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man page for s390_pci_mmio_write

S390_PCI_MMIO_WRITE(2)						System Calls Manual					    S390_PCI_MMIO_WRITE(2)

s390_pci_mmio_write, s390_pci_mmio_read - transfer data to/from PCI MMIO memory page SYNOPSIS
#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); 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 map- ping 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 error, -1 is returned and errno is set to one of the error codes listed below. 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. CONFORMING TO
This Linux-specific system call is available only on the s390 architecture. The required PCI support is available beginning with System z EC12. NOTES
Glibc does not provide a wrapper for this system call, use syscall(2) to call it. SEE ALSO
syscall(2) Linux Programmer's Manual 2017-09-15 S390_PCI_MMIO_WRITE(2)

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