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; 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 55 cant_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 */ 63 static 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 68 const 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 }; 76