> Date: Tue, 12 Jul 1994 15:35:31 -0400
> From: "Chris G. Demetriou" <cgd@alpha.bostic.com>

> Actually, it's a bit unclear what the appropriate behaviour is...

Agreed.  P1003.1 describes the error codes, but a much more useful
presentation of "what error code should I use for this" is given in
the recommendation 1003.1 N327 by Paul Rabin (3/16/93).

Relevant parts: (sorry, I only have it on paper)

    ENOTSUP "Not supported"

    Use [it] to indicate that the requested operation, though
    supported in general, is not supported by teh implementation
    for the requested object or the requested argument. 

    ENOSYS "Function not implemented"

    Use [it] to indicate that the requested operation is not supported
    by the implementation for any object or argument.

    ENOTTY "Inappropriate I/O control operation"

    Use [it] to indicate that an attempt was made to apply an
    operation that is meaningful only on tty devices to an object that
    is not a tty device.

    ENXIO "No such device or address"

    Use [it] to indicate taht a referenced hardware device does not
    exist or is unavailable, or that the request is out of range for
    the device.

Based on these recommendations, I would suggest that the vnode "disk"
driver should return ENOTSUP for the DIOC* ioctls, because the ioctls
indeed are sometimes supported, just not for this object.

Gordon W. Ross			  Internet: <gwr@mc.com>
Mercury Computer Systems	Voice mail: 508-256-0052x295
199 Riverneck Road		Front desk: 508-256-1300
Chelmsford, MA 01824-2820	 Facsimile: 508-256-3599

------------------------------------------------------------------------------