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

[Kevin Wolf <kwolf@redhat.com>]

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

Kevin Wolf (4):
  fdc: Add a floppy qbus
  fdc: Add a floppy drive qdev
  fdc: Move qdev properties to FloppyDrive
  qemu-iotests: Test creating floppy drives

 hw/block/fdc.c             |  263 ++++++++--
 tests/qemu-iotests/172     |  242 +++++++++
 tests/qemu-iotests/172.out | 1205 ++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/group   |    1 +
 vl.c                       |    1 +
 5 files changed, 1668 insertions(+), 44 deletions(-)
 create mode 100755 tests/qemu-iotests/172
 create mode 100644 tests/qemu-iotests/172.out

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1.8.3.1