target and jtag device number is used to tie a target to a jtag device.

However with jtag devices being enabled/disabled, device num no longer has
an unambigous meaning.

If we allow reordering the jtag chain, then device num becomes even
less well defined.



Here is a thought:

- define jtag device/target num to be a unique id that has nothing
to do with the ordering of targets/jtag devices
- the jtag device chain can then afterwards be reordered and have
devices enabled/disabled/added, the id of a jtag device remains
constant
- a list is maintained of all jtag devices in the system
- a list of active jtag devices is maintained(a subset of all
jtag devices)
- the active device chain is defined by enumerating the jtag id's
to be used
- jtag devices can be created and added/removed from active
chain at any time


This scheme may well be reasonably simple to implement.


The trickiest bit I see is to find and repair all places where 'num'
is not used as an id, but used to refer to "device offset 'num' in
the chain"...

-- 
Øyvind Harboe
http://www.zylin.com/zy1000.html
ARM7 ARM9 XScale Cortex
JTAG debugger and flash programmer

Free eCos workshop in Oslo October 21!
http://www.zylin.com/workshop.html
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