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14 Often I've been asked which command line options the Linux/m68k
15 kernel understands, or how the exact syntax for the ... option is, or
16 ... about the option ... . I hope, this document supplies all the
20 incomplete or missing. Please update the information and send in the
24 1) Overview of the Kernel's Option Processing
34 follows: If the option is known to the kernel itself, i.e. if the name
35 (the part before the '=') or, in some cases, the whole argument string
36 is known to the kernel, it belongs to class 1. Otherwise, if the
37 argument contains an '=', it is of class 2, and the definition is put
41 This document describes the valid kernel options for Linux/m68k in
42 the version mentioned at the start of this file. Later revisions may
45 In general, the value (the part after the '=') of an option is a
47 is up to the driver that "owns" the option. This association of
48 options with drivers is also the reason that some are further
61 This tells the kernel which device it should mount as the root
65 The first syntax gives the device by name. These names are converted
66 into a major/minor number internally in the kernel in an unusual way.
67 Normally, this "conversion" is done by the device files in /dev, but
68 this isn't possible here, because the root filesystem (with /dev)
69 isn't mounted yet... So the kernel parses the name itself, with some
84 The name must be followed by a decimal number, that stands for the
85 partition number. Internally, the value of the number is just
86 added to the device number mentioned in the table above. The
88 initial ramdisk loaded by your bootstrap program (please consult the
91 /dev/ram as the root device if you want to boot from an initial
92 ramdisk. For the floppy devices, /dev/fd, the number stands for the
94 /dev/fd0 stands for the first drive, /dev/fd1 for the second, and so
95 on. Since the number is just added, you can also force the disk format
97 directory, use can see the /dev/fd0D720 has major 2 and minor 16. You
98 can specify this device for the root FS by writing "root=/dev/fd16" on
99 the kernel command line.
106 you cannot use this name for specifying the root device, because the
107 kernel cannot see this symlink before mounting the root FS and it
108 isn't in the table above. If you use it, the root device will not be
110 partition on e.g. the sixth SCSI disk as the root filesystem, if you
111 want to specify it by name. This is, because only the devices up to
112 /dev/sde are in the table above, but not /dev/sdf. Although, you can
113 use the sixth SCSI disk for the root FS, but you have to specify the
114 device by number... (see below). Or, even more strange, you can use the
115 fact that there is no range checking of the partition number, and your
121 If the device containing your root partition isn't in the table
124 have a CD with contents appropriate as a root filesystem in the first
126 decimal 11 is the major of SCSI CD-ROMs, and the minor 0 stands for
127 the first of these. You can find out all valid major numbers by
130 In addition to major and minor numbers, if the device containing your
134 possible to reference another partition on the same device using a
135 known partition UUID as the starting point. For example,
136 if partition 5 of the device has the UUID of
151 These two options tell the kernel whether it should mount the root
161 This raises the kernel log level to 10 (the default is 7). This is the
162 same level as set by the "dmesg" command, just that the maximum level
171 This option causes certain kernel messages be printed to the selected
172 debugging device. This can aid debugging the kernel, since the
174 devices are possible depends on the machine type. There are no checks
175 for the validity of the device name. If the device isn't implemented,
181 the log level is 8 or more (their level doesn't matter). Before stack
182 dumps, the kernel sets the log level to 10 automatically. A level of
183 at least 8 can also be set by the "debug" command line option (see
189 - "mem": Save the messages to a reserved area in chip mem. After
190 rebooting, they can be read under AmigaOS with the tool
201 The printing routine for this implements a timeout for the
202 case there's no printer connected (else the kernel would
212 This option instructs the kernel to set up a ramdisk of the given
213 size in KBytes. Do not use this option if the ramdisk contents are
214 passed by bootstrap! In this case, the size is selected automatically
218 should be loaded into memory. To do that, select the corresponding
219 size of the disk as ramdisk size, and set the root device to the disk
238 <dev-name> is the name of a net driver, as specified in
239 drivers/net/Space.c in the Linux source. Most prominent are eth0, ...
242 The non-ethernet drivers (sl, ppp, dummy, lo) obviously ignore the
243 settings by this options. Also, the existing ethernet drivers for
245 are really Plug-'n-Play, so the "ether=" option is useless altogether
254 This option sets the disk geometry of an IDE disk. The first hd=
255 option is for the first IDE disk, the second for the second one.
257 to use this option, since the kernel can obtain the geometry data
258 itself. It exists just for the case that this fails for one of your
267 Sets the maximum number of LUNs (logical units) of SCSI devices to
269 "Probe all LUNs on each SCSI device" was selected during the kernel
278 Sets several parameters of the SCSI tape driver. <buffer_size> is
279 the number of 512-byte buffers reserved for tape operations for each
280 device. <write_thres> sets the number of blocks which must be filled
281 to start an actual write operation to the tape. Maximum value is the
282 total number of buffers. <max_buffer> limits the total number of
291 This option controls some configurations of the Linux/m68k DMA sound
292 driver (Amiga and Atari): <buffers> is the number of buffers you want
293 to use (minimum 4, default 4), <buffer-size> is the size of each
297 AU-Files on the Falcon with its hardware frequency of 8195Hz and thus
298 don't need to expand the sound.
310 The <fbname> parameter specifies the name of the frame buffer,
312 <sub-options> is a comma-separated list of the sub-options listed
316 `video' during the development of the 1.3.x kernels, thus you
320 NBB: The behavior of video= was changed in 2.1.57 so the recommended
321 option is to specify the name of the frame buffer.
326 This sub-option may be any of the predefined video modes, as listed
327 in atari/atafb.c in the Linux/m68k source tree. The kernel will
328 activate the given video mode at boot time and make it the default
329 mode, if the hardware allows. Currently defined names are:
344 If no video mode is given on the command line, the kernel tries the
345 modes names "default<n>" in turn, until one is possible with the
348 A video mode setting doesn't make sense, if the external driver is
354 Invert the display. This affects both, text (consoles) and graphics
355 (X) display. Usually, the background is chosen to be black. With this
356 option, you can make the background white.
363 Specify the font to use in text modes. Currently you can choose only
364 between `VGA8x8', `VGA8x16' and `PEARL8x8'. `VGA8x8' is default, if the
365 vertical size of the display is less than 400 pixel rows. Otherwise, the
366 `VGA8x16' font is the default.
374 speeding up the scrolling ("hardware scrolling"). Hardware scrolling
375 is possible only if the kernel can set the video base address in steps
377 possible with plain STs and graphics cards (The former because the
378 base address must be on a 256 byte boundary there, the latter because
379 the kernel doesn't know how to set the base address at all.)
381 By default, <n> is set to the number of visible text lines on the
382 display. Thus, the amount of video memory is doubled, compared to no
383 hardware scrolling. You can turn off the hardware scrolling altogether
391 This option specifies the capabilities of some extended internal video
392 hardware, like e.g. OverScan. <xres> and <yres> give the (extended)
393 dimensions of the screen.
395 If your OverScan needs a black border, you have to write the last
396 three arguments of the "internal:". <xres_max> is the maximum line
397 length the hardware allows, <yres_max> the maximum number of lines.
398 <offset> is the offset of the visible part of the screen memory to its
402 For this, see the "sw_*" options below.
413 This is probably the most complicated parameter... It specifies that
415 use it under Linux/m68k. The kernel cannot know more about the hardware
422 <yres> and <depth> give the dimensions of the screen and the number of
423 planes (depth). The depth is the logarithm to base 2 of the number
424 of colors possible. (Or, the other way round: The number of colors is
427 You have to tell the kernel furthermore how the video memory is
431 'i': "interleaved planes", i.e. 16 bit of the first plane, than 16 bit
432 of the next, and so on... This mode is used only with the
436 planes of one pixel; this is the most common mode for 8 planes
441 For monochrome modes (i.e., <depth> is 1), the <org> letter has a
447 The next important information about the video hardware is the base
448 address of the video memory. That is given in the <scrmem> parameter,
450 address in the documentation of your hardware.
452 The next parameter, <scrlen>, tells the kernel about the size of the
453 video memory. If it's missing, the size is calculated from <xres>,
456 with the external driver, because the kernel cannot set the video base
457 address), or for virtual resolutions under X (which the X server
459 empty, either by ending the "external:" after the video address or by
463 The <vgabase> parameter is optional. If it is not given, the kernel
464 cannot read or write any color registers of the video hardware, and
466 your card is somehow VGA compatible, you can tell the kernel the base
467 address of the VGA register set, so it can change the color lookup
469 To avoid misunderstandings: <vgabase> is the _base_ address, i.e. a 4k
470 aligned address. For read/writing the color registers, the kernel
471 uses the addresses vgabase+0x3c7...vgabase+0x3c9. The <vgabase>
475 <colw> is meaningful only if <vgabase> is specified. It tells the
476 kernel how wide each of the color register is, i.e. the number of bits
480 Also <coltype> is used together with <vgabase>. It tells the kernel
481 about the color register model of your gfx board. Currently, the types
482 "vga" (which is also the default) and "mv300" (SANG MV300) are
486 the physical linelength differs from the visible length. With ProMST,
487 xres_virtual must be set to 2048. For ET4000, xres_virtual depends on the
488 initialisation of the video-card.
489 If you're missing a corresponding yres_virtual: the external part is legacy,
496 The external pixel clock attached to the Falcon VIDEL shifter. This
497 currently works only with the ScreenWonder!
504 This describes the capabilities of a multisync monitor. Don't use it
505 with a fixed-frequency monitor! For now, only the Falcon frame buffer
506 uses the settings of "monitorcap:".
508 <vmin> and <vmax> are the minimum and maximum, resp., vertical frequencies
509 your monitor can work with, in Hz. <hmin> and <hmax> are the same for
510 the horizontal frequency, in kHz.
519 If this option is given, the framebuffer device doesn't do any video
521 that does this currently is the Falcon.
524 aren't overridden by the driver, so you can still use the mode found
525 when booting, when the driver doesn't know to set this mode itself.
528 An example where you may want to use "keep" is the ScreenBlaster for
529 the Falcon.
537 With this option, you can set the mouse movement reporting threshold.
538 This is the number of pixels of mouse movement that have to accumulate
539 before the IKBD sends a new mouse packet to the kernel. Higher values
540 reduce the mouse interrupt load and thus reduce the chance of keyboard
544 You can set the threshold in x and y separately, but usually this is
545 of little practical use. If there's just one number in the option, it
558 can be selected. If you have two disk drives, select the "better"
561 The second parameter <trackbuffer> tells the kernel whether to use
563 no for the Medusa and yes for all others.
565 With the two following parameters, you can change the default
574 This option sets some parameters for the Atari native SCSI driver.
575 Generally, any number of arguments can be omitted from the end. And
576 for each of the numbers, a negative value means "use default". The
578 Below, defaults are noted as n/m, where the first value refers to
579 TT-SCSI and the latter to Falcon-SCSI. If an illegal value is given
584 This is the maximum number of SCSI commands queued internally to the
585 Atari SCSI driver. A value of 1 effectively turns off the driver
588 <cmd_per_lun> times the number of SCSI targets (LUNs) you have
592 Maximum number of SCSI commands issued to the driver for one
595 than 2 don't make sense, but waste memory. Otherwise, the maximum
596 is the number of command tags available to the driver (currently
600 The <cmd_per_lun> value at a great part determines the amount of
607 Size of the scatter-gather table, i.e. the number of requests
608 consecutive on the disk that can be merged into one SCSI command.
611 possible with the ST-DMA. Not using scatter-gather hurts
615 The SCSI ID to be used by the initiator (your Atari). This is
616 usually 7, the highest possible ID. Every ID on the SCSI bus must
617 be unique. Default: determined at run time: If the NV-RAM checksum
618 is valid, and bit 7 in byte 30 of the NV-RAM is set, the lower 3
619 bits of this byte are used as the host ID. (This method is defined
620 by Atari and also used by some TOS HD drivers.) If the above
621 isn't given, the default ID is 7. (both, TT and Falcon).
630 one LUN, and the SCSI device itself orders the requests so they
643 The <list of switches> is a comma-separated list of the following
646 ikbd: set RTS of the keyboard ACIA high
647 midi: set RTS of the MIDI ACIA high
648 snd6: set bit 6 of the PSG port A
649 snd7: set bit 6 of the PSG port A
654 as possible during kernel initialization (even before determining the
657 All of the items can also be prefixed with "ov_", i.e. "ov_ikbd",
659 video extension. The difference to the bare option is that the
661 to the HBLANK. A speciality is that ov_ikbd and ov_midi are switched
665 If you give an option both, with and without the "ov_" prefix, the
666 earlier initialization ("ov_"-less) takes precedence. But the
677 The <fbname> parameter specifies the name of the frame buffer, valid
679 that the respective frame buffer devices have been compiled into the
680 kernel (or compiled as loadable modules). The behavior of the <fbname>
684 The <sub-options> is a comma-separated list of the sub-options listed
685 below. This option is organized similar to the Atari version of the
691 Again, similar to the video mode for the Atari (see 4.1.1). Predefined
692 modes depend on the used frame buffer device.
694 OCS, ECS and AGA machines all use the color frame buffer. The following
722 Please notice that the ECS and VGA modes require either an ECS or AGA
723 chipset, and that these modes are limited to 2-bit color for the ECS
724 chipset and 8-bit color for the AGA chipset.
731 Specify the number of bit-planes for the selected video-mode.
736 Use inverted display (black on white). Functionally the same as the
737 "inverse" sub-option for the Atari.
744 Specify the font to use in text modes. Functionally the same as the
745 "font" sub-option for the Atari, except that `PEARL8x8' is used instead
746 of `VGA8x8' if the vertical size of the display is less than 400 pixel
754 This describes the capabilities of a multisync monitor. For now, only
755 the color frame buffer uses the settings of "monitorcap:".
757 <vmin> and <vmax> are the minimum and maximum, resp., vertical frequencies
758 your monitor can work with, in Hz. <hmin> and <hmax> are the same for
759 the horizontal frequency, in kHz.
769 Sets the df0 value for "silent" floppy drives. The value should be in
778 These options affect the A590/A2091, A3000 and GVP Series II SCSI
781 The <sub-options> is a comma-separated list of the sub-options listed
789 bitmask is a byte where the 1st 7 bits correspond with the 7
801 `ns' is the minimum # of nanoseconds in a SCSI data transfer
810 x = 1 does 'adaptive' disconnects, which is the default and generally
811 the best choice.
819 types of debug output to printed - see the DB_xxx defines in
829 default for the A3000 internal controller is 14, for the A2091 it's 8
830 and for the GVP hostadapters it's either 8 or 14, depending on the
831 hostadapter and the SCSI-clock jumper present on some GVP
838 than one wd33c93-based host adapter in the system.
845 If x is 1 (or if the option is just written as "nodma"), the WD33c93
846 controller will not use DMA (= direct memory access) to access the
848 A4000's with the A3640 accelerator, revision 3.0) that have problems
858 The earlier versions of the GVP driver did not handle DMA
861 running under Linux. These problems have hopefully been solved and the
867 option, please inform us about it by mailing to the Linux/68k kernel
871 valid for DMA with the GVP Series II SCSI controller. An address is
872 valid, if no bits are set except the bits that are set in the mask,
875 Some versions of the GVP can only DMA into a 24 bit address range,
876 some can address a 25 bit address range while others can use the whole
878 controller and should be autodetected by the driver. An example is the