Re: [Qemu-devel] [PATCH 2/3] QMP: Add BLOCK_MEDIA_EJECT event documentation

[Amit Shah <amit.shah@redhat.com>]

On (Mon) 30 May 2011 [16:54:22], Markus Armbruster wrote:
> Luiz Capitulino <lcapitulino@redhat.com> writes:

...

> >> The monitor command 'eject' already caused a lot of confusion, please
> >> don't make the same mistake in this event name. Even though I know more
> >> or less what eject can mean in qemu, I'm not sure what "eject" means for
> >> you in the context of this event.
> >
> > I'll change it to report the tray status instead, as suggested by Markus.
> >
> >> The 'eject' monitor command means that the image is closed and the
> >> BlockDriverState doesn't point to any image file any more. And then
> >> there's bdrv_eject(), which is what the guest can do, and it's about the
> >> virtual tray status.
> >> 
> >> Having a single event for both doesn't make sense because they are
> >> fundamentally different. Something like BLOCKDEV_CLOSE would be the
> >> right name for the 'eject' monitor command and maybe something like
> >> BLOCKDEV_TRAY_STATUS for the other one.
> >
> > Well, there are two problems here. First, we shouldn't report something
> > like BLOCKDEV_CLOSE because closing a BlockDriverState is something
> > internal to qemu that clients/users shouldn't know about. The second
> > problem is that, unfortunately, clients do use "eject" to eject a
> > removable media. Actually it's _the_ interface available for that, so
> > not emitting the event there will probably confuse clients as much as
> > not having the event at all.
> >
> > Maybe, a better solution is to fix eject to really eject the media
> > instead of closing its BlockDriverState and drop the event from the change
> > command.
> 
> Monitor command "eject" conflates three actions: open tray, remove media
> (if any), close tray.
> 
> Monitor command "change" conflates four actions: open tray, remove media
> (if any), insert media, close tray.
> 
> Except they don't really move the tray in a guest-visible manner.  They
> teleport the media.  I figure that should be changed.

Agreed.  We should be able to report these events to clients as well
as guests.

		Amit