162 lines
4.4 KiB
C
162 lines
4.4 KiB
C
/**
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* @file demo_misc.c
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* @author Rick Chan (cy187lion@sina.com)
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* @brief Linux misc driver demo.
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在 Linux 驱动中，会把一些无法归类的设备定义为混杂设备，它们是拥
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有着共同的特性的简单字符设备。它们的特点是共享统一的主设备号 10，
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但每个设备可以选择一个单独的次设备号。
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通常情况下，一个字符设备都不得不在初始化的过程中进行下面的步骤：
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1.通过alloc_chrdev_region()分配主/次设备号
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2.使用cdev_init()和cdev_add()来以一个字符设备注册自己
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而一个misc驱动，则可以只用一个调用misc_register()来完成这所有
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的步骤。
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所有的 miscdevice 设备形成一个链表，对设备访问时，内核根据次设
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备号查找对应的 miscdevice 设备，然后调用其 file_operations
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中注册的文件操作方法进行操作。
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* @version 0.1.1
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* @date 2020-04-27
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*
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* @copyright Copyright (c) 2020
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*
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/miscdevice.h>
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#include <linux/uaccess.h>
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MODULE_AUTHOR("Rick Chan");
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MODULE_LICENSE("GPL");
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#define DEMO_MAGIC 'R'
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#define DEMO_IOC_SIZE 8
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#define DEMO_CTL_IOC _IOC(_IOC_READ|_IOC_WRITE, DEMO_MAGIC, 0, DEMO_IOC_SIZE)
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#define DEMO_CTL_IO _IO(DEMO_MAGIC, 1)
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#define DEMO_CTL_IOR _IOR(DEMO_MAGIC, 2, uint16_t)
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#define DEMO_CTL_IOW _IOW(DEMO_MAGIC, 3, int32_t)
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#define DEMO_CTL_IOWR _IOWR(DEMO_MAGIC, 4, uint32_t)
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#define DEMO_CTL_MAX 5
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static int demo_open(struct inode *inode, struct file* filp)
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{
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return 0;
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}
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static int demo_release(struct inode *inode, struct file* filp)
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{
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return 0;
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}
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static loff_t demo_llseek(struct file *filp, loff_t offset, int origin)
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{
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return filp->f_pos;
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}
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static ssize_t demo_read(struct file *filp, char __user *buffer, size_t count, loff_t *offset)
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{
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const char __user *p = buffer;
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return p-buffer;
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}
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static ssize_t demo_write(struct file *filp, const char __user *buffer, size_t count, loff_t *offset)
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{
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const char __user *p = buffer;
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return p-buffer;
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}
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static long demo_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
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{
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static int err = 0;
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// 检测 cmd 合法性.
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if(DEMO_MAGIC!=_IOC_TYPE(cmd))
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return -EINVAL;
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if(DEMO_CTL_MAX<_IOC_NR(cmd))
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return -EINVAL;
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// 根据命令类型, 检测参数空间是否可以访问.
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if(_IOC_DIR(cmd)&_IOC_READ)
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err = !access_ok(VERIFY_WRITE, (void *)arg, _IOC_SIZE(cmd));
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else if(_IOC_DIR(cmd)&_IOC_WRITE)
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err = !access_ok(VERIFY_READ, (void *)arg, _IOC_SIZE(cmd));
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if (err)
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return -EFAULT;
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// 根据命令, 来选择执行哪个分支.
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switch(cmd)
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{
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case DEMO_CTL_IOC:
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{
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uint8_t tmp[DEMO_IOC_SIZE];
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copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
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copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
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}
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break;
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case DEMO_CTL_IO:
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break;
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case DEMO_CTL_IOR:
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{
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uint16_t tmp = 0x55AA;
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copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
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}
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break;
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case DEMO_CTL_IOW:
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{
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int32_t tmp = 0;
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copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
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}
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break;
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case DEMO_CTL_IOWR:
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{
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uint32_t tmp = 0;
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copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
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copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
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}
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break;
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default:
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return -ENOIOCTLCMD;
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}
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return 0;
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}
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static int demo_mmap(struct file* filp, struct vm_area_struct* vma)
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{
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return 0;
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}
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static struct file_operations demo_fops = {
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.owner = THIS_MODULE,
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.open = demo_open,
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.release = demo_release,
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.llseek = demo_llseek,
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.read = demo_read,
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.write = demo_write,
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.unlocked_ioctl = demo_ioctl,
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.mmap = demo_mmap
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};
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static struct miscdevice demo_dev = {
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.minor = MISC_DYNAMIC_MINOR, // Dynamically allocate minor.
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.name = "demo_misc",
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.fops = &demo_fops,
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};
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static int __init demo_init(void)
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{
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misc_register(&demo_dev); // 注册混杂设备驱动.
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return 0;
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}
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static void __exit demo_exit(void)
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{
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misc_deregister(&demo_dev); // 撤销混杂设备驱动.
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}
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module_init(demo_init);
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module_exit(demo_exit);
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