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.
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.
These system calls are available since Linux 3.19.
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.
This page is part of release 4.10 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/.
s390_pci_mmio_read(2) is an alias of s390_pci_mmio_write(2).