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

#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.

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.

syscall(2)