floppy disk controller broken

[Jeremy Chadwick]

On Thu, Sep 18, 2008 at 08:32:50PM +0200, Michel Talon wrote:
> On Thu, Sep 18, 2008 at 06:18:45PM +0200, Oliver Fromme wrote:
> > Michel Talon wrote:
> >  > John Baldwin wrote:
> >  > > It looks like the ioctl to format a track used to never report failures from 
> >  > > the controller.  The newer driver does.  What I've done with fdformat is to 
> >  > > make it just ignore the errors in userland instead.  Try this:
> >  > > 
> >  > > Index: fdformat.c
> >  > > ===================================================================
> >  > > --- fdformat.c        (revision 183112)
> >  > > +++ fdformat.c        (working copy)
> >  > > @@ -75,8 +75,7 @@
> >  > >               f.fd_formb_secno(i) = il[i+1];
> >  > >               f.fd_formb_secsize(i) = secsize;
> >  > >       }
> >  > > -     if(ioctl(fd, FD_FORM, (caddr_t)&f) < 0)
> >  > > -             err(EX_OSERR, "ioctl(FD_FORM)");
> >  > > +     (void)ioctl(fd, FD_FORM, (caddr_t)&f);
> >  > >  }
> >  > >  
> >  > >  static int
> >  > 
> >  > This doesn't work any more. This time i get 
> >  > niobe# fdformat fd0
> >  > Format 1440K floppy `/dev/fd0'? (y/n): y
> >  > Processing EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE done.
> >  > 
> >  > where only the first E takes some time to be printed, and all subsequent
> >  > ones are printed instantaneously, that is all other formatting is not
> >  > tried. In principle the formatting process must try each of the
> >  > "sectors" in turn, and can come up with a series of V and F.
> >  > 
> >  > Moreover, trying to write to the floppy:
> >  > niobe# dd if=/dev/zero of=/dev/fd0 conv=noerror
> >  > dd: /dev/fd0: Input/output error
> >  > 5+0 records in
> >  > 4+0 records out
> >  > 2048 bytes transferred in 4.054404 secs (505 bytes/sec)
> >  > 
> >  > I don't expect such result. Traditionnally writing works, while reading
> >  > may fail.
> > 
> > Maybe I misunderstand what you're saying, but ...
> > When I try to write to a floppy that has *not* been
> > successfully formatted, I very much expect to get
> > Input/output error.  Anything else would be a bug.
> > 
> > Best regards
> >    Oliver
> 
> The floppy has certainly be formatted, in the past. Perhaps i
> remember badly, i have not used floppies since years, but
> in this case the behavior with Windows, Linux and ancient FreeBSD
> was that you could write to the floppy, but could encounter errors
> while reading. Using dd conv=noerror allowed to recover the valid part.
> Under Windows you could very well use floppies partly damaged with
> bad blocks or tracks. Here the driver seems to bail out at the first
> error, so that the above commands run much faster than they should,
> a few seconds, while something of the order of a minute should be
> more realistic. 

I swore in older FreeBSD (2.x days?) there was a command which was
actually used for dealing with bad sectors on floppy disks.  I might
be thinking of badsect(8), can't remember...

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |