adfs: add hexadecimal filetype suffix option

ADFS (FileCore) storage complies with the RISC OS filetype specification
(12 bits of file type information is stored in the file load address,
rather than using a file extension).  The existing driver largely ignores
this information and does not present it to the end user.

It is desirable that stored filetypes be made visible to the end user to
facilitate a precise copy of data and metadata from a hard disc (or image
thereof) into a RISC OS emulator (such as RPCEmu) or to a network share
which can be accessed by real Acorn systems.

This patch implements a per-mount filetype suffix option (use -o
ftsuffix=1) to present any filetype as a ,xyz hexadecimal suffix on each
file.  This type suffix is compatible with that used by RISC OS systems
that access network servers using NFS client software and by RPCemu's host
filing system.

Signed-off-by: Stuart Swales <stuart.swales.croftnuisk@gmail.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/Documentation/filesystems/adfs.txt b/Documentation/filesystems/adfs.txt
index 9e8811f92b84..5949766353f7 100644
--- a/Documentation/filesystems/adfs.txt
+++ b/Documentation/filesystems/adfs.txt
@@ -9,6 +9,9 @@ Mount options for ADFS
 		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
 ------------------------------------------------
@@ -55,3 +58,18 @@ Mapping of ADFS permissions to Linux permissions
 
   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.