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author | Mauro Carvalho Chehab <mchehab+huawei@kernel.org> | 2020-02-17 17:11:48 +0100 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2020-03-02 13:58:44 -0700 |
commit | 348739003d4f7e777ef935a44a91e7494f8ab786 (patch) | |
tree | a92329123dbb7a9cfaaab3ee7ce12c755e09d2b5 /Documentation/filesystems/adfs.rst | |
parent | 07d241fd66ba99111d43a0a4c4abeeb972468d1d (diff) | |
download | linux-348739003d4f7e777ef935a44a91e7494f8ab786.tar.bz2 |
docs: filesystems: convert adfs.txt to ReST
- Add a SPDX header;
- Add a document title;
- Adjust section titles;
- Mark literal blocks as such;
- Add it to filesystems/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/15ee92f03ec917e5d26bd7b863565dec88c843f6.1581955849.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/filesystems/adfs.rst')
-rw-r--r-- | Documentation/filesystems/adfs.rst | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/Documentation/filesystems/adfs.rst b/Documentation/filesystems/adfs.rst new file mode 100644 index 000000000000..5b22cae38e5e --- /dev/null +++ b/Documentation/filesystems/adfs.rst @@ -0,0 +1,108 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============================== +Acorn Disc Filing System - ADFS +=============================== + +Filesystems supported by ADFS +----------------------------- + +The ADFS module supports the following Filecore formats which have: + +- new maps +- new directories or big directories + +In terms of the named formats, this means we support: + +- E and E+, with or without boot block +- F and F+ + +We fully support reading files from these filesystems, and writing to +existing files within their existing allocation. Essentially, we do +not support changing any of the filesystem metadata. + +This is intended to support loopback mounted Linux native filesystems +on a RISC OS Filecore filesystem, but will allow the data within files +to be changed. + +If write support (ADFS_FS_RW) is configured, we allow rudimentary +directory updates, specifically updating the access mode and timestamp. + +Mount options for ADFS +---------------------- + + ============ ====================================================== + uid=nnn All files in the partition will be owned by + user id nnn. Default 0 (root). + gid=nnn All files in the partition will be in group + nnn. Default 0 (root). + ownmask=nnn The permission mask for ADFS 'owner' permissions + will be nnn. Default 0700. + othmask=nnn The permission mask for ADFS 'other' permissions + will be nnn. Default 0077. + ftsuffix=n When ftsuffix=0, no file type suffix will be applied. + When ftsuffix=1, a hexadecimal suffix corresponding to + the RISC OS file type will be added. Default 0. + ============ ====================================================== + +Mapping of ADFS permissions to Linux permissions +------------------------------------------------ + + ADFS permissions consist of the following: + + - Owner read + - Owner write + - Other read + - Other write + + (In older versions, an 'execute' permission did exist, but this + does not hold the same meaning as the Linux 'execute' permission + and is now obsolete). + + The mapping is performed as follows:: + + Owner read -> -r--r--r-- + Owner write -> --w--w---w + Owner read and filetype UnixExec -> ---x--x--x + These are then masked by ownmask, eg 700 -> -rwx------ + Possible owner mode permissions -> -rwx------ + + Other read -> -r--r--r-- + Other write -> --w--w--w- + Other read and filetype UnixExec -> ---x--x--x + These are then masked by othmask, eg 077 -> ----rwxrwx + Possible other mode permissions -> ----rwxrwx + + Hence, with the default masks, if a file is owner read/write, and + not a UnixExec filetype, then the permissions will be:: + + -rw------- + + However, if the masks were ownmask=0770,othmask=0007, then this would + be modified to:: + + -rw-rw---- + + There is no restriction on what you can do with these masks. You may + wish that either read bits give read access to the file for all, but + keep the default write protection (ownmask=0755,othmask=0577):: + + -rw-r--r-- + + You can therefore tailor the permission translation to whatever you + desire the permissions should be under Linux. + +RISC OS file type suffix +------------------------ + + RISC OS file types are stored in bits 19..8 of the file load address. + + To enable non-RISC OS systems to be used to store files without losing + file type information, a file naming convention was devised (initially + for use with NFS) such that a hexadecimal suffix of the form ,xyz + denoted the file type: e.g. BasicFile,ffb is a BASIC (0xffb) file. This + naming convention is now also used by RISC OS emulators such as RPCEmu. + + Mounting an ADFS disc with option ftsuffix=1 will cause appropriate file + type suffixes to be appended to file names read from a directory. If the + ftsuffix option is zero or omitted, no file type suffixes will be added. |