Re: [Qemu-devel] [libvirt] [PATCH 3/3] gtk: add devices menu to allow changing removable block devices

[Anthony Liguori <aliguori@us.ibm.com>]

"Daniel P. Berrange" <berrange@redhat.com> writes:

> On Thu, May 02, 2013 at 10:40:06AM -0500, Anthony Liguori wrote:
>> Kevin Wolf <kwolf@redhat.com> writes:
>> >> >> +
>> >> >> +        if (strcmp(type, "ide-cd") == 0) {
>> >> >> +            disk_type = DT_CDROM;
>> >> >> +        } else if (strcmp(type, "isa-fdc") == 0) {
>> >> >> +            disk_type = DT_FLOPPY;
>> >> >> +        } else {
>> >> >> +            disk_type = DT_NORMAL;
>> >> >> +        }
>> >> >
>> >> > Same thing here, comparing against strings is a hack. Devices should
>> >> > probably have a property that says what kind of device they are.
>> >> 
>> >> Ack, this is nasty.  I would like to eliminate this.  There is a type
>> >> field in BlockInfo but:
>> >> 
>> >> # @type: This field is returned only for compatibility reasons, it should
>> >> #        not be used (always returns 'unknown')
>> >> 
>> >> I vaguely remember this happening but I don't remember the specific
>> >> reason why.  I would definitely prefer that we filled out type
>> >> correctly.
>> >> 
>> >> I think Markus was involved in this.  Markus or Luiz, do you remember
>> >> the story here?
>> >
>> > The reason is that BlockInfo is about the backend and it simply doesn't
>> > know (ever since we introduced if=none, this was buggy, so we just
>> > abandoned it at some point). We would have to ask the device, not the
>> > block layer.
>> 
>> Yes, this makes sense.  We could introduce an interface that all disks
>> implemented that returned information about whether it was a CD-ROM,
>> Floppy, etc.
>> 
>> How does libvirt cope with this today?  I presume they do something
>> similar to what this patch is doing in terms of hard coding device
>> names.
>
> Sorry, not really sure what your question is here - how does libvirt
> cope with what exactly ?

Given a device, how do you figure out if it's a cdrom/floppy/whatever
without hard coding a mapping of class name -> device type.

Pretty sure libvirt just has a class name mapping, right?

Regards,

Anthony Liguori

>
> Daniel
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