x86: add noclflush option
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / kernel-parameters.txt
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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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3
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
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20This document may not be entirely up to date and comprehensive. The command
21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22module. Loadable modules, after being loaded into the running kernel, also
23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24parameters may be changed at runtime by the command
25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
26
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27The parameters listed below are only valid if certain kernel build options were
28enabled and if respective hardware is present. The text in square brackets at
29the beginning of each description states the restrictions within which a
30parameter is applicable:
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31
32 ACPI ACPI support is enabled.
c99c108a 33 AGP AGP (Accelerated Graphics Port) is enabled.
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34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
e7ba176b 37 AVR32 AVR32 architecture is enabled.
1da177e4 38 AX25 Appropriate AX.25 support is enabled.
0ae53640 39 BLACKFIN Blackfin architecture is enabled.
a9913044 40 DRM Direct Rendering Management support is enabled.
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41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
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46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
11ef697b 52 LIBATA Libata driver is enabled
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53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
309e57df 61 MSI Message Signaled Interrupts (PCI).
c8facbb6 62 MTD MTD (Memory Technology Device) support is enabled.
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63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
734efb46 65 GENERIC_TIME The generic timeofday code is enabled.
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66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
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68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
7f785763 72 PCIE PCI Express support is enabled.
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73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
20510f2f 79 ROOTPLUG The example Root Plug LSM is enabled.
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80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
20510f2f 84 SECURITY Different security models are enabled.
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85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
e523d93c 87 SH SuperH architecture is enabled.
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88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
a9913044 90 SWSUSP Software suspend is enabled.
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91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 99 X86-32 X86-32, aka i386 architecture is enabled.
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100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
103
104In addition, the following text indicates that the option:
105
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
109
110Parameters denoted with BOOT are actually interpreted by the boot
111loader, and have no meaning to the kernel directly.
112Do not modify the syntax of boot loader parameters without extreme
113need or coordination with <Documentation/i386/boot.txt>.
114
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115There are also arch-specific kernel-parameters not documented here.
116See for example <Documentation/x86_64/boot-options.txt>.
117
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118Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119a trailing = on the name of any parameter states that that parameter will
120be entered as an environment variable, whereas its absence indicates that
121it will appear as a kernel argument readable via /proc/cmdline by programs
122running once the system is up.
123
9c4751fd 124The number of kernel parameters is not limited, but the length of the
125complete command line (parameters including spaces etc.) is limited to
126a fixed number of characters. This limit depends on the architecture
127and is between 256 and 4096 characters. It is defined in the file
128./include/asm/setup.h as COMMAND_LINE_SIZE.
129
130
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131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
a9913044 133 Format: { force | off | ht | strict | noirq }
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134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
a9913044 138 strict -- Be less tolerant of platforms that are not
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139 strictly ACPI specification compliant.
140
141 See also Documentation/pm.txt, pci=noacpi
142
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143 acpi_apic_instance= [ACPI, IOAPIC]
144 Format: <int>
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
4e381a4f 147 default: 0
a1fdcc0d 148
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149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode }
151 See Documentation/power/video.txt
a9913044 152
1da177e4 153 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 154 Format: { level | edge | high | low }
1da177e4 155
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156 acpi_irq_balance [HW,ACPI]
157 ACPI will balance active IRQs
158 default in APIC mode
1da177e4 159
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160 acpi_irq_nobalance [HW,ACPI]
161 ACPI will not move active IRQs (default)
162 default in PIC mode
1da177e4 163
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164 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
165 use by PCI
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166 Format: <irq>,<irq>...
167
a9913044 168 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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169 Format: <irq>,<irq>...
170
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171 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
172
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173 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
174 Format: To spoof as Windows 98: ="Microsoft Windows"
175
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176 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
177 acpi_osi="string1" # add string1 -- only one string
178 acpi_osi="!string2" # remove built-in string2
179 acpi_osi= # disable all strings
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180
181 acpi_serialize [HW,ACPI] force serialization of AML methods
182
183 acpi_skip_timer_override [HW,ACPI]
184 Recognize and ignore IRQ0/pin2 Interrupt Override.
185 For broken nForce2 BIOS resulting in XT-PIC timer.
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186 acpi_use_timer_override [HW,ACPI}
187 Use timer override. For some broken Nvidia NF5 boards
188 that require a timer override, but don't have
189 HPET
1da177e4 190
f989106c 191 acpi.debug_layer= [HW,ACPI]
1da177e4 192 Format: <int>
a9913044 193 Each bit of the <int> indicates an ACPI debug layer,
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194 1: enable, 0: disable. It is useful for boot time
195 debugging. After system has booted up, it can be set
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196 via /sys/module/acpi/parameters/debug_layer.
197 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
198 Available bits (add the numbers together) to enable debug output
199 for specific parts of the ACPI subsystem:
200 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
201 0x10 namespace 0x20 parser 0x40 dispatcher
202 0x80 executer 0x100 resources 0x200 acpica debugger
203 0x400 os services 0x800 acpica disassembler.
204 The number can be in decimal or prefixed with 0x in hex.
205 Warning: Many of these options can produce a lot of
206 output and make your system unusable. Be very careful.
207
208 acpi.debug_level= [HW,ACPI]
1da177e4 209 Format: <int>
a9913044 210 Each bit of the <int> indicates an ACPI debug level,
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211 1: enable, 0: disable. It is useful for boot time
212 debugging. After system has booted up, it can be set
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213 via /sys/module/acpi/parameters/debug_level.
214 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
215 Available bits (add the numbers together) to enable different
216 debug output levels of the ACPI subsystem:
217 0x01 error 0x02 warn 0x04 init 0x08 debug object
218 0x10 info 0x20 init names 0x40 parse 0x80 load
219 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
220 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
221 0x10000 resources 0x20000 user requests 0x40000 package.
222 The number can be in decimal or prefixed with 0x in hex.
223 Warning: Many of these options can produce a lot of
224 output and make your system unusable. Be very careful.
225
cd4f0ef7 226 acpi_pm_good [X86-32,X86-64]
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227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
230
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231 agp= [AGP]
232 { off | try_unsupported }
233 off: disable AGP support
234 try_unsupported: try to drive unsupported chipsets
235 (may crash computer or cause data corruption)
236
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237 enable_timer_pin_1 [i386,x86-64]
238 Enable PIN 1 of APIC timer
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239 Can be useful to work around chipset bugs
240 (in particular on some ATI chipsets).
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241 The kernel tries to set a reasonable default.
242
243 disable_timer_pin_1 [i386,x86-64]
244 Disable PIN 1 of APIC timer
245 Can be useful to work around chipset bugs.
246
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247 ad1848= [HW,OSS]
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
249
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250 advansys= [HW,SCSI]
251 See header of drivers/scsi/advansys.c.
252
253 advwdt= [HW,WDT] Advantech WDT
254 Format: <iostart>,<iostop>
255
256 aedsp16= [HW,OSS] Audio Excel DSP 16
257 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
258 See also header of sound/oss/aedsp16.c.
a9913044 259
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260 aha152x= [HW,SCSI]
261 See Documentation/scsi/aha152x.txt.
262
263 aha1542= [HW,SCSI]
264 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
265
266 aic7xxx= [HW,SCSI]
267 See Documentation/scsi/aic7xxx.txt.
268
269 aic79xx= [HW,SCSI]
270 See Documentation/scsi/aic79xx.txt.
271
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272 amijoy.map= [HW,JOY] Amiga joystick support
273 Map of devices attached to JOY0DAT and JOY1DAT
274 Format: <a>,<b>
275 See also Documentation/kernel/input/joystick.txt
276
277 analog.map= [HW,JOY] Analog joystick and gamepad support
278 Specifies type or capabilities of an analog joystick
279 connected to one of 16 gameports
280 Format: <type1>,<type2>,..<type16>
281
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282 apc= [HW,SPARC]
283 Power management functions (SPARCstation-4/5 + deriv.)
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284 Format: noidle
285 Disable APC CPU standby support. SPARCstation-Fox does
286 not play well with APC CPU idle - disable it if you have
287 APC and your system crashes randomly.
288
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289 apic= [APIC,i386] Advanced Programmable Interrupt Controller
290 Change the output verbosity whilst booting
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291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
a9913044 294
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295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
297
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298 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
299 Format: <io>,<irq>,<nodeID>
300
301 ataflop= [HW,M68k]
302
303 atarimouse= [HW,MOUSE] Atari Mouse
304
305 atascsi= [HW,SCSI] Atari SCSI
306
307 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
308 EzKey and similar keyboards
309
310 atkbd.reset= [HW] Reset keyboard during initialization
311
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312 atkbd.set= [HW] Select keyboard code set
313 Format: <int> (2 = AT (default), 3 = PS/2)
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314
315 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
316 keyboards
317
318 atkbd.softraw= [HW] Choose between synthetic and real raw mode
319 Format: <bool> (0 = real, 1 = synthetic (default))
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320
321 atkbd.softrepeat= [HW]
322 Use software keyboard repeat
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323
324 autotest [IA64]
325
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326 baycom_epp= [HW,AX25]
327 Format: <io>,<mode>
a9913044 328
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329 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
330 Format: <io>,<mode>
331 See header of drivers/net/hamradio/baycom_par.c.
332
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333 baycom_ser_fdx= [HW,AX25]
334 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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335 Format: <io>,<irq>,<mode>[,<baud>]
336 See header of drivers/net/hamradio/baycom_ser_fdx.c.
337
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338 baycom_ser_hdx= [HW,AX25]
339 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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340 Format: <io>,<irq>,<mode>
341 See header of drivers/net/hamradio/baycom_ser_hdx.c.
342
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343 boot_delay= Milliseconds to delay each printk during boot.
344 Values larger than 10 seconds (10000) are changed to
345 no delay (0).
346 Format: integer
347
1da177e4 348 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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349 bttv.radio= Most important insmod options are available as
350 kernel args too.
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351 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
352 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
353
354 BusLogic= [HW,SCSI]
355 See drivers/scsi/BusLogic.c, comment before function
356 BusLogic_ParseDriverOptions().
357
358 c101= [NET] Moxa C101 synchronous serial card
359
cd4f0ef7 360 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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361 Sometimes CPU hardware bugs make them report the cache
362 size incorrectly. The kernel will attempt work arounds
363 to fix known problems, but for some CPUs it is not
364 possible to determine what the correct size should be.
365 This option provides an override for these situations.
366
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367 capability.disable=
368 [SECURITY] Disable capabilities. This would normally
369 be used only if an alternative security model is to be
370 configured. Potentially dangerous and should only be
371 used if you are entirely sure of the consequences.
372
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373 ccw_timeout_log [S390]
374 See Documentation/s390/CommonIO for details.
375
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376 checkreqprot [SELINUX] Set initial checkreqprot flag value.
377 Format: { "0" | "1" }
378 See security/selinux/Kconfig help text.
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379 0 -- check protection applied by kernel (includes
380 any implied execute protection).
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381 1 -- check protection requested by application.
382 Default value is set via a kernel config option.
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383 Value can be changed at runtime via
384 /selinux/checkreqprot.
385
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386 cio_ignore= [S390]
387 See Documentation/s390/CommonIO for details.
388
389 cio_msg= [S390]
390 See Documentation/s390/CommonIO for details.
391
cd4f0ef7 392 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 393 [Deprecated]
3f6dee9b 394 Forces specified clocksource (if available) to be used
734efb46 395 when calculating gettimeofday(). If specified
3f6dee9b 396 clocksource is not available, it defaults to PIT.
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397 Format: { pit | tsc | cyclone | pmtmr }
398
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399 clocksource= [GENERIC_TIME] Override the default clocksource
400 Format: <string>
401 Override the default clocksource and use the clocksource
402 with the name specified.
403 Some clocksource names to choose from, depending on
404 the platform:
405 [all] jiffies (this is the base, fallback clocksource)
406 [ACPI] acpi_pm
407 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
408 pxa_timer,timer3,32k_counter,timer0_1
409 [AVR32] avr32
cd4f0ef7 410 [X86-32] pit,hpet,tsc,vmi-timer;
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411 scx200_hrt on Geode; cyclone on IBM x440
412 [MIPS] MIPS
413 [PARISC] cr16
414 [S390] tod
415 [SH] SuperH
416 [SPARC64] tick
417 [X86-64] hpet,tsc
418
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419 code_bytes [IA32/X86_64] How many bytes of object code to print
420 in an oops report.
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421 Range: 0 - 8192
422 Default: 64
423
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424 disable_8254_timer
425 enable_8254_timer
426 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
427 over the 8254 in addition to over the IO-APIC. The
428 kernel tries to set a sensible default.
429
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430 hpet= [X86-32,HPET] option to control HPET usage
431 Format: { enable (default) | disable | force }
432 disable: disable HPET and use PIT instead
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433 force: allow force enabled of undocumented chips (ICH4,
434 VIA, nVidia)
1da177e4 435
1da177e4 436 com20020= [HW,NET] ARCnet - COM20020 chipset
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437 Format:
438 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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439
440 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
441 Format: <io>[,<irq>]
442
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443 com90xx= [HW,NET]
444 ARCnet - COM90xx chipset (memory-mapped buffers)
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445 Format: <io>[,<irq>[,<memstart>]]
446
447 condev= [HW,S390] console device
448 conmode=
a9913044 449
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450 console= [KNL] Output console device and options.
451
452 tty<n> Use the virtual console device <n>.
453
454 ttyS<n>[,options]
f1a1c2dc 455 ttyUSB0[,options]
1da177e4 456 Use the specified serial port. The options are of
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457 the form "bbbbpnf", where "bbbb" is the baud rate,
458 "p" is parity ("n", "o", or "e"), "n" is number of
459 bits, and "f" is flow control ("r" for RTS or
460 omit it). Default is "9600n8".
461
462 See Documentation/serial-console.txt for more
463 information. See
464 Documentation/networking/netconsole.txt for an
465 alternative.
1da177e4 466
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467 uart[8250],io,<addr>[,options]
468 uart[8250],mmio,<addr>[,options]
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469 Start an early, polled-mode console on the 8250/16550
470 UART at the specified I/O port or MMIO address,
471 switching to the matching ttyS device later. The
472 options are the same as for ttyS, above.
473
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474 earlycon= [KNL] Output early console device and options.
475 uart[8250],io,<addr>[,options]
476 uart[8250],mmio,<addr>[,options]
477 Start an early, polled-mode console on the 8250/16550
478 UART at the specified I/O port or MMIO address.
479 The options are the same as for ttyS, above.
480
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481 no_console_suspend
482 [HW] Never suspend the console
483 Disable suspending of consoles during suspend and
484 hibernate operations. Once disabled, debugging
485 messages can reach various consoles while the rest
486 of the system is being put to sleep (ie, while
487 debugging driver suspend/resume hooks). This may
488 not work reliably with all consoles, but is known
489 to work with serial and VGA consoles.
490
1da177e4 491 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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492 Format:
493 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 494
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495 crashkernel=nn[KMG]@ss[KMG]
496 [KNL] Reserve a chunk of physical memory to
497 hold a kernel to switch to with kexec on panic.
498
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499 crashkernel=range1:size1[,range2:size2,...][@offset]
500 [KNL] Same as above, but depends on the memory
501 in the running system. The syntax of range is
502 start-[end] where start and end are both
503 a memory unit (amount[KMG]). See also
504 Documentation/kdump/kdump.txt for a example.
505
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506 cs4232= [HW,OSS]
507 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
508
509 cs89x0_dma= [HW,NET]
510 Format: <dma>
511
512 cs89x0_media= [HW,NET]
513 Format: { rj45 | aui | bnc }
a9913044 514
a9913044 515 dasd= [HW,NET]
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516 See header of drivers/s390/block/dasd_devmap.c.
517
518 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
519 (one device per port)
520 Format: <port#>,<type>
521 See also Documentation/input/joystick-parport.txt
522
523 debug [KNL] Enable kernel debugging (events log level).
524
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525 debug_locks_verbose=
526 [KNL] verbose self-tests
527 Format=<0|1>
528 Print debugging info while doing the locking API
529 self-tests.
530 We default to 0 (no extra messages), setting it to
531 1 will print _a lot_ more information - normally
532 only useful to kernel developers.
533
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534 decnet= [HW,NET]
535 Format: <area>[,<node>]
536 See also Documentation/networking/decnet.txt.
537
ecb77fa9 538 vt.default_blu= [VT]
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539 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
540 Change the default blue palette of the console.
541 This is a 16-member array composed of values
542 ranging from 0-255.
543
ecb77fa9 544 vt.default_grn= [VT]
55ff9780
AD
545 Format: <green0>,<green1>,<green2>,...,<green15>
546 Change the default green palette of the console.
547 This is a 16-member array composed of values
548 ranging from 0-255.
549
ecb77fa9 550 vt.default_red= [VT]
55ff9780
AD
551 Format: <red0>,<red1>,<red2>,...,<red15>
552 Change the default red palette of the console.
553 This is a 16-member array composed of values
554 ranging from 0-255.
555
ecb77fa9
ST
556 vt.default_utf8=
557 [VT]
55ff9780
AD
558 Format=<0|1>
559 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
560 Default is 1, i.e. UTF-8 mode is enabled for all
561 newly opened terminals.
55ff9780 562
1da177e4
LT
563 dhash_entries= [KNL]
564 Set number of hash buckets for dentry cache.
a9913044 565
1da177e4
LT
566 digi= [HW,SERIAL]
567 IO parameters + enable/disable command.
568
569 digiepca= [HW,SERIAL]
570 See drivers/char/README.epca and
571 Documentation/digiepca.txt.
572
99fc8d42
JB
573 disable_mtrr_trim [X86-64, Intel only]
574 By default the kernel will trim any uncacheable
575 memory out of your available memory pool based on
576 MTRR settings. This parameter disables that behavior,
577 possibly causing your machine to run very slowly.
578
1da177e4
LT
579 dmasound= [HW,OSS] Sound subsystem buffers
580
581 dscc4.setup= [NET]
582
583 dtc3181e= [HW,SCSI]
584
0ae53640 585 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
586 earlyprintk=vga
587 earlyprintk=serial[,ttySn[,baudrate]]
588
a9913044 589 Append ",keep" to not disable it when the real console
1da177e4
LT
590 takes over.
591
592 Only vga or serial at a time, not both.
593
594 Currently only ttyS0 and ttyS1 are supported.
595
596 Interaction with the standard serial driver is not
597 very good.
598
599 The VGA output is eventually overwritten by the real
600 console.
601
602 eata= [HW,SCSI]
603
1da177e4
LT
604 edd= [EDD]
605 Format: {"of[f]" | "sk[ipmbr]"}
606 See comment in arch/i386/boot/edd.S
607
1da177e4
LT
608 eisa_irq_edge= [PARISC,HW]
609 See header of drivers/parisc/eisa.c.
610
cd4f0ef7 611 elanfreq= [X86-32]
1da177e4
LT
612 See comment before function elanfreq_setup() in
613 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
614
615 elevator= [IOSCHED]
16ab3adf 616 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
617 See Documentation/block/as-iosched.txt and
618 Documentation/block/deadline-iosched.txt for details.
619
cd4f0ef7 620 elfcorehdr= [X86-32, X86_64]
a9913044 621 Specifies physical address of start of kernel core
aac04b32
VG
622 image elf header. Generally kexec loader will
623 pass this option to capture kernel.
624 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
625
626 enforcing [SELINUX] Set initial enforcing status.
627 Format: {"0" | "1"}
628 See security/selinux/Kconfig help text.
629 0 -- permissive (log only, no denials).
630 1 -- enforcing (deny and log).
631 Default value is 0.
632 Value can be changed at runtime via /selinux/enforce.
633
1da177e4
LT
634 es1371= [HW,OSS]
635 Format: <spdif>,[<nomix>,[<amplifier>]]
636 See also header of sound/oss/es1371.c.
a9913044 637
1da177e4
LT
638 ether= [HW,NET] Ethernet cards parameters
639 This option is obsoleted by the "netdev=" option, which
640 has equivalent usage. See its documentation for details.
641
642 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
643 Format: <io>[,<irq>]
644
de1ba09b
AM
645 failslab=
646 fail_page_alloc=
647 fail_make_request=[KNL]
648 General fault injection mechanism.
649 Format: <interval>,<probability>,<space>,<times>
650 See also /Documentation/fault-injection/.
651
1da177e4
LT
652 fd_mcs= [HW,SCSI]
653 See header of drivers/scsi/fd_mcs.c.
654
655 fdomain= [HW,SCSI]
656 See header of drivers/scsi/fdomain.c.
657
658 floppy= [HW]
659 See Documentation/floppy.txt.
660
1da177e4
LT
661 gamecon.map[2|3]=
662 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
663 support via parallel port (up to 5 devices per port)
664 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
665 See also Documentation/input/joystick-parport.txt
666
667 gamma= [HW,DRM]
668
aaf23042
YL
669 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
670 Format: off | on
671 default: on
672
1da177e4
LT
673 gdth= [HW,SCSI]
674 See header of drivers/scsi/gdth.c.
675
676 gpt [EFI] Forces disk with valid GPT signature but
677 invalid Protective MBR to be treated as GPT.
678
1da177e4
LT
679 gvp11= [HW,SCSI]
680
681 hashdist= [KNL,NUMA] Large hashes allocated during boot
682 are distributed across NUMA nodes. Defaults on
683 for IA-64, off otherwise.
a9913044 684 Format: 0 | 1 (for off | on)
1da177e4
LT
685
686 hcl= [IA-64] SGI's Hardware Graph compatibility layer
687
688 hd= [EIDE] (E)IDE hard drive subsystem geometry
689 Format: <cyl>,<head>,<sect>
690
691 hd?= [HW] (E)IDE subsystem
692 hd?lun= See Documentation/ide.txt.
693
694 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
695 size of <nn>. This works even on boxes that have no
696 highmem otherwise. This also works to reduce highmem
697 size on bigger boxes.
698
54cdfdb4
TG
699 highres= [KNL] Enable/disable high resolution timer mode.
700 Valid parameters: "on", "off"
701 Default: "on"
702
1da177e4
LT
703 hisax= [HW,ISDN]
704 See Documentation/isdn/README.HiSax.
705
cd4f0ef7 706 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
1da177e4 707
1da177e4 708 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
709 i8042.dumbkbd [HW] Pretend that controller can only read data from
710 keyboard and cannot control its state
1da177e4
LT
711 (Don't attempt to blink the leds)
712 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 713 i8042.nokbd [HW] Don't check/create keyboard port
1da177e4
LT
714 i8042.nomux [HW] Don't check presence of an active multiplexing
715 controller
716 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
717 controllers
718 i8042.panicblink=
719 [HW] Frequency with which keyboard LEDs should blink
720 when kernel panics (default is 0.5 sec)
721 i8042.reset [HW] Reset the controller during init and cleanup
722 i8042.unlock [HW] Unlock (ignore) the keylock
723
724 i810= [HW,DRM]
725
e70c9d5e
DT
726 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
727 indicates that the driver is running on unsupported
728 hardware.
1da177e4
LT
729 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
730 does not match list of supported models.
731 i8k.power_status
732 [HW] Report power status in /proc/i8k
733 (disabled by default)
734 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
735 capability is set.
736
737 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
738 See Documentation/mca.txt.
739
740 icn= [HW,ISDN]
741 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
742
743 ide= [HW] (E)IDE subsystem
744 Format: ide=nodma or ide=doubler or ide=reverse
745 See Documentation/ide.txt.
746
747 ide?= [HW] (E)IDE subsystem
748 Format: ide?=noprobe or chipset specific parameters.
749 See Documentation/ide.txt.
a9913044 750
1da177e4
LT
751 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
752 See Documentation/ide.txt.
753
f039b754
AK
754 idle= [X86]
755 Format: idle=poll or idle=mwait
756 Poll forces a polling idle loop that can slightly improves the performance
757 of waking up a idle CPU, but will use a lot of power and make the system
758 run hot. Not recommended.
759 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
760 to not use it because it doesn't save as much power as a normal idle
761 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
762 as idle=poll.
a9913044 763
79290822
IM
764 ignore_loglevel [KNL]
765 Ignore loglevel setting - this will print /all/
766 kernel messages to the console. Useful for debugging.
767
1da177e4
LT
768 ihash_entries= [KNL]
769 Set number of hash buckets for inode cache.
770
771 in2000= [HW,SCSI]
772 See header of drivers/scsi/in2000.c.
773
774 init= [KNL]
775 Format: <full_path>
776 Run specified binary instead of /sbin/init as init
777 process.
778
779 initcall_debug [KNL] Trace initcalls as they are executed. Useful
780 for working out where the kernel is dying during
781 startup.
782
783 initrd= [BOOT] Specify the location of the initial ramdisk
784
785 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
786 Format: <irq>
787
788 inttest= [IA64]
789
ba395927
KA
790 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
791 off
792 Disable intel iommu driver.
793 igfx_off [Default Off]
794 By default, gfx is mapped as normal device. If a gfx
795 device has a dedicated DMAR unit, the DMAR unit is
796 bypassed by not enabling DMAR with this option. In
797 this case, gfx device will use physical address for
798 DMA.
7d3b03ce
KA
799 forcedac [x86_64]
800 With this option iommu will not optimize to look
801 for io virtual address below 32 bit forcing dual
802 address cycle on pci bus for cards supporting greater
803 than 32 bit addressing. The default is to look
804 for translation below 32 bit and if not available
805 then look in the higher range.
ba395927 806
b02aae9c 807 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
808 0x80
809 Standard port 0x80 based delay
810 0xed
811 Alternate port 0xed based delay (needed on some systems)
b02aae9c 812 udelay
6e7c4025
IM
813 Simple two microseconds delay
814 none
815 No delay
b02aae9c 816
1da177e4
LT
817 io7= [HW] IO7 for Marvel based alpha systems
818 See comment before marvel_specify_io7 in
819 arch/alpha/kernel/core_marvel.c.
820
821 ip= [IP_PNP]
822 See Documentation/nfsroot.txt.
823
824 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
825 See comment before ip2_setup() in
826 drivers/char/ip2/ip2base.c.
1da177e4
LT
827
828 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
829 See header of drivers/scsi/ips.c.
830
72c4a13a
SH
831 ports= [IP_VS_FTP] IPVS ftp helper module
832 Default is 21.
833 Up to 8 (IP_VS_APP_MAX_PORTS) ports
834 may be specified.
835 Format: <port>,<port>....
836
200803df
AC
837 irqfixup [HW]
838 When an interrupt is not handled search all handlers
839 for it. Intended to get systems with badly broken
840 firmware running.
841
842 irqpoll [HW]
843 When an interrupt is not handled search all handlers
844 for it. Also check all handlers each timer
845 interrupt. Intended to get systems with badly broken
846 firmware running.
847
1da177e4 848 isapnp= [ISAPNP]
a9913044 849 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
850
851 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
852 Format:
853 <cpu number>,...,<cpu number>
854 or
855 <cpu number>-<cpu number> (must be a positive range in ascending order)
856 or a mixture
857 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
858 This option can be used to specify one or more CPUs
859 to isolate from the general SMP balancing and scheduling
860 algorithms. The only way to move a process onto or off
861 an "isolated" CPU is via the CPU affinity syscalls.
862 <cpu number> begins at 0 and the maximum value is
863 "number of CPUs in system - 1".
864
865 This option is the preferred way to isolate CPUs. The
a9913044
RD
866 alternative -- manually setting the CPU mask of all
867 tasks in the system -- can cause problems and
868 suboptimal load balancer performance.
1da177e4 869
a9913044 870 iucv= [HW,NET]
1da177e4
LT
871
872 js= [HW,JOY] Analog joystick
873 See Documentation/input/joystick.txt.
874
cd4f0ef7 875 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
876 specifies the amount of memory usable by the kernel
877 for non-movable allocations. The requested amount is
878 spread evenly throughout all nodes in the system. The
879 remaining memory in each node is used for Movable
880 pages. In the event, a node is too small to have both
881 kernelcore and Movable pages, kernelcore pages will
882 take priority and other nodes will have a larger number
883 of kernelcore pages. The Movable zone is used for the
884 allocation of pages that may be reclaimed or moved
885 by the page migration subsystem. This means that
886 HugeTLB pages may not be allocated from this zone.
887 Note that allocations like PTEs-from-HighMem still
888 use the HighMem zone if it exists, and the Normal
889 zone if it does not.
890
cd4f0ef7 891 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
892 is similar to kernelcore except it specifies the
893 amount of memory used for migratable allocations.
894 If both kernelcore and movablecore is specified,
895 then kernelcore will be at *least* the specified
896 value but may be more. If movablecore on its own
897 is specified, the administrator must be careful
898 that the amount of memory usable for all allocations
899 is not too small.
900
1da177e4
LT
901 keepinitrd [HW,ARM]
902
cd4f0ef7 903 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
904 in oops dumps.
905
906 l2cr= [PPC]
907
cd4f0ef7 908 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 909 disabled it.
1da177e4 910
cd4f0ef7 911 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
912 C2 power state.
913
fcb71f6f
FC
914 libata.dma= [LIBATA] DMA control
915 libata.dma=0 Disable all PATA and SATA DMA
916 libata.dma=1 PATA and SATA Disk DMA only
917 libata.dma=2 ATAPI (CDROM) DMA only
918 libata.dma=4 Compact Flash DMA only
919 Combinations also work, so libata.dma=3 enables DMA
920 for disks and CDROMs, but not CFs.
921
78e70c23
DJ
922 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
923 when set.
924 Format: <int>
925
1da177e4
LT
926 load_ramdisk= [RAM] List of ramdisks to load from floppy
927 See Documentation/ramdisk.txt.
928
a6b25b67
RD
929 lockd.nlm_grace_period=P [NFS] Assign grace period.
930 Format: <integer>
1da177e4 931
a6b25b67
RD
932 lockd.nlm_tcpport=N [NFS] Assign TCP port.
933 Format: <integer>
934
935 lockd.nlm_timeout=T [NFS] Assign timeout value.
936 Format: <integer>
937
938 lockd.nlm_udpport=M [NFS] Assign UDP port.
939 Format: <integer>
1da177e4
LT
940
941 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
942 Format: <irq>
943
944 loglevel= All Kernel Messages with a loglevel smaller than the
945 console loglevel will be printed to the console. It can
946 also be changed with klogd or other programs. The
947 loglevels are defined as follows:
948
949 0 (KERN_EMERG) system is unusable
950 1 (KERN_ALERT) action must be taken immediately
951 2 (KERN_CRIT) critical conditions
952 3 (KERN_ERR) error conditions
953 4 (KERN_WARNING) warning conditions
954 5 (KERN_NOTICE) normal but significant condition
955 6 (KERN_INFO) informational
956 7 (KERN_DEBUG) debug-level messages
957
958 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
959 Format: { n | nk | nM }
960 n must be a power of two. The default size
961 is set in the kernel config file.
1da177e4 962
accaa24c
RD
963 logo.nologo [FB] Disables display of the built-in Linux logo.
964 This may be used to provide more screen space for
965 kernel log messages and is useful when debugging
966 kernel boot problems.
967
1da177e4
LT
968 lp=0 [LP] Specify parallel ports to use, e.g,
969 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
970 lp=reset first parallel port). 'lp=0' disables the
971 lp=auto printer driver. 'lp=reset' (which can be
972 specified in addition to the ports) causes
973 attached printers to be reset. Using
974 lp=port1,port2,... specifies the parallel ports
975 to associate lp devices with, starting with
976 lp0. A port specification may be 'none' to skip
977 that lp device, or a parport name such as
978 'parport0'. Specifying 'lp=auto' instead of a
979 port specification list means that device IDs
980 from each port should be examined, to see if
981 an IEEE 1284-compliant printer is attached; if
982 so, the driver will manage that printer.
983 See also header of drivers/char/lp.c.
984
985 lpj=n [KNL]
986 Sets loops_per_jiffy to given constant, thus avoiding
987 time-consuming boot-time autodetection (up to 250 ms per
988 CPU). 0 enables autodetection (default). To determine
989 the correct value for your kernel, boot with normal
990 autodetection and see what value is printed. Note that
991 on SMP systems the preset will be applied to all CPUs,
992 which is likely to cause problems if your CPUs need
993 significantly divergent settings. An incorrect value
994 will cause delays in the kernel to be wrong, leading to
995 unpredictable I/O errors and other breakage. Although
996 unlikely, in the extreme case this might damage your
997 hardware.
998
999 ltpc= [NET]
1000 Format: <io>,<irq>,<dma>
1001
a9913044
RD
1002 mac5380= [HW,SCSI] Format:
1003 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1004
a9913044
RD
1005 mac53c9x= [HW,SCSI] Format:
1006 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1007
a9913044
RD
1008 machvec= [IA64] Force the use of a particular machine-vector
1009 (machvec) in a generic kernel.
1010 Example: machvec=hpzx1_swiotlb
1da177e4 1011
a9913044 1012 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1013 be mounted
1014 Format: <1-256>
1015
1016 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1017 should make use of. maxcpus=n : n >= 0 limits the
1018 kernel to using 'n' processors. n=0 is a special case,
1019 it is equivalent to "nosmp", which also disables
1020 the IO APIC.
1da177e4 1021
2b2c3750
BP
1022 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1023 equal to this physical address is ignored.
1024
a9913044 1025 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1026 Should be between 1 and 2^32-1.
1027
1028 max_report_luns=
a9913044 1029 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1030 Should be between 1 and 16384.
1031
cd4f0ef7 1032 mca-pentium [BUGS=X86-32]
1da177e4
LT
1033
1034 mcatest= [IA-64]
1035
cd4f0ef7 1036 mce [X86-32] Machine Check Exception
1da177e4 1037
909dd324
AK
1038 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1039
1da177e4
LT
1040 md= [HW] RAID subsystems devices and level
1041 See Documentation/md.txt.
a9913044 1042
1da177e4
LT
1043 mdacon= [MDA]
1044 Format: <first>,<last>
1045 Specifies range of consoles to be captured by the MDA.
a9913044 1046
1da177e4
LT
1047 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1048 Amount of memory to be used when the kernel is not able
1049 to see the whole system memory or for test.
cd4f0ef7 1050 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1051 address space collisions. Without memmap= PCI devices
1052 could be placed at addresses belonging to unused RAM.
1053
cd4f0ef7 1054 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1055 memory.
1056
cd4f0ef7 1057 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1058 E820 memory map, as specified by the user.
1059 Such memmap=exactmap lines can be constructed based on
1060 BIOS output or other requirements. See the memmap=nn@ss
1061 option description.
1062
1063 memmap=nn[KMG]@ss[KMG]
1064 [KNL] Force usage of a specific region of memory
1065 Region of memory to be used, from ss to ss+nn.
1066
1067 memmap=nn[KMG]#ss[KMG]
1068 [KNL,ACPI] Mark specific memory as ACPI data.
1069 Region of memory to be used, from ss to ss+nn.
1070
1071 memmap=nn[KMG]$ss[KMG]
1072 [KNL,ACPI] Mark specific memory as reserved.
1073 Region of memory to be used, from ss to ss+nn.
1074
1075 meye.*= [HW] Set MotionEye Camera parameters
1076 See Documentation/video4linux/meye.txt.
1077
8f36881b
AS
1078 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1079 Multi-Function General Purpose Timers on AMD Geode
1080 platforms.
1081
1da177e4
LT
1082 mga= [HW,DRM]
1083
1084 mousedev.tap_time=
1085 [MOUSE] Maximum time between finger touching and
1086 leaving touchpad surface for touch to be considered
1087 a tap and be reported as a left button click (for
1088 touchpads working in absolute mode only).
1089 Format: <msecs>
1090 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1091 reporting absolute coordinates, such as tablets
1092 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1093 reporting absolute coordinates, such as tablets
1094
1095 mpu401= [HW,OSS]
1096 Format: <io>,<irq>
1097
1098 MTD_Partition= [MTD]
1099 Format: <name>,<region-number>,<size>,<offset>
1100
a9913044
RD
1101 MTD_Region= [MTD] Format:
1102 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1103
1104 mtdparts= [MTD]
c8facbb6 1105 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1106
1107 mtouchusb.raw_coordinates=
a9913044
RD
1108 [HW] Make the MicroTouch USB driver use raw coordinates
1109 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1110
1111 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1112
1113 NCR_D700= [HW,SCSI]
1114 See header of drivers/scsi/NCR_D700.c.
1115
1116 ncr5380= [HW,SCSI]
1117
1118 ncr53c400= [HW,SCSI]
1119
1120 ncr53c400a= [HW,SCSI]
1121
1122 ncr53c406a= [HW,SCSI]
1123
1124 ncr53c8xx= [HW,SCSI]
1125
1126 netdev= [NET] Network devices parameters
1127 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1128 Note that mem_start is often overloaded to mean
1129 something different and driver-specific.
a9913044
RD
1130 This usage is only documented in each driver source
1131 file if at all.
1132
1da177e4
LT
1133 nfsaddrs= [NFS]
1134 See Documentation/nfsroot.txt.
1135
1136 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1137 See Documentation/nfsroot.txt.
1138
a72b4422
TM
1139 nfs.callback_tcpport=
1140 [NFS] set the TCP port on which the NFSv4 callback
1141 channel should listen.
1142
58df095b
TM
1143 nfs.idmap_cache_timeout=
1144 [NFS] set the maximum lifetime for idmapper cache
1145 entries.
1146
f43bf0be
TM
1147 nfs.enable_ino64=
1148 [NFS] enable 64-bit inode numbers.
1149 If zero, the NFS client will fake up a 32-bit inode
1150 number for the readdir() and stat() syscalls instead
1151 of returning the full 64-bit number.
1152 The default is to return 64-bit inode numbers.
1153
e7ba176b
HS
1154 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1155 when a NMI is triggered.
1156 Format: [state][,regs][,debounce][,die]
1157
cd4f0ef7 1158 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1159
cd4f0ef7 1160 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1161 emulation library even if a 387 maths coprocessor
1162 is present.
1163
c1aee215
CL
1164 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1165 caches in the slab allocator. Saves per-node memory,
1166 but will impact performance.
3395ee05 1167
a9913044
RD
1168 noalign [KNL,ARM]
1169
1da177e4
LT
1170 noapic [SMP,APIC] Tells the kernel to not make use of any
1171 IOAPICs that may be present in the system.
1172
1da177e4
LT
1173 nobats [PPC] Do not use BATs for mapping kernel lowmem
1174 on "Classic" PPC cores.
1175
1176 nocache [ARM]
a9913044 1177
163ecdff
SN
1178 nodelayacct [KNL] Disable per-task delay accounting
1179
1da177e4
LT
1180 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1181
8b2cb7a8
HY
1182 noefi [X86-32,X86-64] Disable EFI runtime services support.
1183
1da177e4
LT
1184 noexec [IA-64]
1185
cd4f0ef7 1186 noexec [X86-32,X86-64]
1da177e4
LT
1187 noexec=on: enable non-executable mappings (default)
1188 noexec=off: disable nn-executable mappings
1189
cd4f0ef7 1190 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1191 register save and restore. The kernel will only save
1192 legacy floating-point registers on task switch.
1da177e4 1193
191679fd
AK
1194 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1195
1da177e4 1196 nohlt [BUGS=ARM]
a9913044 1197
cd4f0ef7 1198 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1199 instruction doesn't work correctly and not to
1200 use it.
1201
1202 nohalt [IA-64] Tells the kernel not to use the power saving
1203 function PAL_HALT_LIGHT when idle. This increases
1204 power-consumption. On the positive side, it reduces
1205 interrupt wake-up latency, which may improve performance
1206 in certain environments such as networked servers or
1207 real-time systems.
1208
79bf2bb3
TG
1209 nohz= [KNL] Boottime enable/disable dynamic ticks
1210 Valid arguments: on, off
1211 Default: on
1212
cd4f0ef7 1213 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1214
cd4f0ef7 1215 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1216 disable unhandled interrupt sources.
1217
cd4f0ef7 1218 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1219 broken timer IRQ sources.
1220
1da177e4
LT
1221 noisapnp [ISAPNP] Disables ISA PnP code.
1222
1223 noinitrd [RAM] Tells the kernel not to load any configured
1224 initial RAM disk.
1225
1226 nointroute [IA-64]
1227
0aa366f3
TL
1228 nojitter [IA64] Disables jitter checking for ITC timers.
1229
cd4f0ef7 1230 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1231
cd4f0ef7 1232 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1233
1da177e4
LT
1234 noltlbs [PPC] Do not use large page/tlb entries for kernel
1235 lowmem mapping on PPC40x.
1236
312f1f01
H
1237 nomca [IA-64] Disable machine check abort handling
1238
cd4f0ef7 1239 nomce [X86-32] Machine Check Exception
abe37e5a 1240
83d7384f
AS
1241 nomfgpt [X86-32] Disable Multi-Function General Purpose
1242 Timer usage (for AMD Geode machines).
1243
cd4f0ef7 1244 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1245
cd4f0ef7 1246 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1247 with UP alternatives
1248
1da177e4
LT
1249 noresidual [PPC] Don't use residual data on PReP machines.
1250
a9913044
RD
1251 noresume [SWSUSP] Disables resume and restores original swap
1252 space.
1253
1da177e4
LT
1254 no-scroll [VGA] Disables scrollback.
1255 This is required for the Braillex ib80-piezo Braille
1256 reader made by F.H. Papenmeier (Germany).
1257
1258 nosbagart [IA-64]
1259
cd4f0ef7 1260 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1261
61ec7567
LB
1262 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1263 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1264
97842216
DJ
1265 nosoftlockup [KNL] Disable the soft-lockup detector.
1266
1da177e4
LT
1267 nosync [HW,M68K] Disables sync negotiation for all devices.
1268
cd4f0ef7 1269 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1270
1271 nousb [USB] Disable the USB subsystem
1272
1273 nowb [ARM]
a9913044 1274
f0c0b2b8
KH
1275 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1276 one of ['zone', 'node', 'default'] can be specified
1277 This can be set from sysctl after boot.
1278 See Documentation/sysctl/vm.txt for details.
1279
a61c2d78
DJ
1280 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1281
1da177e4
LT
1282 opl3= [HW,OSS]
1283 Format: <io>
1284
1da177e4
LT
1285 oprofile.timer= [HW]
1286 Use timer interrupt instead of performance counters
1287
1da177e4
LT
1288 osst= [HW,SCSI] SCSI Tape Driver
1289 Format: <buffer_size>,<write_threshold>
1290 See also Documentation/scsi/st.txt.
1291
1292 panic= [KNL] Kernel behaviour on panic
1293 Format: <timeout>
1294
1295 parkbd.port= [HW] Parallel port number the keyboard adapter is
1296 connected to, default is 0.
1297 Format: <parport#>
1298 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1299 0 for XT, 1 for AT (default is AT).
a9913044
RD
1300 Format: <mode>
1301
1302 parport= [HW,PPT] Specify parallel ports. 0 disables.
1303 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1304 Use 'auto' to force the driver to use any
1305 IRQ/DMA settings detected (the default is to
1306 ignore detected IRQ/DMA settings because of
1307 possible conflicts). You can specify the base
1308 address, IRQ, and DMA settings; IRQ and DMA
1309 should be numbers, or 'auto' (for using detected
1310 settings on that particular port), or 'nofifo'
1311 (to avoid using a FIFO even if it is detected).
1312 Parallel ports are assigned in the order they
1313 are specified on the command line, starting
1314 with parport0.
1315
1316 parport_init_mode= [HW,PPT]
1317 Configure VIA parallel port to operate in
1318 a specific mode. This is necessary on Pegasos
1319 computer where firmware has no options for setting
1320 up parallel port mode and sets it to spp.
1321 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1322 Format: [spp|ps2|epp|ecp|ecpepp]
1323
a9913044
RD
1324 pas2= [HW,OSS] Format:
1325 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1326
1da177e4
LT
1327 pas16= [HW,SCSI]
1328 See header of drivers/scsi/pas16.c.
1329
dd287796
AM
1330 pause_on_oops=
1331 Halt all CPUs after the first oops has been printed for
1332 the specified number of seconds. This is to be used if
1333 your oopses keep scrolling off the screen.
1334
1da177e4
LT
1335 pcbit= [HW,ISDN]
1336
1337 pcd. [PARIDE]
1338 See header of drivers/block/paride/pcd.c.
1339 See also Documentation/paride.txt.
1340
a9913044 1341 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1342 off [X86-32] don't probe for the PCI bus
1343 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1344 the hardware directly. Use this if your machine
1345 has a non-standard PCI host bridge.
cd4f0ef7 1346 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1347 hardware access methods are allowed. Use this
1348 if you experience crashes upon bootup and you
1349 suspect they are caused by the BIOS.
cd4f0ef7 1350 conf1 [X86-32] Force use of PCI Configuration
a9913044 1351 Mechanism 1.
cd4f0ef7 1352 conf2 [X86-32] Force use of PCI Configuration
a9913044 1353 Mechanism 2.
7f785763
RD
1354 noaer [PCIE] If the PCIEAER kernel config parameter is
1355 enabled, this kernel boot option can be used to
1356 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1357 nodomains [PCI] Disable support for multiple PCI
1358 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1359 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1360 Configuration
309e57df
MW
1361 nomsi [MSI] If the PCI_MSI kernel config parameter is
1362 enabled, this kernel boot option can be used to
1363 disable the use of MSI interrupts system-wide.
cd4f0ef7 1364 nosort [X86-32] Don't sort PCI devices according to
a9913044
RD
1365 order given by the PCI BIOS. This sorting is
1366 done to get a device order compatible with
1367 older kernels.
cd4f0ef7 1368 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1369 routing table. These calls are known to be buggy
1370 on several machines and they hang the machine
1371 when used, but on other computers it's the only
1372 way to get the interrupt routing table. Try
1373 this option if the kernel is unable to allocate
1374 IRQs or discover secondary PCI buses on your
1375 motherboard.
cd4f0ef7 1376 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1377 Use with caution as certain devices share
1378 address decoders between ROMs and other
1379 resources.
cd4f0ef7 1380 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1381 assigned automatically to PCI devices. You can
1382 make the kernel exclude IRQs of your ISA cards
1383 this way.
cd4f0ef7 1384 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1385 of the PIRQ table (normally generated
1386 by the BIOS) if it is outside the
1387 F0000h-100000h range.
cd4f0ef7 1388 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1389 useful if the kernel is unable to find your
1390 secondary buses and you want to tell it
1391 explicitly which ones they are.
cd4f0ef7 1392 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1393 numbers ourselves, overriding
1394 whatever the firmware may have done.
cd4f0ef7 1395 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1396 in the BIOS $PIR table. This is needed on
1397 some systems with broken BIOSes, notably
1398 some HP Pavilion N5400 and Omnibook XE3
1399 notebooks. This will have no effect if ACPI
1400 IRQ routing is enabled.
cd4f0ef7 1401 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1402 or for PCI scanning.
62f420f8
GH
1403 use_crs [X86-32] Use _CRS for PCI resource
1404 allocation.
a9913044
RD
1405 routeirq Do IRQ routing for all PCI devices.
1406 This is normally done in pci_enable_device(),
1407 so this option is a temporary workaround
1408 for broken drivers that don't call it.
1409 firmware [ARM] Do not re-enumerate the bus but instead
1410 just use the configuration from the
1411 bootloader. This is currently used on
1412 IXP2000 systems where the bus has to be
1413 configured a certain way for adjunct CPUs.
0637a70a
AK
1414 noearly [X86] Don't do any early type 1 scanning.
1415 This might help on some broken boards which
1416 machine check when some devices' config space
1417 is read. But various workarounds are disabled
1418 and some IOMMU drivers will not work.
6b4b78fe
MD
1419 bfsort Sort PCI devices into breadth-first order.
1420 This sorting is done to get a device
1421 order compatible with older (<= 2.4) kernels.
1422 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1423 cbiosize=nn[KMG] The fixed amount of bus space which is
1424 reserved for the CardBus bridge's IO window.
1425 The default value is 256 bytes.
1426 cbmemsize=nn[KMG] The fixed amount of bus space which is
1427 reserved for the CardBus bridge's memory
1428 window. The default value is 64 megabytes.
6b4b78fe 1429
1da177e4
LT
1430 pcmv= [HW,PCMCIA] BadgePAD 4
1431
1432 pd. [PARIDE]
1433 See Documentation/paride.txt.
1434
1435 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1436 boot time.
1437 Format: { 0 | 1 }
1438 See arch/parisc/kernel/pdc_chassis.c
1439
1440 pf. [PARIDE]
1441 See Documentation/paride.txt.
1442
1443 pg. [PARIDE]
1444 See Documentation/paride.txt.
1445
1446 pirq= [SMP,APIC] Manual mp-table setup
1447 See Documentation/i386/IO-APIC.txt.
1448
1449 plip= [PPT,NET] Parallel port network link
1450 Format: { parport<nr> | timid | 0 }
1451 See also Documentation/parport.txt.
1452
1453 pnpacpi= [ACPI]
1454 { off }
1455
1456 pnpbios= [ISAPNP]
1457 { on | off | curr | res | no-curr | no-res }
1458
1459 pnp_reserve_irq=
1460 [ISAPNP] Exclude IRQs for the autoconfiguration
1461
1462 pnp_reserve_dma=
1463 [ISAPNP] Exclude DMAs for the autoconfiguration
1464
1465 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1466 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1467
1468 pnp_reserve_mem=
a9913044
RD
1469 [ISAPNP] Exclude memory regions for the
1470 autoconfiguration.
1da177e4
LT
1471 Ranges are in pairs (memory base and size).
1472
45807a1d
IM
1473 print-fatal-signals=
1474 [KNL] debug: print fatal signals
1475 print-fatal-signals=1: print segfault info to
1476 the kernel console.
1477 default: off.
1478
e84845c4
RD
1479 printk.time= Show timing data prefixed to each printk message line
1480 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1481
1da177e4 1482 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1483 Format: [schedule,]<number>
1484 Param: "schedule" - profile schedule points.
1485 Param: <number> - step/bucket size as a power of 2 for
1486 statistical time based profiling.
b3da2a73
MG
1487 Param: "sleep" - profile D-state sleeping (millisecs).
1488 Requires CONFIG_SCHEDSTATS
c0fe2e69 1489 Param: "kvm" - profile VM exits.
1da177e4 1490
a9913044 1491 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1492 Limit processor to maximum C-state
1493 max_cstate=9 overrides any DMI blacklist limit.
1494
41c0d868
LB
1495 processor.nocst [HW,ACPI]
1496 Ignore the _CST method to determine C-states,
1497 instead using the legacy FADT method
1498
1da177e4
LT
1499 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1500 before loading.
1501 See Documentation/ramdisk.txt.
1502
a9913044
RD
1503 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1504 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1505 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1506 per second.
a9913044
RD
1507 psmouse.resetafter= [HW,MOUSE]
1508 Try to reset the device after so many bad packets
1da177e4
LT
1509 (0 = never).
1510 psmouse.resolution=
1511 [HW,MOUSE] Set desired mouse resolution, in dpi.
1512 psmouse.smartscroll=
a9913044 1513 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1514 0 = disabled, 1 = enabled (default).
1515
1516 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1517 Format:
1518 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1519
1520 pt. [PARIDE]
1521 See Documentation/paride.txt.
1522
dc8c8587
KS
1523 pty.legacy_count=
1524 [KNL] Number of legacy pty's. Overwrites compiled-in
1525 default number.
1526
7d2c502f 1527 quiet [KNL] Disable most log messages
a9913044 1528
1da177e4
LT
1529 r128= [HW,DRM]
1530
1531 raid= [HW,RAID]
1532 See Documentation/md.txt.
1533
a9913044 1534 ramdisk_blocksize= [RAM]
1da177e4 1535 See Documentation/ramdisk.txt.
a9913044 1536
1da177e4 1537 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1538 See Documentation/ramdisk.txt.
1539
21a1ea9e
DS
1540 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1541 RCU callbacks to process in one batch.
1542
1543 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1544 RCU callbacks over which batch limiting is disabled.
1545
1546 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1547 RCU callbacks below which batch limiting is re-enabled.
1548
ffdfc409
OJ
1549 rdinit= [KNL]
1550 Format: <full_path>
1551 Run specified binary instead of /init from the ramdisk,
1552 used for early userspace startup. See initrd.
1553
cd4f0ef7 1554 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1555 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1556 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1557
1558 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1559
cd4f0ef7 1560 reservetop= [X86-32]
461a9aff
ZA
1561 Format: nn[KMG]
1562 Reserves a hole at the top of the kernel virtual
1563 address space.
1564
7e96287d
VG
1565 reset_devices [KNL] Force drivers to reset the underlying device
1566 during initialization.
1567
a9913044
RD
1568 resume= [SWSUSP]
1569 Specify the partition device for software suspend
1da177e4 1570
ecbd0da1
RW
1571 resume_offset= [SWSUSP]
1572 Specify the offset from the beginning of the partition
1573 given by "resume=" at which the swap header is located,
1574 in <PAGE_SIZE> units (needed only for swap files).
1575 See Documentation/power/swsusp-and-swap-files.txt
1576
0a7b35cb
MN
1577 retain_initrd [RAM] Keep initrd memory after extraction
1578
1da177e4
LT
1579 rhash_entries= [KNL,NET]
1580 Set number of hash buckets for route cache
1581
1582 riscom8= [HW,SERIAL]
1583 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1584
1585 ro [KNL] Mount root device read-only on boot
1586
1587 root= [KNL] Root filesystem
1588
1589 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1590 mount the root filesystem
1591
1592 rootflags= [KNL] Set root filesystem mount option string
1593
1594 rootfstype= [KNL] Set root filesystem type
1595
cc1ed754
PO
1596 rootwait [KNL] Wait (indefinitely) for root device to show up.
1597 Useful for devices that are detected asynchronously
1598 (e.g. USB and MMC devices).
1599
20510f2f
JM
1600 root_plug.vendor_id=
1601 [ROOTPLUG] Override the default vendor ID
1602
1603 root_plug.product_id=
1604 [ROOTPLUG] Override the default product ID
1605
1606 root_plug.debug=
1607 [ROOTPLUG] Enable debugging output
1608
1da177e4
LT
1609 rw [KNL] Mount root device read-write on boot
1610
1611 S [KNL] Run init in single mode
1612
1613 sa1100ir [NET]
1614 See drivers/net/irda/sa1100_ir.c.
1615
1da177e4 1616 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1617
1da177e4
LT
1618 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1619 Format: <io>[,<timeout>[,<isapnp>]]
1620
1621 scsi_debug_*= [SCSI]
1622 See drivers/scsi/scsi_debug.c.
1623
1624 scsi_default_dev_flags=
1625 [SCSI] SCSI default device flags
1626 Format: <integer>
1627
1628 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1629 Format: <vendor>:<model>:<flags>
1630 (flags are integer value)
1631
6af6632a
RD
1632 scsi_logging_level= [SCSI] a bit mask of logging levels
1633 See drivers/scsi/scsi_logging.h for bits. Also
1634 settable via sysctl at dev.scsi.logging_level
1635 (/proc/sys/dev/scsi/logging_level).
1636 There is also a nice 'scsi_logging_level' script in the
1637 S390-tools package, available for download at
1638 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1639
3e082a91
MW
1640 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1641 discovered. async scans them in kernel threads,
1642 allowing boot to proceed. none ignores them, expecting
1643 user space to do the scan.
1644
1da177e4
LT
1645 selinux [SELINUX] Disable or enable SELinux at boot time.
1646 Format: { "0" | "1" }
1647 See security/selinux/Kconfig help text.
1648 0 -- disable.
1649 1 -- enable.
1650 Default value is set via kernel config option.
1651 If enabled at boot time, /selinux/disable can be used
1652 later to disable prior to initial policy load.
1653
4e5ab4cb
JM
1654 selinux_compat_net =
1655 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1656 Format: { "0" | "1" }
1657 0 -- use new secmark-based packet controls
1658 1 -- use legacy packet controls
1659 Default value is 0 (preferred).
1660 Value can be changed at runtime via
1661 /selinux/compat_net.
4e5ab4cb 1662
cd4f0ef7 1663 serialnumber [BUGS=X86-32]
1da177e4 1664
1da177e4
LT
1665 shapers= [NET]
1666 Maximal number of shapers.
a9913044 1667
1da177e4
LT
1668 sim710= [SCSI,HW]
1669 See header of drivers/scsi/sim710.c.
1670
1671 simeth= [IA-64]
1672 simscsi=
a9913044 1673
1da177e4
LT
1674 slram= [HW,MTD]
1675
f0630fff
CL
1676 slub_debug[=options[,slabs]] [MM, SLUB]
1677 Enabling slub_debug allows one to determine the
1678 culprit if slab objects become corrupted. Enabling
1679 slub_debug can create guard zones around objects and
1680 may poison objects when not in use. Also tracks the
1681 last alloc / free. For more information see
1682 Documentation/vm/slub.txt.
c1aee215
CL
1683
1684 slub_max_order= [MM, SLUB]
f0630fff
CL
1685 Determines the maximum allowed order for slabs.
1686 A high setting may cause OOMs due to memory
1687 fragmentation. For more information see
1688 Documentation/vm/slub.txt.
c1aee215
CL
1689
1690 slub_min_objects= [MM, SLUB]
f0630fff
CL
1691 The minimum number of objects per slab. SLUB will
1692 increase the slab order up to slub_max_order to
1693 generate a sufficiently large slab able to contain
1694 the number of objects indicated. The higher the number
1695 of objects the smaller the overhead of tracking slabs
1696 and the less frequently locks need to be acquired.
c1aee215
CL
1697 For more information see Documentation/vm/slub.txt.
1698
1699 slub_min_order= [MM, SLUB]
1700 Determines the mininum page order for slabs. Must be
f0630fff 1701 lower than slub_max_order.
c1aee215
CL
1702 For more information see Documentation/vm/slub.txt.
1703
1704 slub_nomerge [MM, SLUB]
f0630fff 1705 Disable merging of slabs with similar size. May be
c1aee215 1706 necessary if there is some reason to distinguish
f0630fff
CL
1707 allocs to different slabs. Debug options disable
1708 merging on their own.
c1aee215
CL
1709 For more information see Documentation/vm/slub.txt.
1710
1da177e4
LT
1711 smart2= [HW]
1712 Format: <io1>[,<io2>[,...,<io8>]]
1713
cd4f0ef7 1714 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1715 attempt to substitute SMP alternatives once at boot.
1716
d0d4f69b
BH
1717 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1718 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1719 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1720 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1721 smsc-ircc2.ircc_irq= [HW] IRQ line
1722 smsc-ircc2.ircc_dma= [HW] DMA channel
1723 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1724 0: Toshiba Satellite 1800 (GP data pin select)
1725 1: Fast pin select (default)
1726 2: ATC IRMode
1727
1da177e4
LT
1728 snd-ad1816a= [HW,ALSA]
1729
1730 snd-ad1848= [HW,ALSA]
1731
1732 snd-ali5451= [HW,ALSA]
1733
1734 snd-als100= [HW,ALSA]
1735
1736 snd-als4000= [HW,ALSA]
1737
1738 snd-azt2320= [HW,ALSA]
1739
1740 snd-cmi8330= [HW,ALSA]
1741
1742 snd-cmipci= [HW,ALSA]
1743
1744 snd-cs4231= [HW,ALSA]
1745
1746 snd-cs4232= [HW,ALSA]
1747
1748 snd-cs4236= [HW,ALSA]
1749
1750 snd-cs4281= [HW,ALSA]
1751
1752 snd-cs46xx= [HW,ALSA]
1753
1754 snd-dt019x= [HW,ALSA]
1755
1756 snd-dummy= [HW,ALSA]
1757
1758 snd-emu10k1= [HW,ALSA]
1759
1760 snd-ens1370= [HW,ALSA]
1761
1762 snd-ens1371= [HW,ALSA]
1763
1764 snd-es968= [HW,ALSA]
1765
1766 snd-es1688= [HW,ALSA]
1767
1768 snd-es18xx= [HW,ALSA]
1769
1770 snd-es1938= [HW,ALSA]
1771
1772 snd-es1968= [HW,ALSA]
1773
1774 snd-fm801= [HW,ALSA]
1775
1776 snd-gusclassic= [HW,ALSA]
1777
1778 snd-gusextreme= [HW,ALSA]
1779
1780 snd-gusmax= [HW,ALSA]
1781
1782 snd-hdsp= [HW,ALSA]
1783
1784 snd-ice1712= [HW,ALSA]
1785
1786 snd-intel8x0= [HW,ALSA]
1787
1788 snd-interwave= [HW,ALSA]
1789
1790 snd-interwave-stb=
1791 [HW,ALSA]
1792
1793 snd-korg1212= [HW,ALSA]
1794
1795 snd-maestro3= [HW,ALSA]
1796
1797 snd-mpu401= [HW,ALSA]
1798
1799 snd-mtpav= [HW,ALSA]
1800
1801 snd-nm256= [HW,ALSA]
1802
1803 snd-opl3sa2= [HW,ALSA]
1804
1805 snd-opti92x-ad1848=
1806 [HW,ALSA]
1807
1808 snd-opti92x-cs4231=
1809 [HW,ALSA]
1810
1811 snd-opti93x= [HW,ALSA]
1812
1813 snd-pmac= [HW,ALSA]
1814
1815 snd-rme32= [HW,ALSA]
1816
1817 snd-rme96= [HW,ALSA]
1818
1819 snd-rme9652= [HW,ALSA]
1820
1821 snd-sb8= [HW,ALSA]
1822
1823 snd-sb16= [HW,ALSA]
1824
1825 snd-sbawe= [HW,ALSA]
1826
1827 snd-serial= [HW,ALSA]
1828
1829 snd-sgalaxy= [HW,ALSA]
1830
1831 snd-sonicvibes= [HW,ALSA]
1832
1833 snd-sun-amd7930=
1834 [HW,ALSA]
1835
1836 snd-sun-cs4231= [HW,ALSA]
1837
1838 snd-trident= [HW,ALSA]
1839
1840 snd-usb-audio= [HW,ALSA,USB]
1841
1842 snd-via82xx= [HW,ALSA]
1843
1844 snd-virmidi= [HW,ALSA]
1845
1846 snd-wavefront= [HW,ALSA]
1847
1848 snd-ymfpci= [HW,ALSA]
a9913044 1849
1da177e4
LT
1850 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1851 See Documentation/sonypi.txt
1852
1853 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1854 See Documentation/specialix.txt.
1855
1856 spia_io_base= [HW,MTD]
1857 spia_fio_base=
1858 spia_pedr=
1859 spia_peddr=
1860
1861 sscape= [HW,OSS]
1862 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1863
1da177e4
LT
1864 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1865 See Documentation/scsi/st.txt.
1866
1867 st0x= [HW,SCSI]
1868 See header of drivers/scsi/seagate.c.
1869
1870 sti= [PARISC,HW]
1871 Format: <num>
1872 Set the STI (builtin display/keyboard on the HP-PARISC
1873 machines) console (graphic card) which should be used
1874 as the initial boot-console.
1875 See also comment in drivers/video/console/sticore.c.
1876
1877 sti_font= [HW]
1878 See comment in drivers/video/console/sticore.c.
1879
1880 stifb= [HW]
1881 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1882
42a7fc4a
GB
1883 sunrpc.pool_mode=
1884 [NFS]
1885 Control how the NFS server code allocates CPUs to
1886 service thread pools. Depending on how many NICs
1887 you have and where their interrupts are bound, this
1888 option will affect which CPUs will do NFS serving.
1889 Note: this parameter cannot be changed while the
1890 NFS server is running.
1891
1892 auto the server chooses an appropriate mode
1893 automatically using heuristics
1894 global a single global pool contains all CPUs
1895 percpu one pool for each CPU
1896 pernode one pool for each NUMA node (equivalent
1897 to global on non-NUMA machines)
1898
1da177e4 1899 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1900
1da177e4
LT
1901 switches= [HW,M68k]
1902
1903 sym53c416= [HW,SCSI]
1904 See header of drivers/scsi/sym53c416.c.
1905
5d6f647f
IM
1906 sysrq_always_enabled
1907 [KNL]
1908 Ignore sysrq setting - this boot parameter will
1909 neutralize any effect of /proc/sys/kernel/sysrq.
1910 Useful for debugging.
1911
1da177e4
LT
1912 t128= [HW,SCSI]
1913 See header of drivers/scsi/t128.c.
1914
1915 tdfx= [HW,DRM]
1916
1917 thash_entries= [KNL,NET]
1918 Set number of hash buckets for TCP connection
1919
f8707ec9
LB
1920 thermal.act= [HW,ACPI]
1921 -1: disable all active trip points in all thermal zones
1922 <degrees C>: override all lowest active trip points
1923
c52a7419
LB
1924 thermal.crt= [HW,ACPI]
1925 -1: disable all critical trip points in all thermal zones
1926 <degrees C>: lower all critical trip points
1927
f5487145
LB
1928 thermal.nocrt= [HW,ACPI]
1929 Set to disable actions on ACPI thermal zone
1930 critical and hot trip points.
1931
72b33ef8
LB
1932 thermal.off= [HW,ACPI]
1933 1: disable ACPI thermal control
1934
a70cdc52
LB
1935 thermal.psv= [HW,ACPI]
1936 -1: disable all passive trip points
1937 <degrees C>: override all passive trip points to this value
1938
730ff34d
LB
1939 thermal.tzp= [HW,ACPI]
1940 Specify global default ACPI thermal zone polling rate
1941 <deci-seconds>: poll all this frequency
1942 0: no polling (default)
1943
1da177e4 1944 time Show timing data prefixed to each printk message line
e84845c4 1945 [deprecated, see 'printk.time']
1da177e4
LT
1946
1947 tipar.timeout= [HW,PPT]
1948 Set communications timeout in tenths of a second
1949 (default 15).
1950
1951 tipar.delay= [HW,PPT]
1952 Set inter-bit delay in microseconds (default 10).
1953
1954 tmc8xx= [HW,SCSI]
1955 See header of drivers/scsi/seagate.c.
1956
1957 tmscsim= [HW,SCSI]
1958 See comment before function dc390_setup() in
1959 drivers/scsi/tmscsim.c.
1960
1961 tp720= [HW,PS2]
1962
1963 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
1964 Format:
1965 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1966
a9913044
RD
1967 turbografx.map[2|3]= [HW,JOY]
1968 TurboGraFX parallel port interface
1969 Format:
1970 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
1971 See also Documentation/input/joystick-parport.txt
1972
1973 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1974 See header of drivers/scsi/u14-34f.c.
1975
1976 uart401= [HW,OSS]
1977 Format: <io>,<irq>
1978
1979 uart6850= [HW,OSS]
1980 Format: <io>,<irq>
1981
5f8364b7
AS
1982 uhci-hcd.ignore_oc=
1983 [USB] Ignore overcurrent events (default N).
1984 Some badly-designed motherboards generate lots of
1985 bogus events, for ports that aren't wired to
1986 anything. Set this parameter to avoid log spamming.
1987 Note that genuine overcurrent events won't be
1988 reported either.
1989
b5e795f8
AS
1990 usbcore.autosuspend=
1991 [USB] The autosuspend time delay (in seconds) used
1992 for newly-detected USB devices (default 2). This
1993 is the time required before an idle device will be
1994 autosuspended. Devices for which the delay is set
eaafbc3a 1995 to a negative value won't be autosuspended at all.
b5e795f8 1996
1da177e4
LT
1997 usbhid.mousepoll=
1998 [USBHID] The interval which mice are to be polled at.
a9913044 1999
cd4f0ef7 2000 vdso= [X86-32,SH,x86-64]
1dbf527c 2001 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2002 vdso=1: enable VDSO (default)
2003 vdso=0: disable VDSO mapping
2004
af65d648
RM
2005 vdso32= [X86-32,X86-64]
2006 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2007 vdso32=1: enable 32-bit VDSO (default)
2008 vdso32=0: disable 32-bit VDSO mapping
2009
d080d397
YI
2010 vector= [IA-64,SMP]
2011 vector=percpu: enable percpu vector domain
2012
1da177e4
LT
2013 video= [FB] Frame buffer configuration
2014 See Documentation/fb/modedb.txt.
2015
cd4f0ef7 2016 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2017 See Documentation/i386/boot.txt and
2018 Documentation/svga.txt.
1da177e4
LT
2019 Use vga=ask for menu.
2020 This is actually a boot loader parameter; the value is
2021 passed to the kernel using a special protocol.
2022
a9913044 2023 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2024 size of <nn>. This can be used to increase the
2025 minimum size (128MB on x86). It can also be used to
2026 decrease the size and leave more room for directly
2027 mapped kernel RAM.
2028
585c3047
PO
2029 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2030 Format: <command>
1da177e4 2031
585c3047
PO
2032 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2033 Format: <command>
2034
2035 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2036 Format: <command>
a9913044 2037
1da177e4
LT
2038 waveartist= [HW,OSS]
2039 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2040
1da177e4
LT
2041 wd33c93= [HW,SCSI]
2042 See header of drivers/scsi/wd33c93.c.
2043
2044 wd7000= [HW,SCSI]
2045 See header of drivers/scsi/wd7000.c.
2046
2047 wdt= [WDT] Watchdog
8dfe9c21 2048 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2049
2050 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2051 xd_geo= See header of drivers/block/xd.c.
2052
2053 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2054 Format:
2055 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2056
a62eaf15
AK
2057 norandmaps Don't use address space randomization
2058 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2059
a9913044 2060______________________________________________________________________
1da177e4
LT
2061
2062TODO:
2063
2064 Add documentation for ALSA options.
2065 Add more DRM drivers.