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Re: [Qemu-devel] [PATCH 0/3] fdc: Use separate qdev device for drives


From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH 0/3] fdc: Use separate qdev device for drives
Date: Thu, 29 Sep 2016 17:40:43 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

Am 05.09.2016 um 17:43 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. :-)
> 
> Kevin Wolf (3):
>   fdc: Add a floppy qbus
>   fdc: Add a floppy drive qdev
>   fdc: Move qdev properties to FloppyDrive
> 
>  hw/block/fdc.c | 255 
> +++++++++++++++++++++++++++++++++++++++++++++++----------
>  vl.c           |   1 +
>  2 files changed, 211 insertions(+), 45 deletions(-)

Ping?

This series really isn't as scary as one may think when looking only at
the subject lines.

Kevin



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