NAME

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

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #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).

DESCRIPTION

       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.

ERRORS

       EFAULT The address in mmio_addr is invalid.

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

       EINVAL Invalid length argument.

       ENODEV PCI support is not enabled.

       ENOMEM Insufficient memory.

VERSIONS

       These system calls are available since Linux 3.19.

STANDARDS

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

SEE ALSO

       syscall(2)