cdev_init()函数

linux-2.6.22/include/linux/cdev.h

void cdev_init (struct cdev  *cdev,const struct file_operations *fops);

    @cdev: the structure to initialize
    @fops: the file_operations for this device
   
    Initializes cdev, remembering fops, making it ready to add to the system with cdev_add.

cdev_add() — add a char device to the system
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linux-2.6.22/include/linux/cdev.h

int cdev_add (struct cdev    * p,
              dev_t          dev,
              unsigned       count);

    @p: the cdev structure for the device
    @dev: the first device number for which this device is responsible
    @count: the number of consecutive minor numbers corresponding to this device
    cdev_add() adds the device represented by @p to the system, making it live immediately. A negative error code is returned on failure.

alloc_chrdev_region() — register a range of char device numbers
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linux-2.6.22/include/linux/cdev.h

int alloc_chrdev_region(dev_t            *dev,
                        unsigned int     baseminor,
                        unsigned int     count,
                        char             *name)

    @dev: output parameter for first assigned number
    @baseminor: first of the requested range of minor numbers(次设备号)
    @count: the number of minor numbers required
    @name: the name of the associated device or driver

    Allocates a range of char device numbers. The major number will be chosen dynamically, and returned (along with the first minor number) in dev. Returns zero or a negative error code.使用alloc_chrdev_region()函数动态获取主设备号。