blob: f0511e8169679fa3872938a2a9e0e9c19998049b [file] [log] [blame]
David Howellsda4458b2009-02-12 10:40:10 +00001/* NOMMU mmap support for RomFS on MTD devices
2 *
3 * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/mm.h>
13#include <linux/mtd/super.h>
14#include "internal.h"
15
16/*
17 * try to determine where a shared mapping can be made
18 * - only supported for NOMMU at the moment (MMU can't doesn't copy private
19 * mappings)
20 * - attempts to map through to the underlying MTD device
21 */
22static unsigned long romfs_get_unmapped_area(struct file *file,
23 unsigned long addr,
24 unsigned long len,
25 unsigned long pgoff,
26 unsigned long flags)
27{
28 struct inode *inode = file->f_mapping->host;
29 struct mtd_info *mtd = inode->i_sb->s_mtd;
30 unsigned long isize, offset;
31
32 if (!mtd)
33 goto cant_map_directly;
34
35 isize = i_size_read(inode);
36 offset = pgoff << PAGE_SHIFT;
37 if (offset > isize || len > isize || offset > isize - len)
38 return (unsigned long) -EINVAL;
39
40 /* we need to call down to the MTD layer to do the actual mapping */
41 if (mtd->get_unmapped_area) {
42 if (addr != 0)
43 return (unsigned long) -EINVAL;
44
45 if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
46 return (unsigned long) -EINVAL;
47
48 offset += ROMFS_I(inode)->i_dataoffset;
49 if (offset > mtd->size - len)
50 return (unsigned long) -EINVAL;
51
52 return mtd->get_unmapped_area(mtd, len, offset, flags);
53 }
54
55cant_map_directly:
56 return (unsigned long) -ENOSYS;
57}
58
59/*
60 * permit a R/O mapping to be made directly through onto an MTD device if
61 * possible
62 */
63static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
64{
65 return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
66}
67
68const struct file_operations romfs_ro_fops = {
69 .llseek = generic_file_llseek,
70 .read = do_sync_read,
71 .aio_read = generic_file_aio_read,
72 .splice_read = generic_file_splice_read,
73 .mmap = romfs_mmap,
74 .get_unmapped_area = romfs_get_unmapped_area,
75};