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Date: Fri, 04 Nov 2011 11:53:53 +0100
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Subject: Re: [Qemu-devel] [PATCH] qmp: report TRAY_STATE_CHANGED events
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To: qemu-devel <qemu-devel@nongnu.org>, ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>

On 11/01/2011 06:03 AM, ShaoHe Feng wrote:
> after the guest startups, then I right click mouse in the UI of the
> guest,  and select the Eject from the menu.
> there comes an event in the qmp-monitor.
> {"timestamp": {"seconds": 1320118137, "microseconds": 420150}, "event":
> "TRAY_STATE_CHANGED", "data": {"device": "ide0-cd1", "state": "open"}}
>
> however, if I change the cdrom by this command:
> { "execute": "change","arguments": { "device": "ide0-cd1", "target":
> "/home/fsh/image/OCDC-natty-Test-Drive-20110823_010339.iso" } }
> there is no any event.
> and { "execute": "eject", "arguments": { "device": "ide0-cd1" } },
> there is also no any event.

This was by design.  The idea was that management can do the following 
to change a CD when the guest keeps the medium locked and reacts to 
eject requests (like very recent Linux does):

Scenario 1: non-forced media change

      1. start looking at TRAY_STATE_CHANGED events
      2. execute "eject" command
      3. execute "query-block"
      4. if disk is still shown as closed, check for guest reactions:
         4.1. if no TRAY_STATE_CHANGED event has been reported since
              step 1, wait until a TRAY_STATE_CHANGED event has arrived
         4.2. if the TRAY_STATE_CHANGED event had state == closed, fail
      5. execute "change" command

Scenario 2: forced media change

      1. execute "eject -f" command (with the posted patches that
         always unlock the tray upon "eject -f")
      2. execute "change" command
      3. if it fails, restart

Paolo