s390_pci_mmio_write man page

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


Referenced By


Explore man page connections for s390_pci_mmio_write(2).

s390_pci_mmio_read(2) is an alias of s390_pci_mmio_write(2).