Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block)

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 12 May 2011 19:12:56 +0200
Markus Armbruster <armbru@redhat.com> wrote:

> Luiz Capitulino <lcapitulino@redhat.com> writes:
> 
> > On Thu, 12 May 2011 17:05:12 +0200
> > Markus Armbruster <armbru@redhat.com> wrote:
> >
> >> Its value is unreliable: a block device used as floppy has type
> >> "floppy" if created with if=floppy, but type "hd" if created with
> >> if=none.
> >> 
> >> That's because with if=none, the type is at best a declaration of
> >> intent: the drive can be connected to any guest device.  Its type is
> >> really the guest device's business.  Reporting it here is wrong.
> >
> > It reports how the guest is using the device, right? I'd say that's what
> > users/clients are interested in knowing.
> 
> The value is *unreliable*.  It may or may not match how the guest is
> using the device.  I doubt users are interested in unreliable
> information.

Can't it be fixed? And how are users/clients supposed to find out how
the guest is using its block devices?

> > Also, we can't just drop it from QMP. We should first note it's deprecated.
> 
> Would you accept a change to the more honest value "unknown" for the
> deprecation period?

We have to avoid breaking the protocol. Changing something that has always
been reported as 'cdrom' to 'unknown' will likely cause as many as damages
as dropping the command.

The best solution I can think of is noting in the documentation that the
information is unreliable and explain what clients interested in knowing
this info should do.