, 1);
alloc_chrdev_failed:
    kfree(g_simple_dev);

    return -1;
}

static void __exit simple_cdev_exit(void)
{
    device_destroy(g_simple_dev->class, g_simple_dev->dev_no);
    class_destroy(g_simple_dev->class);
    cdev_del(&g_simple_dev->cdev);
    unregister_chrdev_region(g_simple_dev->dev_no, 1);
    kfree(g_simple_dev);
}

MODULE_LICENSE("GPL");
module_init(simple_cdev_init);
module_exit(simple_cdev_exit);