centos man page for pci_request_region_exclusive

PCI_REQUEST_REGION_E(9) 					Hardware Interfaces					   PCI_REQUEST_REGION_E(9)

NAME
       pci_request_region_exclusive - Reserved PCI I/O and memory resource

SYNOPSIS
       int pci_request_region_exclusive(struct pci_dev * pdev, int bar, const char * res_name);

ARGUMENTS
       pdev
	   PCI device whose resources are to be reserved

       bar
	   BAR to be reserved

       res_name
	   Name to be associated with resource.

DESCRIPTION
       Mark the PCI region associated with PCI device pdev BR bar as being reserved by owner res_name. Do not access any address inside the PCI
       regions unless this call returns successfully.

       Returns 0 on success, or EBUSY on error. A warning message is also printed on failure.

       The key difference that _exclusive makes it that userspace is explicitly not allowed to map the resource via /dev/mem or sysfs.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						   PCI_REQUEST_REGION_E(9)