man2/s390_pci_mmio_write.2

   1 .\" Copyright (c) IBM Corp. 2015
   2 .\" Author: Alexey Ishchuk <aishchuk@linux.vnet.ibm.com>
   3 .\"
   4 .\" SPDX-License-Identifier: GPL-2.0-or-later
   5 .\"
   6 .TH S390_PCI_MMIO_WRITE 2 2021-03-22 "Linux Programmer's Manual"
   7 .SH NAME
   8 s390_pci_mmio_write, s390_pci_mmio_read \- transfer data to/from PCI
   9 MMIO memory page
  10 .SH LIBRARY
  11 Standard C library
  12 .RI ( libc ", " \-lc )
  13 .SH SYNOPSIS
  14 .nf
  15 .BR "#include <sys/syscall.h>" "      /* Definition of " SYS_* " constants */"
  16 .B #include <unistd.h>
  17 .PP
  18 .BI "int syscall(SYS_s390_pci_mmio_write, unsigned long " mmio_addr ,
  19 .BI "                       const void *" user_buffer ", size_t " length );
  20 .BI "int syscall(SYS_s390_pci_mmio_read, unsigned long " mmio_addr ,
  21 .BI "                       void *" user_buffer ", size_t " length );
  22 .fi
  23 .PP
  24 .IR Note :
  25 glibc provides no wrappers for these system calls,
  26 necessitating the use of
  27 .BR syscall (2).
  28 .SH DESCRIPTION
  29 The
  30 .BR s390_pci_mmio_write ()
  31 system call writes
  32 .IR length
  33 bytes of data from the user-space buffer
  34 .IR user_buffer
  35 to the PCI MMIO memory location specified by
  36 .IR mmio_addr .
  37 The
  38 .BR s390_pci_mmio_read ()
  39 system call reads
  40 .I length
  41 bytes of
  42 data from the PCI MMIO memory location specified by
  43 .IR mmio_addr
  44 to the user-space buffer
  45 .IR user_buffer .
  46 .PP
  47 These system calls must be used instead of the simple assignment
  48 or data-transfer operations that are used to access the PCI MMIO
  49 memory areas mapped to user space on the Linux System z platform.
  50 The address specified by
  51 .IR mmio_addr
  52 must belong to a PCI MMIO memory page mapping in the caller's address space,
  53 and the data being written or read must not cross a page boundary.
  54 The
  55 .IR length
  56 value cannot be greater than the system page size.
  57 .SH RETURN VALUE
  58 On success,
  59 .BR s390_pci_mmio_write ()
  60 and
  61 .BR s390_pci_mmio_read ()
  62 return 0.
  63 On failure, \-1 is returned and
  64 .IR errno
  65 is set to indicate the error.
  66 .SH ERRORS
  67 .TP
  68 .B EFAULT
  69 The address in
  70 .I mmio_addr
  71 is invalid.
  72 .TP
  73 .B EFAULT
  74 .IR user_buffer
  75 does not point to a valid location in the caller's address space.
  76 .TP
  77 .B EINVAL
  78 Invalid
  79 .I length
  80 argument.
  81 .TP
  82 .B ENODEV
  83 PCI support is not enabled.
  84 .TP
  85 .B ENOMEM
  86 Insufficient memory.
  87 .SH VERSIONS
  88 These system calls are available since Linux 3.19.
  89 .SH CONFORMING TO
  90 This Linux-specific system call is available only on the s390 architecture.
  91 The required PCI support is available beginning with System z EC12.
  92 .SH SEE ALSO
  93 .BR syscall (2)