@node Boottime configuration, Floppy ioctls, Autodetection, Top
@chapter Configuring the floppy driver via LILO or insmod

The floppy driver is configured using the @code{floppy=} options in
LILO. These options can be typed at the boot prompt, or entered in the
LILO configuration file.

Example: If your kernel is called @code{linux-2.0}, type the following
line at the LILO boot prompt (if you have a Thinkpad):
@example
linux-2.0 floppy=thinkpad
@end example
You may also enter the following line in @file{/etc/lilo.conf}, in the description
of @code{linux-2.0}:
@example
append = "floppy=thinkpad"
@end example

Several floppy related options may be given, example:
@example
linux-2.0 floppy=daring floppy=two_fdc
append = "floppy=daring floppy=two_fdc"
@end example

If you give options both in the LILO configuration file and on the boot
prompt, the option strings of both places are concatenated, the boot
prompt options coming last. That's why there are also options to
restore the default behaviour.


If you use the floppy driver as a module, use the following syntax:
@code{insmod floppy 'floppy="@var{options}"'}. (This line may be
unreadable in the info version of this document. If so, please refer to
the printed version).

Example:
@example
insmod floppy 'floppy="daring two_fdc"'
@end example

Note that in this case @code{floppy=} should only be typed out once,
and not once for each option. You need at least modules-1.3.57 for this
method.  However, the older environment variable based syntax is still
available: 
@table @asis
@item Bourne (sh, bash, ksh, zsh) syntax:
@code{floppy="daring two_fdc" insmod floppy}
@item C-shell (csh, tcsh) syntax:
@code{setenv floppy "daring two_fdc" ; insmod floppy}
@end table

Some versions of insmod are buggy in one way or another. If you have
any problems (options not being passed correctly, segfaults during
insmod), first check whether there is a more recent version. If there
isn't, use the old method using environment variables.  Problems with
@code{insmod} happen mostly for options involving both a number and a
string, such as @code{floppy=0,4,cmos}.  Options only involving strings,
such as @code{floppy=daring} are not affected.

The floppy related options include:

@table @code
@item  floppy=daring
Tells the floppy driver that you have a well behaved floppy controller.
This allows more efficient and smoother operation, but may fail on
certain controllers.

@item floppy=0,daring
Tells the floppy driver that your floppy controller should be used
with caution.

@item floppy=one_fdc
Tells the floppy driver that you have only floppy controller (default)

@item floppy=two_fdc
@item floppy=@var{address},two_fdc
Tells the floppy driver that you have two floppy controllers. The second
floppy controller is assumed to be at @var{address}. If @var{address} is
not given, 0x370 is assumed. two_fdc is implied if you use the cmos
option with a drive of id 4 to 7.

@item floppy=thinkpad
Tells the floppy driver that you have a Thinkpad. Thinkpads use an
inverted convention for the disk change line.

@item floppy=0,thinkpad
Tells the floppy driver that you don't have a Thinkpad.


@item floppy=omnibook
@itemx floppy=nodma

Tells the floppy driver not to use DMA for data transfers.  This is
needed for instance on some HP Omnibooks, which don't have a workable
DMA channel for the floppy driver. This option is also useful if you
frequently get "Unable to allocate DMA memory" messages.  Indeed, DMA
memory needs to be continuous in physical memory, and is thus harder to
find, whereas non-DMA buffers may be allocated in virtual memory.
However, I advise against this if you have an FDC without a FIFO (8272A
or 82072). 82072A and later are OK. You also need at least a 486 to use
nodma.  If you use nodma mode, I suggest you also set the FIFO threshold
to 10 or lower, in order to limit the number of data transfer
interrupts.

@item floppy=dma
Tells the floppy driver that a workable DMA channel is available
(the default).

@item floppy=nofifo
Disables the FIFO entirely. This is needed if you get "Bus master
arbitration error" messages from your ethernet card (or from other
devices) while accessing the floppy.

@item floppy=fifo
Enables the FIFO (default)

@item floppy=@var{threshold},fifo_depth
Sets the FIFO threshold. This is mostly relevant in DMA mode. If this is
higher, the floppy driver tolerates more interrupt latency, but it
triggers more interrupts (i.e. it imposes more load on the rest of the
system). If this is lower, the interrupt latency should be lower too
(faster processor). The benefit of a lower threshold is less interrupts.

To tune the FIFO threshold, switch on over/underrun messages using
@code{floppycontrol --messages}. Then access a floppy disk. If you get a
huge amount of @code{Over/Underrun - retrying} messages, then the FIFO
threshold is too low. Try with a higher value, until you only get an
occasional over/underrun.  It is a good idea to compile the floppy
driver as a module when doing this tuning. Indeed, it allows one to try
different FIFO values without rebooting the machine for each test. Note
that you need to do @code{floppycontrol --messages} every time you
re-insert the module.

Usually, tuning the FIFO threshold should not be needed, as the default
(0xa) is reasonable.

@item floppy=@var{drive},@var{type},cmos
Sets the CMOS type of @var{drive} to @var{type}. Additionally, this
drive is allowed in the bitmask. This is useful if you have more than
two floppy drives (only two can be described in the physical CMOS), or
if your BIOS uses non-standard CMOS types. The CMOS types are:
@table @code
@item 0
unknown or not installed
@item 1
5 1/4 DD
@item 2
5 1/4 HD
@item 3
3 1/2 DD
@item 4
3 1/2 HD
@item 5
3 1/2 ED
@item 6
3 1/2 ED
@end table

Note that there are two valid types for ED drives. This is because 5 was
initially chosen to represent floppy tapes, and 6 for ED drives.  AMI
ignored this, and used 5 for ED drives. That's why the floppy driver
handles both) Setting the CMOS to 0 for the first two drives (default)
makes the floppy driver read the physical CMOS for those drives.

@item floppy=unexpected_interrupts
Print a warning message when an unexpected interrupt is received 
(default behaviour)

@item floppy=no_unexpected_interrupts
@itemx floppy=L40SX
Don't print a message when an unexpected interrupt is received. This is
needed on IBM L40SX laptops in certain video modes. (There seems to be
an interaction between video and floppy. The unexpected interrupts only
affect performance, and can safely be ignored.)

@item floppy=broken_dcl
Don't use the disk change line, but assume that the disk was changed
whenever the device node is reopened. Needed on some boxes where the
disk change line is broken or unsupported.  This should be regarded as a
stopgap measure, indeed it makes floppy operation less efficient due to
unneeded cache flushing, and slightly more unreliable. Please verify
your cable, connection and jumper settings if you have any DCL problems.
However, some older drives, and also some Laptops are known not to have
a DCL.

@item floppy=debug

Print debugging messages

@item floppy=messages

Print informational messages for some operations (disk change
notifications, warnings about over and underruns, and about
autodetection)

@item floppy=silent_dcl_clear

Uses a less noisy way to clear the disk change line (which doesn't
involve seeks). Implied by daring.


(There are other options as well, but they are considered obsolete, and
thus they are not documented here)

@end table