device number(dev_t)

device number(dev_t)

dev_t

description: 
    the dev_t type in is used to hold device numbers—both the major and minor

parts.

header: 
    #include

constructor: 
    MKDEV(int major, int minor);

method: 
    MAJOR(dev_t dev);    //obtain the major part of a dev_t 
    MINOR(dev_t dev);    //obtain the minor part of a dev_t 
    register_chrdev_region();    //manually obtain(register) device numbers

from the system 
    alloc_chrdev_region();        //allocate a major number  by kernel 
    unregister_chrdev_region();    //free the device number back to kernel

int print_dev_t(char *buffer, dev_t dev); //encode the device number into the given buffer; 
char *format_dev_t(char *buffer, dev_t dev); //encode the device number into the given buffer;