Man page 9 : alloc_chrdev_region

alloc_chrdev_region - register a range of char device numbers

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

dev
    output parameter for first assigned number

baseminor
    first of the requested range of minor numbers

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.