Linux内核当中关于设备的管理

在linux内核当中，主要就是字符设备和块设备，对应的结构体就是struct cdev和struct gendisk，在内核当中是通过如下结构的两个变量bdev_map和cdev_map来进行管理的：

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1. struct kobj_map {
   
2.     struct probe {
   
3.         struct probe *next;
   
4.         dev_t dev;
   
5.         unsigned long range;
   
6.         struct module *owner;
   
7.         kobj_probe_t *get;
   
8.         int (*lock)(dev_t, void *);
   
9.         void *data;
   
10.     } *probes[255];
    
11.     struct mutex *lock;
    
12. };

它本质上就是一个带互斥量的哈希表，根据设备的主设备号%255来找到对应的槽，槽冲突使用链表的形式进行解决

• dev表示设备的设备号
• range表示辅设备号的范围
• owner表示拥有这个设备的模块
• get和kobject相关
• lock与设备锁定相关
• data则根据不同的map类型（字符或者块）分别指向不同的结构（cdev或者gendisk）

其中两个通用的设备结构的定义如下，其中gendisk稍微复杂一点，会涉及到分区等信息：

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1. struct cdev {
   
2.     struct kobject kobj;
   
3.     struct module *owner;
   
4.     const struct file_operations *ops;
   
5.     struct list_head list;
   
6.     dev_t dev;
   
7.     unsigned int count;
   
8. } __randomize_layout;

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1. struct gendisk {
   
2.     /* major, first_minor and minors are input parameters only,
   
3.      * don't use directly. Use disk_devt() and disk_max_parts().
   
4.      */
   
5.     int major;            /* major number of driver */
   
6.     int first_minor;
   
7.     int minors; /* maximum number of minors, =1 for
   
8.                                          * disks that can't be partitioned. */
   
9. 
   
10.     char disk_name[DISK_NAME_LEN];    /* name of major driver */
    
11.     char *(*devnode)(struct gendisk *gd, umode_t *mode);
    
12. 
    
13.     unsigned int events;        /* supported events */
    
14.     unsigned int async_events;    /* async events, subset of all */
    
15. 
    
16.     /* Array of pointers to partitions indexed by partno.
    
17.      * Protected with matching bdev lock but stat and other
    
18.      * non-critical accesses use RCU. Always access through
    
19.      * helpers.
    
20.      */
    
21.     struct disk_part_tbl __rcu *part_tbl;// 分区表
    
22.     struct hd_struct part0;
    
23. 
    
24.     const struct block_device_operations *fops;
    
25.     struct request_queue *queue;
    
26.     void *private_data;
    
27. 
    
28.     int flags;
    
29.     struct kobject *slave_dir;
    
30. 
    
31.     struct timer_rand_state *random;
    
32.     atomic_t sync_io;        /* RAID */
    
33.     struct disk_events *ev;
    
34. #ifdef CONFIG_BLK_DEV_INTEGRITY
    
35.     struct kobject integrity_kobj;
    
36. #endif    /* CONFIG_BLK_DEV_INTEGRITY */
    
37.     int node_id;
    
38.     struct badblocks *bb;
    
39. };

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1. struct kobj_map {
   
2.     struct probe {
   
3.         struct probe *next;
   
4.         dev_t dev;
   
5.         unsigned long range;
   
6.         struct module *owner;
   
7.         kobj_probe_t *get;
   
8.         int (*lock)(dev_t, void *);
   
9.         void *data;
   
10.     } *probes[255];
    
11.     struct mutex *lock;
    
12. };

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1. struct kobj_map {
   
2.     struct probe {
   
3.         struct probe *next;
   
4.         dev_t dev;
   
5.         unsigned long range;
   
6.         struct module *owner;
   
7.         kobj_probe_t *get;
   
8.         int (*lock)(dev_t, void *);
   
9.         void *data;
   
10.     } *probes[255];
    
11.     struct mutex *lock;
    
12. };