arch/arc/kernel/arc_hostlink.c

   1 /*
   2  * arc_hostlink.c: Pseudo-driver for Metaware provided "hostlink" facility
   3  *
   4  * Allows Linux userland access to host in absence of any peripherals.
   5  *
   6  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/fs.h>           /* file_operations */
  14 #include <linux/miscdevice.h>
  15 #include <linux/mm.h>           /* VM_IO */
  16 #include <linux/module.h>
  17 #include <linux/uaccess.h>
  18
  19 static unsigned char __HOSTLINK__[4 * PAGE_SIZE] __aligned(PAGE_SIZE);
  20
  21 static int arc_hl_mmap(struct file *fp, struct vm_area_struct *vma)
  22 {
  23         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
  24
  25         if (io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
  26                                vma->vm_end - vma->vm_start,
  27                                vma->vm_page_prot)) {
  28                 pr_warn("Hostlink buffer mmap ERROR\n");
  29                 return -EAGAIN;
  30         }
  31         return 0;
  32 }
  33
  34 static long arc_hl_ioctl(struct file *file, unsigned int cmd,
  35                         unsigned long arg)
  36 {
  37         /* we only support, returning the physical addr to mmap in user space */
  38         put_user((unsigned int)__HOSTLINK__, (int __user *)arg);
  39         return 0;
  40 }
  41
  42 static const struct file_operations arc_hl_fops = {
  43         .unlocked_ioctl = arc_hl_ioctl,
  44         .mmap           = arc_hl_mmap,
  45 };
  46
  47 static struct miscdevice arc_hl_dev = {
  48         .minor  = MISC_DYNAMIC_MINOR,
  49         .name   = "hostlink",
  50         .fops   = &arc_hl_fops
  51 };
  52
  53 static int __init arc_hl_init(void)
  54 {
  55         pr_info("ARC Hostlink driver mmap at 0x%p\n", __HOSTLINK__);
  56         return misc_register(&arc_hl_dev);
  57 }
  58 module_init(arc_hl_init);