本节是关于生成设备节点。
学习资料来源于迅为的视频学习教程的整理
1. 杂项设备，或者说是对一部分字符设备的封装或者一部分不好分类的。
可以节省主设备号，驱动写起来相对简单（用封装好的杂项设备可以减少一步注册主设备号的过程）
2.源代码位置
杂项设备初始化源代码：/drivers/char/misc.c，属于内核中强制编译的。
杂项设备注册头文件：include/linux/miscdevice.h，主要的结构体为miscdevice
1 struct miscdevice { 2 int minor; //设备号，一般系统分配随机取值 3 const char *name; //生成设备节点的名称，无限制 4 const struct file_operations *fops; //指向一个设备节点文件，对文件的操作 5 struct list_head list; 6 struct device *parent; 7 struct device *this_device; 8 const char *nodename; 9 mode_t mode; 10 }; 11 12 extern int misc_register(struct miscdevice * misc); //生成设备节点的函数 13 extern int misc_deregister(struct miscdevice *misc);
设备节点本质是文件一个特殊文件，包括文件名，打开关闭等，文件结构体的头文件为include/linux/fs.h，结构体为file_operations
1 //相当重要的结构体 2 /* These macros are for out of kernel modules to test that 3 * the kernel supports the unlocked_ioctl and compat_ioctl 4 * fields in struct file_operations. */ 5 #define HAVE_COMPAT_IOCTL 1 6 #define HAVE_UNLOCKED_IOCTL 1 7 8 /* 9 * NOTE: 10 * all file operations except setlease can be called without 11 * the big kernel lock held in all filesystems. 12 */ 13 struct file_operations { 14 struct module *owner; 15 loff_t (*llseek) (struct file *, loff_t, int); 16 ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); 17 ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); 18 ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t); 19 ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t); 20 int (*readdir) (struct file *, void *, filldir_t); 21 unsigned int (*poll) (struct file *, struct poll_table_struct *); 22 /* remove by cym 20130408 support for MT660.ko */ 23 #if 0 24 //#ifdef CONFIG_SMM6260_MODEM 25 #if 1// liang, Pixtree also need to use ioctl interface... 26 int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long); 27 #endif 28 #endif 29 /* end remove */ 30 long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); 31 long (*compat_ioctl) (struct file *, unsigned int, unsigned long); 32 int (*mmap) (struct file *, struct vm_area_struct *); 33 int (*open) (struct inode *, struct file *); 34 int (*flush) (struct file *, fl_owner_t id); 35 int (*release) (struct inode *, struct file *); 36 int (*fsync) (struct file *, int datasync); 37 int (*aio_fsync) (struct kiocb *, int datasync); 38 int (*fasync) (int, struct file *, int); 39 int (*lock) (struct file *, int, struct file_lock *); 40 ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int); 41 unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); 42 int (*check_flags)(int); 43 int (*flock) (struct file *, int, struct file_lock *); 44 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int); 45 ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int); 46 int (*setlease)(struct file *, long, struct file_lock **); 47 long (*fallocate)(struct file *file, int mode, loff_t offset, 48 loff_t len); 49 /* add by cym 20130408 support for MT6260 and Pixtree */ 50 #if defined(CONFIG_SMM6260_MODEM) || defined(CONFIG_USE_GPIO_AS_I2C) 51 int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long); 52 #endif 53 /* end add */ 54 };