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Re: [Qemu-devel] [PATCH 2/2] fdc: Move floppy geometry guessing back fro

From: Blue Swirl
Subject: Re: [Qemu-devel] [PATCH 2/2] fdc: Move floppy geometry guessing back from block.c
Date: Tue, 19 Jun 2012 18:14:08 +0000

On Tue, Jun 19, 2012 at 7:45 AM, Markus Armbruster <address@hidden> wrote:
> Blue Swirl <address@hidden> writes:
>> On Mon, Jun 18, 2012 at 9:10 AM, Markus Armbruster <address@hidden> wrote:
>>> Commit 5bbdbb46 moved it to block.c because "other geometry guessing
>>> functions already reside in block.c".  Device-specific functionality
>>> should be kept in device code, not the block layer.  Move it back.
>> As discussed earlier, this is media specific, not device specific
>> (except FDriveType). How about media.c?
> It's floppy-(media-)specific, isn't it?
> We discussed separating floppy drive emulation (fdd) from floppy
> controller emulation.  Right now, they're mixed up in qdevs isa-fdc,
> sysbus-fdc and SUNW,fdtwo.  Separating fdd involves splitting up those
> qdevs.  I tried, but ran into QOM infrastructure difficulties.  Since
> that part of QOM is being improved, I decided to postpone the splitting
> work for a bit.
> I don't remember discussing a separation of floppy drive and floppy
> media emulation.

OK, maybe I mixed things up. How I see this is that a floppy drive may
support several different media types, like 720k, 1.44M and 2.88M
floppies, while floppy media may still be formatted differently with
various number of sectors. The media part is similar to CHS for hard
disks, while the drive or type parts are not visible outside of the HD

> Related project: moving hard disk geometry out of the block layer.
> Can't move into a device model, because we have three of them sporting
> geometry: IDE, SCSI and virtio disks.  I guess I'll move them into a new
> file in hw/.  media.c doesn't sound right for hard disks.  disk-geo.c?


> I could move floppy geometry to the same file.  But there's zero overlap
> between hard disk and floppy disk geometry, and the only consumer of
> floppy geometry is the floppy disk device.  I don't expect that to
> change, and that's why I'd prefer to make floppy geometry an
> implementation detail of the floppy disk device, and hide it in fdc.c
> now, fdd.c after the split.
> But if you insist, I can unhide it.

How about fd-geometry.c and hd-geometry.c? Or chs-translation.c to
combine both, maybe also other transformations of CHS to linear offset

> Comments?

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