s390_pci_mmio_write - Man Page

transfer data to/from PCI MMIO memory page


Standard C library (libc, -lc)


#include <sys/syscall.h>      /* Definition of SYS_* constants */
#include <unistd.h>

int syscall(SYS_s390_pci_mmio_write, unsigned long mmio_addr,
                       const void user_buffer[.length], size_t length);
int syscall(SYS_s390_pci_mmio_read, unsigned long mmio_addr,
                       void user_buffer[.length], size_t length);

Note: glibc provides no wrappers for these system calls, necessitating the use of syscall(2).


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 failure, -1 is returned and errno is set to indicate the error.



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.


Linux on s390.


Linux 3.19. System z EC12.

See Also


Referenced By


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

2023-10-31 Linux man-pages 6.06