README and FAQ for the fla driver.
==================================
[0] COPYRIGHT & LICENSE
Please read the COPYRIGHT file carefully. If you cannot
agree to be bound by the terms of this license, please
contact M-systems and make arrangements with them.
[1] What does this driver do ?
This driver supports up to eight M-systems DiskOnChip
devices.
The driver has been tested with the following devices:
DiskOnChip2000 (8, 12, 24, 32, 40, 72, 144 MB)
DiskOnChipMillenium (8 MB)
DiskOnChipMillenium TSOP (8 MB)
You can find full details, specs etc on M-systems homepage:
http://www.m-sys.com
[2] Which firmware version ?
The driver has only been tested with version 1.21.
[3] How many devices ?
The driver supports up to 8 devices but have been tested only
with 5 due to hardware limitations in my test setup.
[4] Which FreeBSD versions ?
The driver is tested for 4.0-CURRENT and 3.3-RELEASE.
Porting to earlier versions of FreeBSD should be a simple
matter of modifying the fla.c file. [patches are welcome]
[5] Can I install FreeBSD with sysinstall ?
Yes, it has been tested in FreeBSD-4.0-CURRENT and it works.
You will need to build a kernel with the fla driver since
the default "GENERIC" kernel doesn't contain the fla driver.
[6] How to boot from a fla device ?
FreeBSD 4.0 and forward find their root device by reading
the /etc/fstab, so the DiskOnChip devices will work just
like any other device.
Earlier FreeBSD kernels recognizes the root device using
various hacks. These hacks doesn't recognize the fla device
so some "real" hacks are needed to boot from your fla
device.
In pre 4.0 versions specifying the boot device in the kernel
config file this way is the easiest way to do it:
config kernel root on major 28 minor 65538
[7] How to disklabel a fla device ?
Look at the script in prep.fla.sh, it will do the job for you.
[8] Who to contact ?
doc2k@phk.freebsd.dk will offer limited best-effort help
to the extent time permits. Further support for special
projects or configurations available at reasonable hourly
rates.
[9] Getting detailed
The DiskOnChip product gets out in some odd corners of the
PC-architecture, and chances are that things don't do what
you expect. Here are some hints and random observations
I've made during my work with these devices.
[9a] Choosing an address for the DOC
Each DOC needs a 8K memory window starting on an 8K boundary.
The lowest possible address is C000:0, the highest is DE00:0
If your hardware puts the DOC another place, you will need
to modify the doc2k_probe() call in fla.c.
It is important that you set the BIOS to not do "fancy things"
with this window, in particular no kind of cache or shadowing
can be enabled.
Be aware that some hardware will decode a 32k memory window
for the DOC device.
If everything is OK, the DOC will print a message during
the BIOS startup.
For large devices it can take some time to check the flash
data structures, but if it takes more than 3 minutes
something is wrong.
If you boot a MSDOS floppy and run FDISK you should be able
to see the DOC device.
If it doesnt work:
If you machine never gets to the point where it will boot,
but just hangs it could be because you have a BIOS which
need the "slightly special" DOC firmware. Obviously you
will need to put the DOC in another machine to load this
firmware. You can download the firmware and utilities
from M-systems website http://www.m-sys.com
If the machine boots, but the device isn't visible it can
be because some other device uses the same memory window,
or because the BIOS prevents it from being used. If you
boot MSDOS and enter DEBUG, you should be able to find a
BIOS extension signature at the address using the 'd'
command, for instance 'd d800:0'.
A special case is when the DOC prints the BIOS message
but disappears afterwards, this can happen because another
card (NCR SCSI controllers for instance) steal the memory
window later in the boot process. In such a case the
above check with DEBUG will not show the BIOS signature.
[9b] So just who is drive 'C' here anyway ?
Using the DUPDATE program you can choose to have the DOC
add itself at the front or the back of the device list.
This is, unfortunately not the only thing affecting the
drive order, the above mentioned NCR SCSI controllers also
have some builtin AI, and the result can be very confusing
because the DOC will come before even the floppy as a result.
There is no simple solution for this case, only variuos
work-arounds. But chances are good that most users will
not use both a DOC and a SCSI in the same system, except
maybe for initial programming.
[9c] MBR/fdisk
The boot firmware in the DOC and/or the FreeBSD bootblocks
mandate that the first MBR slice/(partition in FDISK lingo)
start exactly at "sector #1, head #1, cylinder #0." You
will have problems booting from the fla if you don't get this
right. The prep.fla.sh script will do this for you.
DO NOT WRITE JUNK IN THE MBR! The DOC firmware relies on
various fields and can get utterly confused if they don't
make sense.
[9d] Getting the FreeBSD kernel to use the fla as root
Please see above under item 6.
[9e] I turned the machine off while it was running and now my
DOC hangs during boot/panics the machine/does weird things.
If a write operation to the DOC gets interrupted by reset
or power-failure, it can happen that the flash data structures
are left in a state the sofware cannot cope with.
Your best chance is to DUPDATE, DFORMAT the device again.
If it hangs during boot, you can use this particular dirty
trick ENTIRELY AT YOUR OWN RISK! DO NOT COMPLAIN IF THIS
DOESN'T WORK FOR YOU OR IF YOU DESTROY YOUR COMPUTER OR
DOC DEVICE DOING IT!
Jumper the DOC for an address which will not work, but which
will not interfere with the system either, C000:0 seems to
work pretty universally for this.
Boot MSDOS and rejumper the DOC for its real (working) address.
Run DUPDATE and use the /win:xxxx argument to point it at the
DOC device.
[9f] Apart from that...
...the DOC is just like any other disk, but it is silent,
has better MTBF and doesn't take up a lot of space.
[10] History
The fla driver was written by Poul-Henning Kamp <phk@FreeBSD.org>
under contract for M-systems, and using their "OSAK"
development kit.
Good Luck,
Poul-Henning
$FreeBSD$
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