Re: [Qemu-devel] [PATCH 4/4] qmp: add BLOCK_MEDIUM_EJECT event

[Kevin Wolf]

Am 17.02.2012 12:48, schrieb Markus Armbruster:
> Kevin Wolf <address@hidden> writes:
> 
>> Am 17.02.2012 11:32, schrieb Paolo Bonzini:
>>> On 02/16/2012 03:10 PM, Luiz Capitulino wrote:
>>>> We have two external entities: the guest and the mngt app. It seems to me 
>>>> that
>>>> the guest is seeing each step at a time.
>>>
>>> The guest is seeing each step separately, but that is managed by the
>>> device model (which sends two separate error codes: a NOT READY for
>>> opening the tray, and a UNIT ATTENTION for closing the tray and changing
>>> medium) rather than by the monitor.
>>
>> But this separation isn't set in stone. Maybe it would make sense to
>> move the logic into the block layer. Of course, then it would have to
>> meet the needs of floppies as well.
> 
> And whatever other device with removable media comes up.
> 
> We should not move device-specific stuff from device models into the
> block layer.  The block layer is fat enough as it is.  And it's not
> meant for sharing code among device models.  There are better ways to do
> that.

My motivation is not sharing code but getting the model right.

As Paolo says, currently we only tell the device that the medium has
changed. It is the device's responsibility to fake separate tray
open/close events.

So my question is just if the monitor/block layer shouldn't really be
responsible for opening the tray before they change the medium and close
the tray again. This doesn't look device-specific to me at all.

But even though I think that it would be conceptionally cleaner to do it
this way, it would probably be a bad idea as faking the states requires
knowledge of when the guest has read out the intermediate status. and
only devices have this knowledge.

Kevin