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[Qemu-devel] Re: [PATCH 1/8] qdev: Allow device addressing via 'driver.i

From: Juan Quintela
Subject: [Qemu-devel] Re: [PATCH 1/8] qdev: Allow device addressing via 'driver.instance'
Date: Tue, 18 May 2010 14:38:49 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux)

Gerd Hoffmann <address@hidden> wrote:
> On 05/18/10 14:15, Markus Armbruster wrote:
>> Jan Kiszka<address@hidden>  writes:
>>> Extend qbus_find_dev to allow addressing of devices without an unique id
>>> via an optional instance number. The new formats are 'driver.instance'
>>> and 'alias.instance'.
>>> Signed-off-by: Jan Kiszka<address@hidden>
>> How's the instance number defined?  Should be documented.
> savevm instance id, used to identify multiple instances of some device
> on loadvm.  By default is just incrementing (0,1,2,...) for each new
> device instance I think.  Drivers can also specify one.  Most don't do
> that.  IIRC some ISA drivers use the base ioport as instance id, which
> sort-of makes sense as it makes sure the id identifies the correct
> device no matter what the initialization order is.
> It probably makes sense to replace the instance id with the device
> path once all devices are converted over to qdev+vmstate, so we avoid
> the nasty ordering issues altogether.

Agreed.  The problem here is that we sent the instance_id on the wire,
so for "legacy" devices that used an instance_id != -1, we are stuck
with it :(

Guess why a friend calls "backwards compatibility": A Curse of Bible
proportions :(

Later, Juan.

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