Case:		2005/360    Document and enable visibility of hidden files in pcfs

Author:		Frank Hofmann

Summary:
	This proposal requests, for Patch binding,
	* to elevate the interface status of the existing pcfs mount
	  options "hidden"/"nohidden" from "Private" to "Unstable"
	  commitment level. I.e. document this feature.
	* to change the default behaviour of pcfs so that "-o hidden"
	  (the ability to see files on a FAT filesystem that have the
	   'hidden' FAT attribute bit set) becomes the default.

The Problem
	The original submission for PSARC 1996/443 contained the pcfs-
	specific mount options "-o hidden" and "-o nohidden" which
	enabled users of the pcfs filesystem to see files that have
	the (non-UNIX, non-POSIX) 'hidden' FAT file attribute set.
	While the code that was delivered for 1996/443 had support for
	these options in, they had been withdrawn from the approved part
	of PSARC 1996/443. The reasons for why "hidden" was withdrawn were:
	1. No agreement could be reached regarding the name of the
	   mount option to "make hidden files visible".
	2. No agreement could be reached regarding the (impossible)
	   mapping of FAT attributes to the 'generic' POSIX file
	   permission bits, and the (un)necessity for Solaris utilities
	   to switch on/off pcfs-specific file attributes.
	   Lacking this, support for accessing hidden files on pcfs
	   was considered "a hack".
	3. No market was seen for allowing access to hidden files.
	   Quote from the mail archive for PSARC 1996/443:
		Most users can't see hidden files under DOS or Windows
		anyway; they have to get special tools to change them,
		tools that are the equivalent of fsdb.
	   This was incorrect even in 1996, so the decision not to
	   productize "hidden"/"nohidden" was based on incorrect facts.

	This situation has significantly changed eight years later.
	- It is trivial today (a switch accessible in Windows' Explorer
	  Menus) to see hidden files on a FAT filesystem under Microsoft
	  Windows. That's far from requiring "the equivalent of fsdb".
	- A mapping between filesystem-specific attributes and POSIX
	  attributes (in full consequence: An extension of the POSIX
	  file attribute set) has not been done. Extended file attributes
	  are still not a POSIX standard, and the generic development in
	  other filesystems on Solaris has made such "fs-specific attributes"
	  into mount options or ioctls (example: ufs' handling of direct I/O).
	  The advice given in PSARC 1996/443 therefore can be considered
	  obsolete.
	- there's a market: Some Digital Camera and portable music player
	  manufacturers (noticeably Apple's Ipod device) are using FAT
	  filesystems and turn on the 'hidden' bit for ALL files on that
	  device's mass storage. Which means support for reading/writing
	  the data on such devices depends on making their contents
	  visible. See RFE 1181439.

The Proposed Solution

	PCFS will turn on the "hidden" mount option by default, making
	hidden files visible to the user. This gives the most consistent
	user experience by not hiding information from the user by default.
	Disabling the feature is still an option available to the system
	administrator if so desired. To do that, the system will revert to
	the current behaviour if the "nohidden" mount option is explicitly
	used.

	Reasoning
	=========

	Other alternatives such as having PCFS rename files with the
	"hidden" PCFS attribute set to the UNIX-style ".hiddenfile"
	(i.e prepend a filename with '.' to make it invisible in a
	'ls' without '-l' option) were discussed but this causes
	ambiguities as well as failure of existing applications that
	expect to see files with a given name, a "hidden" attribute
	notwithstanding. A real-world example application that
	behaves like this is the UNIX program "gtkpod" that allows
	access to Apple iPod music players.

	Likewise, just documenting the existance of "hidden"/"nohidden"
	mount options but not changing the default behaviour causes
	bad user experience, because access to such files will need
	explicit operator intervention, which again makes existing
	applications fail which just expect to see such files.
	The example for this is again "gtkpod".

	Retaining and documenting the current "hidden"/"nohidden"
	mount options but making "hidden" (show hidden files)
	the default behaviour has the advantages:
	1. No surprise to users/admins who found out about the
	   undocumented options via Usenet, Solaris headers or
	   www.opensolaris.org sourcecode.
	2. No surprise to applications written for Linux, *BSD
	   or MacOSX, which do not perform any "name translation"
	   for hidden files. Such applications just work.
	3. By far the best cost/benefit ratio of all options.

	Note on "system" files
	======================
	The (also non-POSIX) "system" PCFS file attribute has no
	bearing in this case - "system" does not imply "hidden".
	This case does not attempt to define/modify PCFS's
	behaviour wrt. to files having the "system" attribute
	being set/unset.

MAN PAGE CHANGES

	The man page for mount_pcfs(1M) will be changed to include
	usage instructions on the "hidden"/"nohidden" mount options.
	It will also be changed to state that "hidden" is the new
	default behaviour.

	The man page for pcfs(7FS) describes the current behaviour
	(hidden files not being shown) under "BUGS". That section
	will be removed.

	An example on how to use the "nohidden" mount option will
	be added to the Examples section of rmmount.conf(4).

	Manpage diffs are available.