Without further ado, the following was found: Issue: to the user-space buffer I<user_buffer> → and writes them to the user-space buffer I<user_buffer> "The B<s390_pci_mmio_write>() system call writes I<length> bytes of data " "from the user-space buffer I<user_buffer> to the PCI MMIO memory location " "specified by I<mmio_addr>. The B<s390_pci_mmio_read>() system call reads " "I<length> bytes of data from the PCI MMIO memory location specified by " "I<mmio_addr> to the user-space buffer I<user_buffer>."