1 /* 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 */ 22 static 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, maxpages, lpages; 31 32 if (!mtd) 33 goto cant_map_directly; 34 35 /* the mapping mustn't extend beyond the EOF */ 36 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 37 isize = i_size_read(inode); 38 offset = pgoff << PAGE_SHIFT; 39 40 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 41 if ((pgoff >= maxpages) || (maxpages - pgoff < lpages)) 42 return (unsigned long) -EINVAL; 43 44 /* we need to call down to the MTD layer to do the actual mapping */ 45 if (mtd->get_unmapped_area) { 46 if (addr != 0) 47 return (unsigned long) -EINVAL; 48 49 if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT)) 50 return (unsigned long) -EINVAL; 51 52 offset += ROMFS_I(inode)->i_dataoffset; 53 if (offset > mtd->size - len) 54 return (unsigned long) -EINVAL; 55 56 return mtd->get_unmapped_area(mtd, len, offset, flags); 57 } 58 59 cant_map_directly: 60 return (unsigned long) -ENOSYS; 61 } 62 63 /* 64 * permit a R/O mapping to be made directly through onto an MTD device if 65 * possible 66 */ 67 static int romfs_mmap(struct file *file, struct vm_area_struct *vma) 68 { 69 return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS; 70 } 71 72 const struct file_operations romfs_ro_fops = { 73 .llseek = generic_file_llseek, 74 .read = do_sync_read, 75 .aio_read = generic_file_aio_read, 76 .splice_read = generic_file_splice_read, 77 .mmap = romfs_mmap, 78 .get_unmapped_area = romfs_get_unmapped_area, 79 }; 80