Re: [Qemu-devel] [PATCH v2 0/4] fdc: Use separate qdev device for drives

[Kevin Wolf <kwolf@redhat.com>]

Am 30.09.2016 um 21:39 hat Kevin Wolf geschrieben:
> We have been complaining for a long time about how the floppy controller and
> floppy drives are combined in a single qdev device and how this makes the
> device awkward to work with because it behaves different from all other block
> devices.
> 
> The latest reason to complain was when I noticed that using qdev device names
> in QMP commands (e.g. for media change) doesn't really work when only the
> controller is a qdev device, but the drives aren't.
> 
> So I decided to have a go at it, and this is the result.
> 
> It doesn't actually change any of the inner workings of the floppy controller,
> but it wires things up differently on the qdev layer so that a floppy
> controller now exposes a bus on which the floppy drives sit. This results in a
> structure that is similar to IDE where the actual drive state is still in the
> controller and the qdev device basically just contains the qdev properties -
> not pretty, but quite workable.
> 
> The commit message of patch 3 explains how to use it. In short, there is a
> '-device floppy' now and it does what you would expect if you ever used ide-cd.
> 
> The other problem is old command lines, especially those using things like
> '-global isa-fdc,driveA=...'. In order to keep them working, we need to forward
> the property to an internally created floppy drive device. This is a bit like
> usb-storage, which we know is ugly, but works well enough in practice. The good
> news here is that in contrast to usb-storage, the floppy controller only does
> the forwarding for legacy configurations; as soon as you start using '-device
> floppy', it doesn't happen any more.
> 
> So as you may have expected, this conversion doesn't result in a perfect
> device, but I think it's definitely an improvement over the old state. I hope
> you like it despite the warts. :-)
> 
> v2:
> - Added patch 4 (qemu-iotests case for floppy config on the command line)
> - Patch 2: Create a floppy device only if a BlockBackend exists instead of
>   always creating two of them
> - Patch 2: Initialise drive->fdctrl even if no drive is attached, it is
>   accessed anyway during migration
> - Patch 3: Keep 'type' qdev property and FDrive->drive in sync
> - Patch 3: Removed if with condition that is always true

ping (freeze coming closer...)