[Qemu-devel] Re: [PATCH v3 06/17] qdev: Allow device specification by qtree path for device_del

[Jan Kiszka <jan.kiszka@web.de>]

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Luiz Capitulino wrote:
> On Sun, 23 May 2010 12:59:19 +0200
> Jan Kiszka <jan.kiszka@web.de> wrote:
> 
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> Allow to specify the device to be removed via device_del not only by ID
>> but also by its full or abbreviated qtree path. For this purpose,
>> qdev_find is introduced which combines walking the qtree with searching
>> for device IDs if required.
> 
>  [...]
> 
>>  Arguments:
>>  
>> -- "id": the device's ID (json-string)
>> +- "path": the device's qtree path or unique ID (json-string)
>>  
>>  Example:
>>  
>> --> { "execute": "device_del", "arguments": { "id": "net1" } }
>> +-> { "execute": "device_del", "arguments": { "path": "net1" } }
> 
>  Doesn't seem like a good change to me, besides being incompatible[1] we
> shouldn't overload arguments this way in QMP as overloading leads to
> interface degradation (harder to use, understand, maintain).

It's not overloaded, think of an ID as a (weak) symbolic link in the
qtree filesystem. The advantage of basing everything on top of full or
abbreviated qtree paths is that IDs are not always assigned, paths are.

> 
>  Maybe we could have both arguments as optional, but one must be passed.

This would at least require some way to keep the proposed unified path
specification for the human monitor (having separate arguments there is
really unhandy).

> 
> [1] It's 'legal' to break the protocol before 0.13, but this has to be
>     coordinated with libvirt so we should have a good reason to do this
> 
>>  <- { "return": {} }
>>  
>>  EQMP
> 

Jan


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