On Thu, 27 Jun 1996 01:29:57 -0300 (EST) 
 NetBSD <netbsd@gate.ene.UnB.br> wrote:

 > For the ISA bus, which needs it if your machine has more than 16 Megs, 
 > take a look at isadma.c. I don't think bounce buffers are needed for any 
 > other bus, at least not for EISA nor PCI.

Those are for the on-board DMA controller.  The isadma bounce buffer code 
doesn't deal with bus master cards.  The floppy controller and several 
sound cards use the on-board.  Most the 154x Adaptec card doesn't; it's a 
bus master.

 > Inverts the order of the probe according to the order of the lines in the 
 > config file. It's not much use to have lines like "sd* at scsibus?" if 
 > it's the same as playing russian roulette, i.e., depending on the version 
 > you're using sd0 will end up as sd3 and, consequently, no boot drive.

This depends greatly on the semantics of the bus.  For "direct" busses 
(eg. SCSI, PCI, EISA, Sbus, etc.), you start at the first "slot" and find 
a device ... once you've found a device (the bus attach code can tell, 
because the device can say "I'm here."), then a driver is searched for.  
So, in this case, you'll find things in natural incremental order of the bus.

For "indirect" busses (e.g. ISA, VME), you have different semantics...the 
bus has no mechanism for cards to say "I'm here", and no discrete 
"slots".  Thus, the driver is called to probe for the device.  This is 
why "indirect" busses don't support "cloning" (e.g. ed*).

The order of the "indirect" probes is dependent on the order in files.isa 
(or whatever), last I checked..

 -- save the ancient forests - http://www.bayarea.net/~thorpej/forest/ -- 
Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                               Home: 408.866.1912
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