[Coco] floppy controller update

[Chuck Youse]

On Sun, 2008-07-06 at 23:32 +0100, Phill Harvey-Smith wrote:

> Yeah that seems reasonable, IIRC stock RS/Dragondos uses a 1:4 
> interleave, and most other DOSes of that vintage also seemed to use 
> interleaving other than 1:1, which is as you say prolly what Linux is 
> laying down when formatting, which is pretty much the reason that I 
> always format CoCo/Dragon disks in the actual machine and then write 
> them in Linux, because interleave is set when formatting, linux will 
> write it correctly, however it always formats with 1:1, dunno if there 
> is a way of over-riding this tho.

As is typical of Linux, you can configure everything under the sun,
except what you need.  The format interleave is more-or-less hardcoded.
>From setup_format_params() in floppy.c:

    /* determine interleave */
    il = 1;
    if (_floppy->fmt_gap < 0x22)
        il++;

Grrrr.

I wonder if I should use the extra space in this ROM (which does nothing
but load the first 18 sectors from track 34 to $2600 and jumps to $2602)
to add a menu of random nerdlies, including a FORMAT command.  That
won't be all that useful after I finish the OS-9 drivers, though.

Or I wonder if I should patch floppy.c in Linux.  That's the sort of
thing that might even prove useful and should end up in the kernel
proper.  But Linux has gotten so big these days (code-wise and
community-wise) I don't even know who to submit the patch to.. :)

C.