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Darwin 0.2 Driver Kit

		    LogicalDisk and NXDisk notes
	
	    
r/w
   device: 	raw, block - _blockSize = dtp->d_secsize
   		live - _blockSize = physical block size
   limitations:	works on live as long as disk is formatted (checked by
			phys device)
		works on raw and block only when label valid (checked by
			NXDisk)
   effects:	faults in non-present disk (by LogicalDisk)
		
read label
   device:	raw (any partition?)
   limitations:	physDev must be formatted (checked by NXDisk)
   effects:	faults in non-present disk (by NXDisk)
   
write label
   device: 	raw (any partition?)
   limitations: physDev must be formatted (checked by NXDisk)
   		no block devices must be open (currently, maybe this won't
			work...)
   effects:	frees all block devices
   		does a _probeLabel:, possibly creating new instances
		
eject
   device:	raw
   limitations:	rejected by IODiskDevice ejectDisk if:
   			-- not removable
			-- any block devices are open
			-- physDevice and any logical disks attached
		rejected by NXDisk devEjectDisk if not raw device
   effects:	formatted = 0 by [IODiskDevice ejectDisk]
   		all block devices freed by {NXDisk devEjectDisk]
		label invalid by [NXDisk devEjectDisk]
   
set formatted
   device:	raw
   limitations:	no logical disks upstream can be open (checked in
   			IODiskDevice's setFormatted:)
   effects:	calls getPhysParams if setting formatted true
   		calls setFormattedInt - this frees all block devices and
			negates labelValid in NXDisk
   
faulting in non-present disk
   device: 	live, raw partition 0 (other raw partitions non-existent
   			when no disk present)
   limitations: none
   effects:	NXDiskProbe invoked by volCheck thread. This reads a label
   			and creates NXDisk partition instances per label info.
			volCheck thread blocks the whole time NXDiskProbe
			is running.
			
NXDiskProbe
   device:	none - NXDisk factory method, operates on physDevice
   limitations: none - called ragardless of physDev state
   effects:	AS IS:
   			creates raw device if one doesn't exist
			registerUnixDisk for both physDev and raw device
			check ready loop, init lastReadyState
			getPhysParams if newly ready
			if not formatted or not ready, done
			read a label
			if good, probeLabel:
   
probeLabel
   device:	raw
   limitations:	assumes that label is good and disk is present
   effects:	updates state of raw dev params per label
   		creates and inits one block device per partition
		
.............
Changes:

Instead of "are any logical disks upstream open" ([IOLoogicalDisk isOpen]) we really need "are any other logical disks in the chain other than me". This is for hazardous ops on the raw device like eject and setFormatted which require this to be the only open device.

IOLogicalDisk anyOtherOpen
{
	logicalDisk = [physDev logicalDisk];
	while(logicalDisk) {
		if(logicalDisk != self) {
			if([logicalDisk diskIsOpen]
				return 1;
		}
		logicalDisk = [logicalDisk logicalDisk];
	}
}
................

Just have one NXDisk instance per partition. At the NXDisk level there is almost no difference between a block device and a raw device. Change "_diskIsOpen" to "blockDevOpen" and "RawDevOpen". Sometime we only care if any block devices are open (like when writing a label or ejecting); sometimes we want to know if ANY "other" devices are open (use anyOtherOpen).
................
setting the formatted flag - current implementation is hosed.
Sould be:

   device:	NXDisk (though has to work properly on live device!)
   limitations:	no other logical disks can be open
   		no block devices can be open 
		(Both checked in [IODiskDevice setFormatted]
   effects:	invalidates label
		frees all NXDisks except for first one
		updates physParams for physDevice of setting formatted TRUE
   
/*
 * Public version for physDevice.
 */
IODiskDevice setFormatted
{
	if ANY logical disks open
		abort
	update _formatted;
   	if setting true, [self getPhysParams]
	if logicalDisk {
		[logicalDisk setFormattedInt]
	}
}

/*
 * Public version for NXDisk.
 */
NXDisk setFormatted
{
	if any block devices open
		abort
	if any other logical devices open 
		abort
	[physDev setFormattedInt]
	if setting true
		[physDev getPhysParams]
	[self setFormattedInt]
}

/*
 * Internal version for physDevice.
 */
IODiskDevice setFormattedInt
{
	update _formatted;
}

/*
 * Internal version for NXDisk.
 */
NXDisk setFormattedInt
{
	free NXDisks other than partition 0
	mark label invalid and update _formatted;
}

............

other new restrictions:

anything that blows away NXDisk instances (write label, eject, setFormatted) must be done on the 'a' partition since that's the only one which survives. I think this should be reasonable restriction....
.............

ejecting - kind of like setFormatted...

IODiskDevice ejectDisk
{
	if ANY logical disks attached
		abort
	[self devEjectDisk];	// to subclass, like SCSIDisk...
	_formatted = 0;
}

NXDisk ejectDisk
{
	if any block devices open
		abort
	if any other logical devices open 
		abort
	if this not partition 0
		abort
	[physDev devEjectDisk]
	invalidate label
	freePartitions
}

IODiskDevice devEjectDisk
{
	...implemented by subclass...
}

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