linux/arch/arc/kernel/arc_hostlink.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * arc_hostlink.c: Pseudo-driver for Metaware provided "hostlink" facility
   4 *
   5 * Allows Linux userland access to host in absence of any peripherals.
   6 *
   7 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   8 */
   9
  10#include <linux/fs.h>           /* file_operations */
  11#include <linux/miscdevice.h>
  12#include <linux/mm.h>           /* VM_IO */
  13#include <linux/module.h>
  14#include <linux/uaccess.h>
  15
  16static unsigned char __HOSTLINK__[4 * PAGE_SIZE] __aligned(PAGE_SIZE);
  17
  18static int arc_hl_mmap(struct file *fp, struct vm_area_struct *vma)
  19{
  20        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
  21
  22        if (io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
  23                               vma->vm_end - vma->vm_start,
  24                               vma->vm_page_prot)) {
  25                pr_warn("Hostlink buffer mmap ERROR\n");
  26                return -EAGAIN;
  27        }
  28        return 0;
  29}
  30
  31static long arc_hl_ioctl(struct file *file, unsigned int cmd,
  32                        unsigned long arg)
  33{
  34        /* we only support, returning the physical addr to mmap in user space */
  35        put_user((unsigned int)__HOSTLINK__, (int __user *)arg);
  36        return 0;
  37}
  38
  39static const struct file_operations arc_hl_fops = {
  40        .unlocked_ioctl = arc_hl_ioctl,
  41        .mmap           = arc_hl_mmap,
  42};
  43
  44static struct miscdevice arc_hl_dev = {
  45        .minor  = MISC_DYNAMIC_MINOR,
  46        .name   = "hostlink",
  47        .fops   = &arc_hl_fops
  48};
  49
  50static int __init arc_hl_init(void)
  51{
  52        pr_info("ARC Hostlink driver mmap at 0x%p\n", __HOSTLINK__);
  53        return misc_register(&arc_hl_dev);
  54}
  55module_init(arc_hl_init);
  56
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