Re: [Qemu-devel] [RFC 05/10] QMP: Introduce the blockdev-tray-open command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Tue, 7 Jun 2011 18:59:12 +0530
Amit Shah <amit.shah@redhat.com> wrote:

> On (Mon) 06 Jun 2011 [11:38:03], Luiz Capitulino wrote:
> > On Mon, 6 Jun 2011 17:10:32 +0530
> > Amit Shah <amit.shah@redhat.com> wrote:
> > 
> > > On (Fri) 03 Jun 2011 [16:03:57], Luiz Capitulino wrote:
> > > 
> > > > +static int tray_open(const char *device, int remove, int force)
> > > > +{
> > > > +    BlockDriverState *bs;
> > > > +
> > > > +    bs = bdrv_removable_find(device);
> > > > +    if (!bs) {
> > > > +        return -1;
> > > > +    }
> > > > +
> > > > +    if (bdrv_eject(bs, 1, force) < 0) {
> > > > +        /* FIXME: will report undefined error in QMP */
> > > > +        return -1;
> > > > +    }
> > > > +
> > > > +    if (remove) {
> > > > +        bdrv_close(bs);
> > > > +    }
> > > > +
> > > > +    return 0;
> > > > +}
> > > 
> > > What's the reason to tie the 'remove' with tray open?
> > 
> > In my first try I had a command called 'blockdev-media-remove', but then
> > I had the impression that I was going too far as the only reason a client
> > would ever want to open the tray is to remove the media.
> 
> Not necessary -- CD/DVD writers eject and reload trays after erasing
> media -- at least they used to.

But that's not done by the VM's user/client.

I think I'll add it anyway, as it's what people seem to expect from an
API like this.

> > >  Won't it be
> > > simpler to have it separated out, perhaps a 'change' event instead of
> > > 'insert' that can accept NULL which means just remove medium?
> > 
> > You meant 'command' instead of 'event', right?
> > 
> > I don't think a change command makes sense, because it's just a shortcut
> > to open/remove/insert/close.
> 
> Yes, command, sorry.
> 
> And by 'change' I don't mean the current monitor change command --
> that's a badly-named one.
> 
> By change I mean just that -- replace the media.  And that should
> succeed only if tray is open.  And tray remains open after the change.

The same thing can be done with blockdev-media-remove and
blockdev-media-insert, so I don't think this adds value.