On Mon, Jun 18, 2001 at 10:47:54PM -0000, eeh@netbsd.org wrote:

 > 	With the layered device driver structure that is used extensively in
 > 	NetBSD to provide machine, bus and in some cases chip independence we
 > 	often find the following paradigm:
 > 
 > 		static void
 > 		xx_bus_attach (struct device *self, _ATTACH_ARGS_)
 > 		{
 > 			struct xx_softc *xx = (struct xx_softc *xx)self;
 > 
 > 			_DO_SOME_STUFF_
 > 
 > 			xx->xx_DATA1 = _DATA1_;
 > 			xx->xx_DATA2 = _DATA2_;
 > 			xx->xx_DATA3 = _DATA3_;
 > 			xxattach (xx, _ATTACH_ARGS_);
 > 		}
 > 
 > Once device properties are added to the kernel, this will
 > all change.  You can read about device properties in the
 > tech-kern archives.

Uh, I don't think so.

The code actually usually looks like this:

	static void
	xx_bus_attach (struct device *self, _ATTACH_ARGS_)
	{
		struct xx_softc *xx = (struct xx_softc *xx)self;

		_DO_SOME_STUFF_

		xx->xx_DATA1 = _DATA1_;
		xx->xx_DATA2 = _DATA2_;
		xx->xx_DATA3 = _DATA3_;
		xxattach (xx);
	}

Note that _DATA1_, _DATA2_, and _DATA3_ are generally derived in some
bus-specific way, but once derived, are bus-independent.  This is the
case with e.g. the DMA tag, the space tags, the space handles, etc.

Especially with the space *handles*, a bus-specific call is sometimes
required (c.f. PCI).

Getting the DMA tag might be appropriate for properties, but the space
tag fetching might have to be encapsulated inside a bus-specific call.

-- 
        -- Jason R. Thorpe <thorpej@zembu.com>