Re: [Qemu-devel] [PATCH v1 1/2] qdev-monitor.c: Register reset function if the device has one

[Alistair Francis]

On Fri, Feb 19, 2016 at 9:15 AM, Andreas Färber <address@hidden> wrote:
> Am 18.02.2016 um 10:56 schrieb Markus Armbruster:
>> Alistair Francis <address@hidden> writes:
>>
>>> If the device being added when running qdev_device_add() has
>>> a reset function, register it so that it can be called.
>>>
>>> Signed-off-by: Alistair Francis <address@hidden>
>>> ---
>>>
>>>  qdev-monitor.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/qdev-monitor.c b/qdev-monitor.c
>>> index 81e3ff3..0a99d01 100644
>>> --- a/qdev-monitor.c
>>> +++ b/qdev-monitor.c
>>> @@ -561,6 +561,8 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error 
>>> **errp)
>>>
>>>      if (bus) {
>>>          qdev_set_parent_bus(dev, bus);
>>> +    } else if (dc->reset) {
>>> +        qemu_register_reset((void (*)(void *))dc->reset, dev);
>>>      }
>>>
>>>      id = qemu_opts_id(opts);
>>
>> This looks wrong to me.
>>
>> You stuff all the device reset methods into the global reset_handlers
>> list, where they get called in some semi-random order.  This breaks when
>> there are reset order dependencies between devices, e.g. between a
>> device and the bus it plugs into.
>>
>> Propagating the reset signal to all the devices is a qdev problem.
>> Copying Andreas for further insight.
>
> We had a similar discussion for s390x, and I had started a big reset
> refactoring, but we agreed to go for a stop-gap solution for 2.5. The
> recently posted hw/core/bus.c refactoring originated from that branch.
>
> The overall idea was that for buses reset propagates along buses (so
> yes, NACK to this patch), but where no bus exists it shall propagate to
> QOM children, too.
>
> So Alistair, if you have a device that needs a reset while not sitting
> on a bus, please register the register hook in your device's realize
> hook for now.

Ok, that is fair. I have moved the reset register/unregister to the
realise/unrealise functions in V2.

Thanks,

Alistair

>
> Regards,
> Andreas
>
> --
> SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Felix Imendörffer, Jane Smithard, Graham Norton; HRB 21284 (AG Nürnberg)
>