Re: [Qemu-devel] [PATCH v5 0/4] fdc: Use separate qdev device for drives

[John Snow <jsnow@redhat.com>]

On 10/24/2016 07:37 AM, Kevin Wolf wrote:
> 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. :-)
>
> v5:
> - Apply _filter_qemu to stderr, too [John]
> - Rename the bus to floppy-bus [Frederic]
> - Use FLOPPY_BUS() instead of DO_UPDATE() [Frederic]
>
> v4:
> - John says that his grep is broken and hangs at 100% CPU with my attempt to
>   extract the floppy controller from info qtree. Use a simpler sed command
>   instead (which, unlike the grep command, doesn't handle arbitrary indentation
>   level of the next item, but we know what comes next, so just hardcoding 10
>   spaces works, too).
>
> v3:
> - Fixed omissons in the conversion sysbus-fdc and the Sun one. Nice, combining
>   floppy controllers and weird platforms in a single series. [John]
>
> 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
>
> Alberto Garcia (2):
>   throttle: Correct access to wrong BlockBackendPublic structures
>   qemu-iotests: Test I/O in a single drive from a throttling group
>
> Halil Pasic (1):
>   block: improve error handling in raw_open
>
> Pino Toscano (1):
>   qapi: fix memory leak in bdrv_image_info_specific_dump
>

uhhh

http://i.imgur.com/60YQvmg.png

>  block/qapi.c               |  1 +
>  block/raw-posix.c          |  1 +
>  block/raw-win32.c          |  1 +
>  block/throttle-groups.c    | 27 +++++++++++++++++++++++----
>  tests/qemu-iotests/093     | 33 ++++++++++++++++++++++++++++-----
>  tests/qemu-iotests/093.out |  4 ++--
>  6 files changed, 56 insertions(+), 11 deletions(-)
>