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Date: Sun, 8 Jul 2012 21:22:17 -0400
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From: Arnaud Lacombe <lacombar@gmail.com>
To: FreeBSD Current <freebsd-current@freebsd.org>, 
	FreeBSD Hackers <freebsd-hackers@freebsd.org>
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Cc: 
Subject: newbus' ivar's limitation..
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X-List-Received-Date: Mon, 09 Jul 2012 01:22:19 -0000

Hi folks,

Ok, yet another Newbus' limitation. Assuming a device exports more
than one interface, and one of its child has need to use more than one
interface, each interfaces cannot register, concurrently, its own
ivar. While I try to always have a single child per
interface/resource, I need to keep some compatibility with the old way
of doing thing (POLA wrt. drivers I cannot/will not convert and
userland). So, it would have been nice if ivar had been per-interface,
not global and unique to one device.

Unless I am mistaken, ivar are the only way for a parent can transmit
information to a child. I can not simply implement a new METHOD to get
that ivar as the device implements multiple time the same function
(actually, up to 4 time for one, 3 for the other, with possible
crossovers...), each one physically distinct. Each child is being tied
to a pair. Thus, I need to pass each child discriminator(s) for each
interfaces right after having been *created*, which cannot be done
later on. Of course, it is out-of-question to have crossover in the
interfaces definitions.

The best way I could achieve this currently is to pass the child's
device to its parent, and do a lookup based on that pointer to get
information I need, but erk....

my 1c,
 - Arnaud