最小可运行示例
从其他答案中最小化。使用GitHub upstream进行测试设置。
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#define NAME "lkmc_character_device_create"
static int major = -1;
static struct cdev mycdev;
static struct class *myclass = NULL;
static int show(struct seq_file *m, void *v)
{
seq_printf(m, "abcd");
return 0;
}
static int open(struct inode *inode, struct file *file)
{
return single_open(file, show, NULL);
}
static const struct file_operations fops = {
.llseek = seq_lseek,
.open = open,
.owner = THIS_MODULE,
.read = seq_read,
.release = single_release,
};
static void cleanup(int device_created)
{
if (device_created) {
device_destroy(myclass, major);
cdev_del(&mycdev);
}
if (myclass)
class_destroy(myclass);
if (major != -1)
unregister_chrdev_region(major, 1);
}
static int myinit(void)
{
int device_created = 0;
if (alloc_chrdev_region(&major, 0, 1, NAME "_proc") < 0)
goto error;
if ((myclass = class_create(THIS_MODULE, NAME "_sys")) == NULL)
goto error;
if (device_create(myclass, NULL, major, NULL, NAME "_dev") == NULL)
goto error;
device_created = 1;
cdev_init(&mycdev, &fops);
if (cdev_add(&mycdev, major, 1) == -1)
goto error;
return 0;
error:
cleanup(device_created);
return -1;
}
static void myexit(void)
{
cleanup(1);
}
module_init(myinit)
module_exit(myexit)
MODULE_LICENSE("GPL");
device_destroy
(它也负责删除设备节点),cdev_del
从内核中注销设备。在删除每个设备之后,调用class_destroy
删除类,然后 - 调用unregister_chrdev_region
。创建设备时所做的操作按通常的顺序相反地撤消。 - Eugenecdev_add()
之后调用device_create()
。cdev_add()
准备内核结构以维护设备,而device_create()
使设备可用于用户空间等其他操作。一旦您将设备提供给用户空间,该设备就应该准备好处理来自那里的请求。 - Eugene