Date: Wed, 12 Dec 2001 21:25:24 +0100 From: Martin Heller <tracking@freebsd.mheller.org> To: current <current@FreeBSD.ORG> Subject: Re: Junior Kernel hacker task: Floppy driver mode handling. Message-ID: <3C17BD34.4050704@freebsd.mheller.org>
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Hello! After a quick glance thru the TUHS.org archives, I found a quick & dirty hack for 4.0-Stable by Jason T. Miller <jasomill@shaffstall.com> The README for this thing is as follows: >This tarball contains a dumb hack to read and write DEC RX50 diskettes >under FreeBSD. It consists of two pieces, a kernel patch and a set of >filters. The kernel patch, which should be applied to SYS/isa/fd.c, >adds >the RX50 physical format to the FreeBSD floppy driver. The patch is >based >on FreeBSD 4.0-STABLE, your mileage may vary. However, it is >conceptually >simple and should be easy enough to apply by hand. Note that this >format >is identical to the 5.25" 800K format, but with only one side. >Also in the kernel/ directory is a patch for MAKEDEV which adds device >nodes for the new format, with the name fd[n].rx50. Note that using >this >node with a drive that is not a high-density 5.25" floppy results in a >"device not configured" error. > >The filters/ directory contains two filters, rx50in and rx50out, which >deal with the logical sector interleave performed by the RQDX >controllers >on the PDP-11 and VAX; ideally, this would be handled in the driver; >like >I said, this is a dumb hack. Note that the filters read or write the >_entire_ disk; short input results in null-padding. This shouldn't be a >big deal, but it does result in a bit of extra disk I/O. C'est la vie. >They use standard input and standard output, and no output (except for >an >error message on standard error) is created if the input exceeds the >capacity of an RX50. Also keep in mind that non-PDP, non-VAX >implementations of the RX50 used different layouts, so the filters are >not >appropriate, for example, for DECmate or DEC Rainbow disks. The kernel >patch is, however, and this is the sole advantage of doing the >interleave >in userland. > >EXAMPLES: > >Create a tar archive of 'directory' on an RX50: > tar cf- directory/ | rx50out >/dev/fd1.rx50 > >Extract a tar archive from an RX50: > rx50in </dev/fd1.rx50 | tar xf- > >Finally, you can try to format a disk as an RX50 with > fdformat /dev/fd1.rx50 > >I say 'try to format' because the diskettes I format in this fashion >are >prone to read/write errors on a real RX50. This is probably due to head >alignment issues, but it could, of course, be something else. I've had >no >problems reading and writing disks formatted in other ways (by DEC or >using custom hardware, in my case a Shaffstall 6000 media conversion >unit) >Bear in mind that RX50s, though they are written at 96tpi and thus >require >a high-density drive to read and write on a PC, are _not_ a >high-density >format, and using HD media will likely result in _lots_ of errors. I >use >96tpi double-density media myself, but good luck finding it. The best >substitute that is commonly available seems to be standard 360K >double-density media without hub rings. Once again, your mileage may >vary. >Please send any questions or comments, bugfixes or patches to >jasomill@shaffstall.com; once again, this is a dumb hack, written in an >evening, full of sound and fury, signifying nothing. The code is ugly, >but >the results, I'm happy to report, are not. > >-Jason T. Miller > June 9, 2000 Hope this helps , Martin Heller To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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