s390_pci_mmio_write, s390_pci_mmio_read — transfer data to/from PCI MMIO memory page


#include <asm/unistd.h>

int s390_pci_mmio_write(unsigned long mmio_addr,
                        void *user_buffer, size_t length);
int s390_pci_mmio_read(unsigned long mmio_addr,
                        void *user_buffer, size_t length);


The s390_pci_mmio_write() system call writes length bytes of data from the user-space buffer user_buffer to the PCI MMIO memory location specified by mmio_addr. The s390_pci_mmio_read() system call reads length bytes of data from the PCI MMIO memory location specified by mmio_addr to the user-space buffer user_buffer.

These system calls must be used instead of the simple assignment or data-transfer operations that are used to access the PCI MMIO memory areas mapped to user space on the Linux System z platform. The address specified by mmio_addr must belong to a PCI MMIO memory page mapping in the caller's address space, and the data being written or read must not cross a page boundary. The length value cannot be greater than the system page size.

Return Value

On success, s390_pci_mmio_write() and s390_pci_mmio_read() return 0. On error, -1 is returned and errno is set to one of the error codes listed below.



The address in mmio_addr is invalid.


user_buffer does not point to a valid location in the caller's address space.


Invalid length argument.


PCI support is not enabled.


Insufficient memory.


These system calls are available since Linux 3.19.

Conforming to

This Linux-specific system call is available only on the s390 architecture. The required PCI support is available beginning with System z EC12.


Glibc does not provide a wrapper for this system call, use syscall(2) to call it.

See Also



This page is part of release 5.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Referenced By


The man page s390_pci_mmio_read(2) is an alias of s390_pci_mmio_write(2).

2017-09-15 Linux Programmer's Manual