NOMMU: Make it possible for RomFS to use MTD devices directly

[linux-2.6-microblaze.git] / fs / romfs / mmap-nommu.c

diff --git a/fs/romfs/mmap-nommu.c b/fs/romfs/mmap-nommu.c
new file mode 100644 (file)
index 0000000..f0511e8
--- /dev/null
+++ b/fs/romfs/mmap-nommu.c
@@ -0,0 +1,75 @@
+/* NOMMU mmap support for RomFS on MTD devices
+ *
+ * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/mm.h>
+#include <linux/mtd/super.h>
+#include "internal.h"
+
+/*
+ * try to determine where a shared mapping can be made
+ * - only supported for NOMMU at the moment (MMU can't doesn't copy private
+ *   mappings)
+ * - attempts to map through to the underlying MTD device
+ */
+static unsigned long romfs_get_unmapped_area(struct file *file,
+                                            unsigned long addr,
+                                            unsigned long len,
+                                            unsigned long pgoff,
+                                            unsigned long flags)
+{
+       struct inode *inode = file->f_mapping->host;
+       struct mtd_info *mtd = inode->i_sb->s_mtd;
+       unsigned long isize, offset;
+
+       if (!mtd)
+               goto cant_map_directly;
+
+       isize = i_size_read(inode);
+       offset = pgoff << PAGE_SHIFT;
+       if (offset > isize || len > isize || offset > isize - len)
+               return (unsigned long) -EINVAL;
+
+       /* we need to call down to the MTD layer to do the actual mapping */
+       if (mtd->get_unmapped_area) {
+               if (addr != 0)
+                       return (unsigned long) -EINVAL;
+
+               if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
+                       return (unsigned long) -EINVAL;
+
+               offset += ROMFS_I(inode)->i_dataoffset;
+               if (offset > mtd->size - len)
+                       return (unsigned long) -EINVAL;
+
+               return mtd->get_unmapped_area(mtd, len, offset, flags);
+       }
+
+cant_map_directly:
+       return (unsigned long) -ENOSYS;
+}
+
+/*
+ * permit a R/O mapping to be made directly through onto an MTD device if
+ * possible
+ */
+static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+       return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
+}
+
+const struct file_operations romfs_ro_fops = {
+       .llseek                 = generic_file_llseek,
+       .read                   = do_sync_read,
+       .aio_read               = generic_file_aio_read,
+       .splice_read            = generic_file_splice_read,
+       .mmap                   = romfs_mmap,
+       .get_unmapped_area      = romfs_get_unmapped_area,
+};