Re: [Qemu-devel] [RESEND][PATCH 3/9] microdrive: qdevify

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

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On 2011-05-17 03:38, andrzej zaborowski wrote:
> On 16 May 2011 15:08, Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> wrote:
>> On 5/16/11, andrzej zaborowski <balrogg@gmail.com> wrote:
>>> On 16 May 2011 06:54, Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> wrote:
>>>> Socket is required, as we have to know the QBus before creating the
>>>> device on it.
>>>
>>> Let's skip the qbusification then.  It seems that qbus is a wrong
>>> choice for pcmcia and there are no new features or bugs fixed by the
>>> conversion, it's code motion?  I also don't see why the socket
>>> structure should be needed at the creation time of a PCI device for
>>> example, the BusInfo should be enough logically.
>>
>> Major point for qbus'ification was ability to create PCMCIA devices from
>> command line/via other management tools. This would also allow us e.g.
>> to move microdrive driver to common ide parts, etc.
> 
> That would be nice but it may be better to use separate command line
> switches / monitor commands for hotpluggable busses.
> 
>>
>> For creation of a DeviceState via qdev_create you need BusState (which
>> is a part of PCMCIASocket). Of course I can make one global QBus for
>> all PCMCIA devices and make some artificial hacks to attach/detach cards
>> to artificial sockets, but this seems like a hack.
> 
> I considered that for a moment too but it's uglier than current code
> and doesn't achieve what you want, because the command line has no
> provision for triggering attachment.  A major problem with qdev I see
> now is that the creation and attachment of a device are one event
> instead of two, which is the case for pcmcia.  So your patch tries to
> merge these two events.

What is the point of allowing the existence of unattached pcmcia
devices? I think there was similar discussion about usb to allow attach
detach without delete, but IIRC that was finally rejected as there is no
real benefit in avoiding full creation/destruction.

Keep in mind that there may be a day where we finally obsolete support
for non-qdev (or whatever it's name will be then) devices. Every device
needs to be discoverable for QEMU in a generic way, e.g. to decide if
there are devices attached that do not support save/restore or to
explore its state. Rejecting a qdev conversion looks a bit strange from
that perspective.

Jan


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