Root/Documentation/blockdev/floppy.txt

1This file describes the floppy driver.
2
3FAQ list:
4=========
5
6 A FAQ list may be found in the fdutils package (see below), and also
7at <http://fdutils.linux.lu/faq.html>.
8
9
10LILO configuration options (Thinkpad users, read this)
11======================================================
12
13 The floppy driver is configured using the 'floppy=' option in
14lilo. This option can be typed at the boot prompt, or entered in the
15lilo configuration file.
16
17 Example: If your kernel is called linux-2.6.9, type the following line
18at the lilo boot prompt (if you have a thinkpad):
19
20 linux-2.6.9 floppy=thinkpad
21
22You may also enter the following line in /etc/lilo.conf, in the description
23of linux-2.6.9:
24
25 append = "floppy=thinkpad"
26
27 Several floppy related options may be given, example:
28
29 linux-2.6.9 floppy=daring floppy=two_fdc
30 append = "floppy=daring floppy=two_fdc"
31
32 If you give options both in the lilo config file and on the boot
33prompt, the option strings of both places are concatenated, the boot
34prompt options coming last. That's why there are also options to
35restore the default behavior.
36
37
38Module configuration options
39============================
40
41 If you use the floppy driver as a module, use the following syntax:
42modprobe floppy <options>
43
44Example:
45 modprobe floppy omnibook messages
46
47 If you need certain options enabled every time you load the floppy driver,
48you can put:
49
50 options floppy omnibook messages
51
52in /etc/modprobe.conf.
53
54
55 The floppy driver related options are:
56
57 floppy=asus_pci
58    Sets the bit mask to allow only units 0 and 1. (default)
59
60 floppy=daring
61    Tells the floppy driver that you have a well behaved floppy controller.
62    This allows more efficient and smoother operation, but may fail on
63    certain controllers. This may speed up certain operations.
64
65 floppy=0,daring
66    Tells the floppy driver that your floppy controller should be used
67    with caution.
68
69 floppy=one_fdc
70    Tells the floppy driver that you have only one floppy controller.
71    (default)
72
73 floppy=two_fdc
74 floppy=<address>,two_fdc
75    Tells the floppy driver that you have two floppy controllers.
76    The second floppy controller is assumed to be at <address>.
77    This option is not needed if the second controller is at address
78    0x370, and if you use the 'cmos' option.
79
80 floppy=thinkpad
81    Tells the floppy driver that you have a Thinkpad. Thinkpads use an
82    inverted convention for the disk change line.
83
84 floppy=0,thinkpad
85    Tells the floppy driver that you don't have a Thinkpad.
86
87 floppy=omnibook
88 floppy=nodma
89    Tells the floppy driver not to use Dma for data transfers.
90    This is needed on HP Omnibooks, which don't have a workable
91    DMA channel for the floppy driver. This option is also useful
92    if you frequently get "Unable to allocate DMA memory" messages.
93    Indeed, dma memory needs to be continuous in physical memory,
94    and is thus harder to find, whereas non-dma buffers may be
95    allocated in virtual memory. However, I advise against this if
96    you have an FDC without a FIFO (8272A or 82072). 82072A and
97    later are OK. You also need at least a 486 to use nodma.
98    If you use nodma mode, I suggest you also set the FIFO
99    threshold to 10 or lower, in order to limit the number of data
100    transfer interrupts.
101
102    If you have a FIFO-able FDC, the floppy driver automatically
103    falls back on non DMA mode if no DMA-able memory can be found.
104    If you want to avoid this, explicitly ask for 'yesdma'.
105
106 floppy=yesdma
107    Tells the floppy driver that a workable DMA channel is available.
108    (default)
109
110 floppy=nofifo
111    Disables the FIFO entirely. This is needed if you get "Bus
112    master arbitration error" messages from your Ethernet card (or
113    from other devices) while accessing the floppy.
114
115 floppy=usefifo
116    Enables the FIFO. (default)
117
118 floppy=<threshold>,fifo_depth
119    Sets the FIFO threshold. This is mostly relevant in DMA
120    mode. If this is higher, the floppy driver tolerates more
121    interrupt latency, but it triggers more interrupts (i.e. it
122    imposes more load on the rest of the system). If this is
123    lower, the interrupt latency should be lower too (faster
124    processor). The benefit of a lower threshold is less
125    interrupts.
126
127    To tune the fifo threshold, switch on over/underrun messages
128    using 'floppycontrol --messages'. Then access a floppy
129    disk. If you get a huge amount of "Over/Underrun - retrying"
130    messages, then the fifo threshold is too low. Try with a
131    higher value, until you only get an occasional Over/Underrun.
132    It is a good idea to compile the floppy driver as a module
133    when doing this tuning. Indeed, it allows to try different
134    fifo values without rebooting the machine for each test. Note
135    that you need to do 'floppycontrol --messages' every time you
136    re-insert the module.
137
138    Usually, tuning the fifo threshold should not be needed, as
139    the default (0xa) is reasonable.
140
141 floppy=<drive>,<type>,cmos
142    Sets the CMOS type of <drive> to <type>. This is mandatory if
143    you have more than two floppy drives (only two can be
144    described in the physical CMOS), or if your BIOS uses
145    non-standard CMOS types. The CMOS types are:
146
147        0 - Use the value of the physical CMOS
148        1 - 5 1/4 DD
149        2 - 5 1/4 HD
150        3 - 3 1/2 DD
151        4 - 3 1/2 HD
152        5 - 3 1/2 ED
153        6 - 3 1/2 ED
154           16 - unknown or not installed
155
156    (Note: there are two valid types for ED drives. This is because 5 was
157    initially chosen to represent floppy *tapes*, and 6 for ED drives.
158    AMI ignored this, and used 5 for ED drives. That's why the floppy
159    driver handles both.)
160
161 floppy=unexpected_interrupts
162    Print a warning message when an unexpected interrupt is received.
163    (default)
164
165 floppy=no_unexpected_interrupts
166 floppy=L40SX
167    Don't print a message when an unexpected interrupt is received. This
168    is needed on IBM L40SX laptops in certain video modes. (There seems
169    to be an interaction between video and floppy. The unexpected
170    interrupts affect only performance, and can be safely ignored.)
171
172 floppy=broken_dcl
173    Don't use the disk change line, but assume that the disk was
174    changed whenever the device node is reopened. Needed on some
175    boxes where the disk change line is broken or unsupported.
176    This should be regarded as a stopgap measure, indeed it makes
177    floppy operation less efficient due to unneeded cache
178    flushings, and slightly more unreliable. Please verify your
179    cable, connection and jumper settings if you have any DCL
180    problems. However, some older drives, and also some laptops
181    are known not to have a DCL.
182
183 floppy=debug
184    Print debugging messages.
185
186 floppy=messages
187    Print informational messages for some operations (disk change
188    notifications, warnings about over and underruns, and about
189    autodetection).
190
191 floppy=silent_dcl_clear
192    Uses a less noisy way to clear the disk change line (which
193    doesn't involve seeks). Implied by 'daring' option.
194
195 floppy=<nr>,irq
196    Sets the floppy IRQ to <nr> instead of 6.
197
198 floppy=<nr>,dma
199    Sets the floppy DMA channel to <nr> instead of 2.
200
201 floppy=slow
202    Use PS/2 stepping rate:
203     " PS/2 floppies have much slower step rates than regular floppies.
204       It's been recommended that take about 1/4 of the default speed
205       in some more extreme cases."
206
207
208Supporting utilities and additional documentation:
209==================================================
210
211 Additional parameters of the floppy driver can be configured at
212runtime. Utilities which do this can be found in the fdutils package.
213This package also contains a new version of mtools which allows to
214access high capacity disks (up to 1992K on a high density 3 1/2 disk!).
215It also contains additional documentation about the floppy driver.
216
217The latest version can be found at fdutils homepage:
218 http://fdutils.linux.lu
219
220The fdutils releases can be found at:
221 http://fdutils.linux.lu/download.html
222 http://www.tux.org/pub/knaff/fdutils/
223 ftp://metalab.unc.edu/pub/Linux/utils/disk-management/
224
225Reporting problems about the floppy driver
226==========================================
227
228 If you have a question or a bug report about the floppy driver, mail
229me at Alain.Knaff@poboxes.com . If you post to Usenet, preferably use
230comp.os.linux.hardware. As the volume in these groups is rather high,
231be sure to include the word "floppy" (or "FLOPPY") in the subject
232line. If the reported problem happens when mounting floppy disks, be
233sure to mention also the type of the filesystem in the subject line.
234
235 Be sure to read the FAQ before mailing/posting any bug reports!
236
237 Alain
238
239Changelog
240=========
241
24210-30-2004 : Cleanup, updating, add reference to module configuration.
243        James Nelson <james4765@gmail.com>
244
2456-3-2000 : Original Document
246

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