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 
16 static unsigned char __HOSTLINK__[4 * PAGE_SIZE] __aligned(PAGE_SIZE);
17 
arc_hl_mmap(struct file * fp,struct vm_area_struct * vma)18 static 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 
arc_hl_ioctl(struct file * file,unsigned int cmd,unsigned long arg)31 static 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 
39 static const struct file_operations arc_hl_fops = {
40 	.unlocked_ioctl	= arc_hl_ioctl,
41 	.mmap		= arc_hl_mmap,
42 };
43 
44 static struct miscdevice arc_hl_dev = {
45 	.minor	= MISC_DYNAMIC_MINOR,
46 	.name	= "hostlink",
47 	.fops	= &arc_hl_fops
48 };
49 
arc_hl_init(void)50 static 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 }
55 module_init(arc_hl_init);
56