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Re: [Qemu-devel] [PATCH v4 03/23] qdev: Drop ID matching from qtree path
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v4 03/23] qdev: Drop ID matching from qtree paths |
Date: |
Wed, 23 Jun 2010 13:38:17 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Jan Kiszka <address@hidden> writes:
> Markus Armbruster wrote:
>> [cc: kraxel]
>>
>> Jan Kiszka <address@hidden> writes:
>>
>>> From: Jan Kiszka <address@hidden>
>>>
>>> Device IDs may conflict with device names or aliases. From now on we
>>> only accept them outside qtree paths. This also makes dumping IDs in
>>> qbus_list_dev/bus obsolete.
>>>
>>> Signed-off-by: Jan Kiszka <address@hidden>
>>
>> I don't like this at all.
>>
>> 1. Specific problem:
>>
>> With the current code, multiple devices with the same driver work
>> only if I take care: addressing by driver name gets me only the
>> first, so I better set suitable IDs.
>>
>> With your patch, multiple devices with the same driver don't work, no
>> matter what I do.
>
> [ you already found how this is resolved ]
Yes, but I don't like that the intermediate state is broken, and I don't
like the final state.
>> 2. General principle:
>>
>> When I set an ID, I want the system to accept that ID in all contexts
>> where it makes sense. Ambiguity created by badly chosen IDs is *my*
>> problem.
>
> I disagree. IMO, QEMU should support the user to avoid such subtle
> shadowing.
IDs let me refer to my devices without having to look up ever-changing
instance numbers. This is especially relevant when I want to do refer
to buses without using (possibly ambigious) bus names.
I want to be able to say bus=scsi-ctrl.2/scsi.0 instead of
/i440FX-pcihost/pci.0/lsi53c895a.<ever-changing-number>/scsi.0
That's much more valuable to me than a well-meant attempt at protecting
me from choosing IDs badly.
Throw in multiple PCI buses, and a "no IDs in qdev paths" law becomes
even more annoying.
[Qemu-devel] [PATCH v4 06/23] qdev: Push QMP mode checks into qbus_list_bus/dev, Jan Kiszka, 2010/06/15
[Qemu-devel] [PATCH v4 05/23] qdev: Convert device and bus lists to QTAILQ, Jan Kiszka, 2010/06/15
[Qemu-devel] [PATCH v4 02/23] qdev: Restrict direct bus addressing via its name, Jan Kiszka, 2010/06/15
[Qemu-devel] [PATCH v4 08/23] qdev: Introduce qdev_iterate_recursive, Jan Kiszka, 2010/06/15
[Qemu-devel] [PATCH v4 07/23] qdev: Allow device specification by qtree path for device_del, Jan Kiszka, 2010/06/15