base.c

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

/*  devfs (Device FileSystem) driver.

    Copyright (C) 1998-2002  Richard Gooch

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    Richard Gooch may be reached by email at  [e-mail]
    The postal address is:
      Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.

    ChangeLog

    19980110   Richard Gooch <[e-mail]>
               Original version.
  v0.1
    19980111   Richard Gooch <[e-mail]>
               Created per-fs inode table rather than using inode->u.generic_ip
  v0.2
    19980111   Richard Gooch <[e-mail]>
               Created .epoch inode which has a ctime of 0.
	       Fixed loss of named pipes when dentries lost.
	       Fixed loss of inode data when devfs_register() follows mknod().
  v0.3
    19980111   Richard Gooch <[e-mail]>
               Fix for when compiling with CONFIG_KERNELD.
    19980112   Richard Gooch <[e-mail]>
               Fix for readdir() which sometimes didn't show entries.
	       Added <<tolerant>> option to <devfs_register>.
  v0.4
    19980113   Richard Gooch <[e-mail]>
               Created <devfs_fill_file> function.
  v0.5
    19980115   Richard Gooch <[e-mail]>
               Added subdirectory support. Major restructuring.
    19980116   Richard Gooch <[e-mail]>
               Fixed <find_by_dev> to not search major=0,minor=0.
	       Added symlink support.
  v0.6
    19980120   Richard Gooch <[e-mail]>
               Created <devfs_mk_dir> function and support directory unregister
    19980120   Richard Gooch <[e-mail]>
               Auto-ownership uses real uid/gid rather than effective uid/gid.
  v0.7
    19980121   Richard Gooch <[e-mail]>
               Supported creation of sockets.
  v0.8
    19980122   Richard Gooch <[e-mail]>
               Added DEVFS_FL_HIDE_UNREG flag.
	       Interface change to <devfs_mk_symlink>.
               Created <devfs_symlink> to support symlink(2).
  v0.9
    19980123   Richard Gooch <[e-mail]>
               Added check to <devfs_fill_file> to check inode is in devfs.
	       Added optional traversal of symlinks.
  v0.10
    19980124   Richard Gooch <[e-mail]>
               Created <devfs_get_flags> and <devfs_set_flags>.
  v0.11
    19980125   C. Scott Ananian <[e-mail]>
               Created <devfs_find_handle>.
    19980125   Richard Gooch <[e-mail]>
               Allow removal of symlinks.
  v0.12
    19980125   Richard Gooch <[e-mail]>
               Created <devfs_set_symlink_destination>.
    19980126   Richard Gooch <[e-mail]>
               Moved DEVFS_SUPER_MAGIC into header file.
	       Added DEVFS_FL_HIDE flag.
	       Created <devfs_get_maj_min>.
	       Created <devfs_get_handle_from_inode>.
	       Fixed minor bug in <find_by_dev>.
    19980127   Richard Gooch <[e-mail]>
	       Changed interface to <find_by_dev>, <find_entry>,
	       <devfs_unregister>, <devfs_fill_file> and <devfs_find_handle>.
	       Fixed inode times when symlink created with symlink(2).
  v0.13
    19980129   C. Scott Ananian <[e-mail]>
               Exported <devfs_set_symlink_destination>, <devfs_get_maj_min>
	       and <devfs_get_handle_from_inode>.
    19980129   Richard Gooch <[e-mail]>
	       Created <devfs_unlink> to support unlink(2).
  v0.14
    19980129   Richard Gooch <[e-mail]>
	       Fixed kerneld support for entries in devfs subdirectories.
    19980130   Richard Gooch <[e-mail]>
	       Bugfixes in <call_kerneld>.
  v0.15
    19980207   Richard Gooch <[e-mail]>
	       Call kerneld when looking up unregistered entries.
  v0.16
    19980326   Richard Gooch <[e-mail]>
	       Modified interface to <devfs_find_handle> for symlink traversal.
  v0.17
    19980331   Richard Gooch <[e-mail]>
	       Fixed persistence bug with device numbers for manually created
	       device files.
	       Fixed problem with recreating symlinks with different content.
  v0.18
    19980401   Richard Gooch <[e-mail]>
	       Changed to CONFIG_KMOD.
	       Hide entries which are manually unlinked.
	       Always invalidate devfs dentry cache when registering entries.
	       Created <devfs_rmdir> to support rmdir(2).
	       Ensure directories created by <devfs_mk_dir> are visible.
  v0.19
    19980402   Richard Gooch <[e-mail]>
	       Invalidate devfs dentry cache when making directories.
	       Invalidate devfs dentry cache when removing entries.
	       Fixed persistence bug with fifos.
  v0.20
    19980421   Richard Gooch <[e-mail]>
	       Print process command when debugging kerneld/kmod.
	       Added debugging for register/unregister/change operations.
    19980422   Richard Gooch <[e-mail]>
	       Added "devfs=" boot options.
  v0.21
    19980426   Richard Gooch <[e-mail]>
	       No longer lock/unlock superblock in <devfs_put_super>.
	       Drop negative dentries when they are released.
	       Manage dcache more efficiently.
  v0.22
    19980427   Richard Gooch <[e-mail]>
	       Added DEVFS_FL_AUTO_DEVNUM flag.
  v0.23
    19980430   Richard Gooch <[e-mail]>
	       No longer set unnecessary methods.
  v0.24
    19980504   Richard Gooch <[e-mail]>
	       Added PID display to <call_kerneld> debugging message.
	       Added "after" debugging message to <call_kerneld>.
    19980519   Richard Gooch <[e-mail]>
	       Added "diread" and "diwrite" boot options.
    19980520   Richard Gooch <[e-mail]>
	       Fixed persistence problem with permissions.
  v0.25
    19980602   Richard Gooch <[e-mail]>
	       Support legacy device nodes.
	       Fixed bug where recreated inodes were hidden.
  v0.26
    19980602   Richard Gooch <[e-mail]>
	       Improved debugging in <get_vfs_inode>.
    19980607   Richard Gooch <[e-mail]>
	       No longer free old dentries in <devfs_mk_dir>.
	       Free all dentries for a given entry when deleting inodes.
  v0.27
    19980627   Richard Gooch <[e-mail]>
	       Limit auto-device numbering to majors 128 to 239.
  v0.28
    19980629   Richard Gooch <[e-mail]>
	       Fixed inode times persistence problem.
  v0.29
    19980704   Richard Gooch <[e-mail]>
	       Fixed spelling in <devfs_readlink> debug.
	       Fixed bug in <devfs_setup> parsing "dilookup".
  v0.30
    19980705   Richard Gooch <[e-mail]>
	       Fixed devfs inode leak when manually recreating inodes.
	       Fixed permission persistence problem when recreating inodes.
  v0.31
    19980727   Richard Gooch <[e-mail]>
	       Removed harmless "unused variable" compiler warning.
	       Fixed modes for manually recreated device nodes.
  v0.32
    19980728   Richard Gooch <[e-mail]>
	       Added NULL devfs inode warning in <devfs_read_inode>.
	       Force all inode nlink values to 1.
  v0.33
    19980730   Richard Gooch <[e-mail]>
	       Added "dimknod" boot option.
	       Set inode nlink to 0 when freeing dentries.
	       Fixed modes for manually recreated symlinks.
  v0.34
    19980802   Richard Gooch <[e-mail]>
	       Fixed bugs in recreated directories and symlinks.
  v0.35
    19980806   Richard Gooch <[e-mail]>
	       Fixed bugs in recreated device nodes.
    19980807   Richard Gooch <[e-mail]>
	       Fixed bug in currently unused <devfs_get_handle_from_inode>.
	       Defined new <devfs_handle_t> type.
	       Improved debugging when getting entries.
	       Fixed bug where directories could be emptied.
  v0.36
    19980809   Richard Gooch <[e-mail]>
	       Replaced dummy .epoch inode with .devfsd character device.
    19980810   Richard Gooch <[e-mail]>
	       Implemented devfsd protocol revision 0.
  v0.37
    19980819   Richard Gooch <[e-mail]>
	       Added soothing message to warning in <devfs_d_iput>.
  v0.38
    19980829   Richard Gooch <[e-mail]>
	       Use GCC extensions for structure initialisations.
	       Implemented async open notification.
	       Incremented devfsd protocol revision to 1.
  v0.39
    19980908   Richard Gooch <[e-mail]>
	       Moved async open notification to end of <devfs_open>.
  v0.40
    19980910   Richard Gooch <[e-mail]>
	       Prepended "/dev/" to module load request.
	       Renamed <call_kerneld> to <call_kmod>.
  v0.41
    19980910   Richard Gooch <[e-mail]>
	       Fixed typo "AYSNC" -> "ASYNC".
  v0.42
    19980910   Richard Gooch <[e-mail]>
	       Added open flag for files.
  v0.43
    19980927   Richard Gooch <[e-mail]>
	       Set i_blocks=0 and i_blksize=1024 in <devfs_read_inode>.
  v0.44
    19981005   Richard Gooch <[e-mail]>
	       Added test for empty <<name>> in <devfs_find_handle>.
	       Renamed <generate_path> to <devfs_generate_path> and published.
  v0.45
    19981006   Richard Gooch <[e-mail]>
	       Created <devfs_get_fops>.
  v0.46
    19981007   Richard Gooch <[e-mail]>
	       Limit auto-device numbering to majors 144 to 239.
  v0.47
    19981010   Richard Gooch <[e-mail]>
	       Updated <devfs_follow_link> for VFS change in 2.1.125.
  v0.48
    19981022   Richard Gooch <[e-mail]>
	       Created DEVFS_ FL_COMPAT flag.
  v0.49
    19981023   Richard Gooch <[e-mail]>
	       Created "nocompat" boot option.
  v0.50
    19981025   Richard Gooch <[e-mail]>
	       Replaced "mount" boot option with "nomount".
  v0.51
    19981110   Richard Gooch <[e-mail]>
	       Created "only" boot option.
  v0.52
    19981112   Richard Gooch <[e-mail]>
	       Added DEVFS_FL_REMOVABLE flag.
  v0.53
    19981114   Richard Gooch <[e-mail]>
	       Only call <scan_dir_for_removable> on first call to
	       <devfs_readdir>.
  v0.54
    19981205   Richard Gooch <[e-mail]>
	       Updated <devfs_rmdir> for VFS change in 2.1.131.
  v0.55
    19981218   Richard Gooch <[e-mail]>
	       Created <devfs_mk_compat>.
    19981220   Richard Gooch <[e-mail]>
	       Check for partitions on removable media in <devfs_lookup>.
  v0.56
    19990118   Richard Gooch <[e-mail]>
	       Added support for registering regular files.
	       Created <devfs_set_file_size>.
	       Update devfs inodes from entries if not changed through FS.
  v0.57
    19990124   Richard Gooch <[e-mail]>
	       Fixed <devfs_fill_file> to only initialise temporary inodes.
	       Trap for NULL fops in <devfs_register>.
	       Return -ENODEV in <devfs_fill_file> for non-driver inodes.
  v0.58
    19990126   Richard Gooch <[e-mail]>
	       Switched from PATH_MAX to DEVFS_PATHLEN.
  v0.59
    19990127   Richard Gooch <[e-mail]>
	       Created "nottycompat" boot option.
  v0.60
    19990318   Richard Gooch <[e-mail]>
	       Fixed <devfsd_read> to not overrun event buffer.
  v0.61
    19990329   Richard Gooch <[e-mail]>
	       Created <devfs_auto_unregister>.
  v0.62
    19990330   Richard Gooch <[e-mail]>
	       Don't return unregistred entries in <devfs_find_handle>.
	       Panic in <devfs_unregister> if entry unregistered.
    19990401   Richard Gooch <[e-mail]>
	       Don't panic in <devfs_auto_unregister> for duplicates.
  v0.63
    19990402   Richard Gooch <[e-mail]>
	       Don't unregister already unregistered entries in <unregister>.
  v0.64
    19990510   Richard Gooch <[e-mail]>
	       Disable warning messages when unable to read partition table for
	       removable media.
  v0.65
    19990512   Richard Gooch <[e-mail]>
	       Updated <devfs_lookup> for VFS change in 2.3.1-pre1.
	       Created "oops-on-panic" boot option.
	       Improved debugging in <devfs_register> and <devfs_unregister>.
  v0.66
    19990519   Richard Gooch <[e-mail]>
	       Added documentation for some functions.
    19990525   Richard Gooch <[e-mail]>
	       Removed "oops-on-panic" boot option: now always Oops.
  v0.67
    19990531   Richard Gooch <[e-mail]>
	       Improved debugging in <devfs_register>.
  v0.68
    19990604   Richard Gooch <[e-mail]>
	       Added "diunlink" and "nokmod" boot options.
	       Removed superfluous warning message in <devfs_d_iput>.
  v0.69
    19990611   Richard Gooch <[e-mail]>
	       Took account of change to <d_alloc_root>.
  v0.70
    19990614   Richard Gooch <[e-mail]>
	       Created separate event queue for each mounted devfs.
	       Removed <devfs_invalidate_dcache>.
	       Created new ioctl()s.
	       Incremented devfsd protocol revision to 3.
	       Fixed bug when re-creating directories: contents were lost.
	       Block access to inodes until devfsd updates permissions.
    19990615   Richard Gooch <[e-mail]>
	       Support 2.2.x kernels.
  v0.71
    19990623   Richard Gooch <[e-mail]>
	       Switched to sending process uid/gid to devfsd.
	       Renamed <call_kmod> to <try_modload>.
	       Added DEVFSD_NOTIFY_LOOKUP event.
    19990624   Richard Gooch <[e-mail]>
	       Added DEVFSD_NOTIFY_CHANGE event.
	       Incremented devfsd protocol revision to 4.
  v0.72
    19990713   Richard Gooch <[e-mail]>
	       Return EISDIR rather than EINVAL for read(2) on directories.
  v0.73
    19990809   Richard Gooch <[e-mail]>
	       Changed <devfs_setup> to new __init scheme.
  v0.74
    19990901   Richard Gooch <[e-mail]>
	       Changed remaining function declarations to new __init scheme.
  v0.75
    19991013   Richard Gooch <[e-mail]>
	       Created <devfs_get_info>, <devfs_set_info>,
	       <devfs_get_first_child> and <devfs_get_next_sibling>.
	       Added <<dir>> parameter to <devfs_register>, <devfs_mk_compat>,
	       <devfs_mk_dir> and <devfs_find_handle>.
	       Work sponsored by SGI.
  v0.76
    19991017   Richard Gooch <[e-mail]>
	       Allow multiple unregistrations.
	       Work sponsored by SGI.
  v0.77
    19991026   Richard Gooch <[e-mail]>
	       Added major and minor number to devfsd protocol.
	       Incremented devfsd protocol revision to 5.
	       Work sponsored by SGI.
  v0.78
    19991030   Richard Gooch <[e-mail]>
	       Support info pointer for all devfs entry types.
	       Added <<info>> parameter to <devfs_mk_dir> and
	       <devfs_mk_symlink>.
	       Work sponsored by SGI.
  v0.79
    19991031   Richard Gooch <[e-mail]>
	       Support "../" when searching devfs namespace.
	       Work sponsored by SGI.
  v0.80
    19991101   Richard Gooch <[e-mail]>
	       Created <devfs_get_unregister_slave>.
	       Work sponsored by SGI.
  v0.81
    19991103   Richard Gooch <[e-mail]>
	       Exported <devfs_get_parent>.
	       Work sponsored by SGI.