Connection between linux characters cdev and inode

Article Title: connection between linux characters cdev and inode. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

I haven't read much for a long time. Recently I reviewed the driver part of the character device and wrote a note.

Char Device Driver

Related Data Structure:

Struct cdev {

Struct kobject kobj;

Struct module * owner;

Const struct file_operations * ops;

Struct list_head list;

Dev_t dev;

Unsigned int count;

};

Struct kobj_map {

Struct probe {

Struct probe * next;

Dev_t dev;

Unsigned long range;

Struct module * owner;

Kobj_probe_t * get;

Int (* lock) (dev_t, void *);

Void * data;

} * Probes [255];

Struct mutex * lock;

};

Static struct char_device_struct {

Struct char_device_struct * next;

Unsigned int major;

Unsigned int baseminor;

Int minorct;

Char name [64];

Struct file_operations * fops;

Struct cdev * cdev;/* will die */

} * Chrdevs [CHRDEV_MAJOR_HASH_SIZE];

# Define CHRDEV_MAJOR_HASH_SIZE 255

The following article describes the character device driver in three aspects and their association:

1. Character-driven model

2. device Number of the character device

3. Access to character device files in the file system

1. Character-driven model

Each character driver is represented by a cdev structure.

In the device driver model, the kobject mapping domain is used to record the device driver.

This is represented by the struct kobj_map structure. It is embedded with an array of 255 struct probe pointers.

Kobj_map is referenced by the global variable cdev_map: static struct kobj_map * cdev_map;

Function Description:

Cdev_alloc () is used to create a cdev object.

Cdev_add () is used to add the cdev object to the driver model. It is implemented through kobj_map.

Kobj_map () creates a probe object, inserts it into an item in cdev_map, and associates probe-> data with cdev

Struct kobject * kobj_lookup (struct kobj_map * domain, dev_t dev, int * index)

Search for the built-in kobject. (probe-> data-> kobj) of the cdev object in cdev_map Based on the device number, and return the kobject of cdev.

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