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Re: [Qemu-devel] How to correctly use more than 2 floppy drives?
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] How to correctly use more than 2 floppy drives? |
Date: |
Fri, 5 Apr 2019 11:53:27 +0100 |
User-agent: |
Mutt/1.11.4 (2019-03-13) |
* Philippe Mathieu-Daudé (address@hidden) wrote:
> Hi,
>
> I am trying to understand the possible values for the MAX_FD variable
> used by the floppy controller model (hw/block/fdc.c).
>
> Looking at git history:
>
> - 2004-01-05 7138fcfbf7dd + 8977f3c107ef (Jocelyn Mayer):
> FDC introduced with "#define MAX_FD 2"
>
> - 2008-04-29 78ae820cfeb0 (Hervé Poussineau):
> Supports up to 4 floppy drives if MAX_FD is set to 4
> Migration stream knows about runtime value of MAX_FD
>
> - 2009-09-10 d7a6c2703577 (Juan Quintela):
> FDC vmstate-ified
> Migration stream use compile time value of MAX_FD
>
> Since 7138fcfbf7dd MAX_FD has always been defined as 2.
>
> Since d7a6c2703577 MAX_FD can not be different than 2 without breaking
> migration.
>
> If I understand correctly migration, first we should change in
> vmstate_fdc the user-definable MAX_FD by a constant 2 value.
Right.
> Then to be able to use >2 floppy disks I have to modify the the
> vmstate.version_id, and
>
> 1/ add a new field in the vmstate_fdc containing the number of drives
> and add code to check >2 and adapt
>
> or
>
> 2/ change MAX_FD to 4 for all the codebase, adding some code to migrate
> to older FDC with only 2 disks...
Or, you add a subsection which is conditional on MAX_FD > 2 and which
only stores the state of the extra FDs.
> Another option I don't like is:
>
> 3/ get ride of MAX_FD != 2 and clean the codebase...
Seems sane to me.
> $ git grep '#if MAX_FD'
> hw/block/fdc.c:744:#if MAX_FD == 4
> hw/block/fdc.c:758:#if MAX_FD == 4
> hw/block/fdc.c:1317:#if MAX_FD == 4
> hw/block/fdc.c:1340:#if MAX_FD == 4
> hw/block/fdc.c:2041:#if MAX_FD == 4
> hw/block/fdc.c:2079:#if MAX_FD == 4
> hw/block/fdc.c:2104:#if MAX_FD == 4
>
> Hervé, what board are/were you using with 4 floppy drives?
>
> BTW this link is somehow interesting :)
> https://www.seasip.info/VintagePC/floppies.html
Ah interesting; I did wonder because I've never seen machines
with more than 2 (double sided) drives.
Dave
> Thanks,
>
> Phil.
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK