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alloc_chrdev_region(9) [centos man page]

ALLOC_CHRDEV_REGION(9)						   Char devices 					    ALLOC_CHRDEV_REGION(9)

alloc_chrdev_region - register a range of char device numbers SYNOPSIS
int alloc_chrdev_region(dev_t * dev, unsigned baseminor, unsigned count, const char * name); ARGUMENTS
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 DESCRIPTION
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. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 ALLOC_CHRDEV_REGION(9)

Check Out this Related Man Page

MAKEDEV(3)						   BSD Library Functions Manual 						MAKEDEV(3)

makedev, major, minor -- device number conversion SYNOPSIS
#include <sys/types.h> dev_t makedev(int major, int minor); int major(dev_t dev); int minor(dev_t dev); DESCRIPTION
The makedev() macro allows a unique device number to be generated based on its major and minor number. The major() and minor() macros can be used to obtain the original numbers from the device number dev. In previous implementations of FreeBSD all block and character devices were uniquely identified by a pair of major and minor numbers. The major number referred to a certain device class (e.g. disks, TTYs) while the minor number identified an instance within the device class. Later versions of FreeBSD automatically generate a unique device number for each character device visible in /dev/. These numbers are not divided in device classes. On FreeBSD these macros are only used by utilities that need to exchange numbers with other operating systems that may use different encod- ings for dev_t, but also applications that present these numbers to the user in a more conventional way. RETURN VALUES
The major() macro returns a device major number that has a value between 0 and 255. The minor() macro returns a device minor number whose value can span the complete range of an int. SEE ALSO
mknod(2), devname(3), devfs(5) BSD
September 28, 2008 BSD
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