x86, AMD IOMMU: add documentation for kernel parameters

[deliverable/linux.git] / Documentation / kernel-parameters.txt

                          Kernel Parameters
                          ~~~~~~~~~~~~~~~~~

The following is a consolidated list of the kernel parameters as implemented
(mostly) by the __setup() macro and sorted into English Dictionary order
(defined as ignoring all punctuation and sorting digits before letters in a
case insensitive manner), and with descriptions where known.

Module parameters for loadable modules are specified only as the
parameter name with optional '=' and value as appropriate, such as:

        modprobe usbcore blinkenlights=1

Module parameters for modules that are built into the kernel image
are specified on the kernel command line with the module name plus
'.' plus parameter name, with '=' and value if appropriate, such as:

        usbcore.blinkenlights=1

This document may not be entirely up to date and comprehensive. The command
"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
module. Loadable modules, after being loaded into the running kernel, also
reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
parameters may be changed at runtime by the command
"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".

The parameters listed below are only valid if certain kernel build options were
enabled and if respective hardware is present. The text in square brackets at
the beginning of each description states the restrictions within which a
parameter is applicable:

        ACPI    ACPI support is enabled.
        AGP     AGP (Accelerated Graphics Port) is enabled.
        ALSA    ALSA sound support is enabled.
        APIC    APIC support is enabled.
        APM     Advanced Power Management support is enabled.
        AVR32   AVR32 architecture is enabled.
        AX25    Appropriate AX.25 support is enabled.
        BLACKFIN Blackfin architecture is enabled.
        DRM     Direct Rendering Management support is enabled.
        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
        EFI     EFI Partitioning (GPT) is enabled
        EIDE    EIDE/ATAPI support is enabled.
        FB      The frame buffer device is enabled.
        HW      Appropriate hardware is enabled.
        IA-64   IA-64 architecture is enabled.
        IOSCHED More than one I/O scheduler is enabled.
        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
        ISAPNP  ISA PnP code is enabled.
        ISDN    Appropriate ISDN support is enabled.
        JOY     Appropriate joystick support is enabled.
        LIBATA  Libata driver is enabled
        LP      Printer support is enabled.
        LOOP    Loopback device support is enabled.
        M68k    M68k architecture is enabled.
                        These options have more detailed description inside of
                        Documentation/m68k/kernel-options.txt.
        MCA     MCA bus support is enabled.
        MDA     MDA console support is enabled.
        MOUSE   Appropriate mouse support is enabled.
        MSI     Message Signaled Interrupts (PCI).
        MTD     MTD (Memory Technology Device) support is enabled.
        NET     Appropriate network support is enabled.
        NUMA    NUMA support is enabled.
        GENERIC_TIME The generic timeofday code is enabled.
        NFS     Appropriate NFS support is enabled.
        OSS     OSS sound support is enabled.
        PV_OPS  A paravirtualized kernel is enabled.
        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
        PARISC  The PA-RISC architecture is enabled.
        PCI     PCI bus support is enabled.
        PCIE    PCI Express support is enabled.
        PCMCIA  The PCMCIA subsystem is enabled.
        PNP     Plug & Play support is enabled.
        PPC     PowerPC architecture is enabled.
        PPT     Parallel port support is enabled.
        PS2     Appropriate PS/2 support is enabled.
        RAM     RAM disk support is enabled.
        ROOTPLUG The example Root Plug LSM is enabled.
        S390    S390 architecture is enabled.
        SCSI    Appropriate SCSI support is enabled.
                        A lot of drivers has their options described inside of
                        Documentation/scsi/.
        SECURITY Different security models are enabled.
        SELINUX SELinux support is enabled.
        SERIAL  Serial support is enabled.
        SH      SuperH architecture is enabled.
        SMP     The kernel is an SMP kernel.
        SPARC   Sparc architecture is enabled.
        SWSUSP  Software suspend is enabled.
        TS      Appropriate touchscreen support is enabled.
        USB     USB support is enabled.
        USBHID  USB Human Interface Device support is enabled.
        V4L     Video For Linux support is enabled.
        VGA     The VGA console has been enabled.
        VT      Virtual terminal support is enabled.
        WDT     Watchdog support is enabled.
        XT      IBM PC/XT MFM hard disk support is enabled.
        X86-32  X86-32, aka i386 architecture is enabled.
        X86-64  X86-64 architecture is enabled.
                        More X86-64 boot options can be found in
                        Documentation/x86_64/boot-options.txt .

In addition, the following text indicates that the option:

        BUGS=   Relates to possible processor bugs on the said processor.
        KNL     Is a kernel start-up parameter.
        BOOT    Is a boot loader parameter.

Parameters denoted with BOOT are actually interpreted by the boot
loader, and have no meaning to the kernel directly.
Do not modify the syntax of boot loader parameters without extreme
need or coordination with <Documentation/i386/boot.txt>.

There are also arch-specific kernel-parameters not documented here.
See for example <Documentation/x86_64/boot-options.txt>.

Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
a trailing = on the name of any parameter states that that parameter will
be entered as an environment variable, whereas its absence indicates that
it will appear as a kernel argument readable via /proc/cmdline by programs
running once the system is up.

The number of kernel parameters is not limited, but the length of the
complete command line (parameters including spaces etc.) is limited to
a fixed number of characters. This limit depends on the architecture
and is between 256 and 4096 characters. It is defined in the file
./include/asm/setup.h as COMMAND_LINE_SIZE.


        acpi=           [HW,ACPI,X86-64,i386]
                        Advanced Configuration and Power Interface
                        Format: { force | off | ht | strict | noirq }
                        force -- enable ACPI if default was off
                        off -- disable ACPI if default was on
                        noirq -- do not use ACPI for IRQ routing
                        ht -- run only enough ACPI to enable Hyper Threading
                        strict -- Be less tolerant of platforms that are not
                                strictly ACPI specification compliant.

                        See also Documentation/power/pm.txt, pci=noacpi

        acpi_apic_instance=     [ACPI, IOAPIC]
                        Format: <int>
                        2: use 2nd APIC table, if available
                        1,0: use 1st APIC table
                        default: 0

        acpi_sleep=     [HW,ACPI] Sleep options
                        Format: { s3_bios, s3_mode, s3_beep }
                        See Documentation/power/video.txt for s3_bios and s3_mode.
                        s3_beep is for debugging; it makes the PC's speaker beep
                        as soon as the kernel's real-mode entry point is called.

        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
                        Format: { level | edge | high | low }

        acpi_irq_balance [HW,ACPI]
                        ACPI will balance active IRQs
                        default in APIC mode

        acpi_irq_nobalance [HW,ACPI]
                        ACPI will not move active IRQs (default)
                        default in PIC mode

        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
                        use by PCI
                        Format: <irq>,<irq>...

        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
                        Format: <irq>,<irq>...

        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT

        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
                        Format: To spoof as Windows 98: ="Microsoft Windows"

        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
                        acpi_osi="string1"      # add string1 -- only one string
                        acpi_osi="!string2"     # remove built-in string2
                        acpi_osi=               # disable all strings

        acpi_serialize  [HW,ACPI] force serialization of AML methods

        acpi_skip_timer_override [HW,ACPI]
                        Recognize and ignore IRQ0/pin2 Interrupt Override.
                        For broken nForce2 BIOS resulting in XT-PIC timer.
        acpi_use_timer_override [HW,ACPI}
                        Use timer override. For some broken Nvidia NF5 boards
                        that require a timer override, but don't have
                        HPET

        acpi.debug_layer=       [HW,ACPI]
                        Format: <int>
                        Each bit of the <int> indicates an ACPI debug layer,
                        1: enable, 0: disable. It is useful for boot time
                        debugging. After system has booted up, it can be set
                        via /sys/module/acpi/parameters/debug_layer.
                        CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
                        Available bits (add the numbers together) to enable debug output
                        for specific parts of the ACPI subsystem:
                        0x01 utilities 0x02 hardware 0x04 events 0x08 tables
                        0x10 namespace 0x20 parser 0x40 dispatcher
                        0x80 executer 0x100 resources 0x200 acpica debugger
                        0x400 os services 0x800 acpica disassembler.
                        The number can be in decimal or prefixed with 0x in hex.
                        Warning: Many of these options can produce a lot of
                        output and make your system unusable. Be very careful.

        acpi.debug_level=       [HW,ACPI]
                        Format: <int>
                        Each bit of the <int> indicates an ACPI debug level,
                        1: enable, 0: disable. It is useful for boot time
                        debugging. After system has booted up, it can be set
                        via /sys/module/acpi/parameters/debug_level.
                        CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
                        Available bits (add the numbers together) to enable different
                        debug output levels of the ACPI subsystem:
                        0x01 error 0x02 warn 0x04 init 0x08 debug object
                        0x10 info 0x20 init names 0x40 parse 0x80 load
                        0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
                        0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
                        0x10000 resources 0x20000 user requests 0x40000 package.
                        The number can be in decimal or prefixed with 0x in hex.
                        Warning: Many of these options can produce a lot of
                        output and make your system unusable. Be very careful.

        acpi_pm_good    [X86-32,X86-64]
                        Override the pmtimer bug detection: force the kernel
                        to assume that this machine's pmtimer latches its value
                        and always returns good values.

        agp=            [AGP]
                        { off | try_unsupported }
                        off: disable AGP support
                        try_unsupported: try to drive unsupported chipsets
                                (may crash computer or cause data corruption)

        enable_timer_pin_1 [i386,x86-64]
                        Enable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs
                        (in particular on some ATI chipsets).
                        The kernel tries to set a reasonable default.

        disable_timer_pin_1 [i386,x86-64]
                        Disable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs.

        ad1848=         [HW,OSS]
                        Format: <io>,<irq>,<dma>,<dma2>,<type>

        advansys=       [HW,SCSI]
                        See header of drivers/scsi/advansys.c.

        advwdt=         [HW,WDT] Advantech WDT
                        Format: <iostart>,<iostop>

        aedsp16=        [HW,OSS] Audio Excel DSP 16
                        Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
                        See also header of sound/oss/aedsp16.c.

        aha152x=        [HW,SCSI]
                        See Documentation/scsi/aha152x.txt.

        aha1542=        [HW,SCSI]
                        Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]

        aic7xxx=        [HW,SCSI]
                        See Documentation/scsi/aic7xxx.txt.

        aic79xx=        [HW,SCSI]
                        See Documentation/scsi/aic79xx.txt.

        amd_iommu=      [HW,X86-84]
                        Pass parameters to the AMD IOMMU driver in the system.
                        Possible values are:
                        off     - disable the driver for AMD IOMMU
                        isolate - enable device isolation (each device, as far
                                  as possible, will get its own protection
                                  domain)
        amd_iommu_size= [HW,X86-64]
                        Define the size of the aperture for the AMD IOMMU
                        driver. Possible values are:
                        '32M', '64M' (default), '128M', '256M', '512M', '1G'

        amijoy.map=     [HW,JOY] Amiga joystick support
                        Map of devices attached to JOY0DAT and JOY1DAT
                        Format: <a>,<b>
                        See also Documentation/kernel/input/joystick.txt

        analog.map=     [HW,JOY] Analog joystick and gamepad support
                        Specifies type or capabilities of an analog joystick
                        connected to one of 16 gameports
                        Format: <type1>,<type2>,..<type16>

        apc=            [HW,SPARC]
                        Power management functions (SPARCstation-4/5 + deriv.)
                        Format: noidle
                        Disable APC CPU standby support. SPARCstation-Fox does
                        not play well with APC CPU idle - disable it if you have
                        APC and your system crashes randomly.

        apic=           [APIC,i386] Advanced Programmable Interrupt Controller
                        Change the output verbosity whilst booting
                        Format: { quiet (default) | verbose | debug }
                        Change the amount of debugging information output
                        when initialising the APIC and IO-APIC components.

        apm=            [APM] Advanced Power Management
                        See header of arch/i386/kernel/apm.c.

        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
                        Format: <io>,<irq>,<nodeID>

        ataflop=        [HW,M68k]

        atarimouse=     [HW,MOUSE] Atari Mouse

        atascsi=        [HW,SCSI] Atari SCSI

        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
                        EzKey and similar keyboards

        atkbd.reset=    [HW] Reset keyboard during initialization

        atkbd.set=      [HW] Select keyboard code set
                        Format: <int> (2 = AT (default), 3 = PS/2)

        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
                        keyboards

        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
                        Format: <bool> (0 = real, 1 = synthetic (default))

        atkbd.softrepeat= [HW]
                        Use software keyboard repeat

        autotest        [IA64]

        baycom_epp=     [HW,AX25]
                        Format: <io>,<mode>

        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
                        Format: <io>,<mode>
                        See header of drivers/net/hamradio/baycom_par.c.

        baycom_ser_fdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
                        Format: <io>,<irq>,<mode>[,<baud>]
                        See header of drivers/net/hamradio/baycom_ser_fdx.c.

        baycom_ser_hdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
                        Format: <io>,<irq>,<mode>
                        See header of drivers/net/hamradio/baycom_ser_hdx.c.

        boot_delay=     Milliseconds to delay each printk during boot.
                        Values larger than 10 seconds (10000) are changed to
                        no delay (0).
                        Format: integer

        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
        bttv.radio=     Most important insmod options are available as
                        kernel args too.
        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
        bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST

        BusLogic=       [HW,SCSI]
                        See drivers/scsi/BusLogic.c, comment before function
                        BusLogic_ParseDriverOptions().

        c101=           [NET] Moxa C101 synchronous serial card

        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
                        Sometimes CPU hardware bugs make them report the cache
                        size incorrectly. The kernel will attempt work arounds
                        to fix known problems, but for some CPUs it is not
                        possible to determine what the correct size should be.
                        This option provides an override for these situations.

        security=       [SECURITY] Choose a security module to enable at boot.
                        If this boot parameter is not specified, only the first
                        security module asking for security registration will be
                        loaded. An invalid security module name will be treated
                        as if no module has been chosen.

        capability.disable=
                        [SECURITY] Disable capabilities.  This would normally
                        be used only if an alternative security model is to be
                        configured.  Potentially dangerous and should only be
                        used if you are entirely sure of the consequences.

        ccw_timeout_log [S390]
                        See Documentation/s390/CommonIO for details.

        cgroup_disable= [KNL] Disable a particular controller
                        Format: {name of the controller(s) to disable}
                                {Currently supported controllers - "memory"}

        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- check protection applied by kernel (includes
                                any implied execute protection).
                        1 -- check protection requested by application.
                        Default value is set via a kernel config option.
                        Value can be changed at runtime via
                                /selinux/checkreqprot.

        cio_ignore=     [S390]
                        See Documentation/s390/CommonIO for details.

        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
                        [Deprecated]
                        Forces specified clocksource (if available) to be used
                        when calculating gettimeofday(). If specified
                        clocksource is not available, it defaults to PIT.
                        Format: { pit | tsc | cyclone | pmtmr }

        clocksource=    [GENERIC_TIME] Override the default clocksource
                        Format: <string>
                        Override the default clocksource and use the clocksource
                        with the name specified.
                        Some clocksource names to choose from, depending on
                        the platform:
                        [all] jiffies (this is the base, fallback clocksource)
                        [ACPI] acpi_pm
                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
                                pxa_timer,timer3,32k_counter,timer0_1
                        [AVR32] avr32
                        [X86-32] pit,hpet,tsc,vmi-timer;
                                scx200_hrt on Geode; cyclone on IBM x440
                        [MIPS] MIPS
                        [PARISC] cr16
                        [S390] tod
                        [SH] SuperH
                        [SPARC64] tick
                        [X86-64] hpet,tsc

        clearcpuid=BITNUM [X86]
                        Disable CPUID feature X for the kernel. See
                        include/asm-x86/cpufeature.h for the valid bit numbers.
                        Note the Linux specific bits are not necessarily
                        stable over kernel options, but the vendor specific
                        ones should be.
                        Also note that user programs calling CPUID directly
                        or using the feature without checking anything
                        will still see it. This just prevents it from
                        being used by the kernel or shown in /proc/cpuinfo.
                        Also note the kernel might malfunction if you disable
                        some critical bits.

        code_bytes      [IA32/X86_64] How many bytes of object code to print
                        in an oops report.
                        Range: 0 - 8192
                        Default: 64

        disable_8254_timer
        enable_8254_timer
                        [IA32/X86_64] Disable/Enable interrupt 0 timer routing
                        over the 8254 in addition to over the IO-APIC. The
                        kernel tries to set a sensible default.

        hpet=           [X86-32,HPET] option to control HPET usage
                        Format: { enable (default) | disable | force }
                        disable: disable HPET and use PIT instead
                        force: allow force enabled of undocumented chips (ICH4,
                        VIA, nVidia)

        com20020=       [HW,NET] ARCnet - COM20020 chipset
                        Format:
                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]

        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
                        Format: <io>[,<irq>]

        com90xx=        [HW,NET]
                        ARCnet - COM90xx chipset (memory-mapped buffers)
                        Format: <io>[,<irq>[,<memstart>]]

        condev=         [HW,S390] console device
        conmode=

        console=        [KNL] Output console device and options.

                tty<n>  Use the virtual console device <n>.

                ttyS<n>[,options]
                ttyUSB0[,options]
                        Use the specified serial port.  The options are of
                        the form "bbbbpnf", where "bbbb" is the baud rate,
                        "p" is parity ("n", "o", or "e"), "n" is number of
                        bits, and "f" is flow control ("r" for RTS or
                        omit it).  Default is "9600n8".

                        See Documentation/serial-console.txt for more
                        information.  See
                        Documentation/networking/netconsole.txt for an
                        alternative.

                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address,
                        switching to the matching ttyS device later.  The
                        options are the same as for ttyS, above.

                If the device connected to the port is not a TTY but a braille
                device, prepend "brl," before the device type, for instance
                        console=brl,ttyS0
                For now, only VisioBraille is supported.

        earlycon=       [KNL] Output early console device and options.
                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address.
                        The options are the same as for ttyS, above.

        no_console_suspend
                        [HW] Never suspend the console
                        Disable suspending of consoles during suspend and
                        hibernate operations.  Once disabled, debugging
                        messages can reach various consoles while the rest
                        of the system is being put to sleep (ie, while
                        debugging driver suspend/resume hooks).  This may
                        not work reliably with all consoles, but is known
                        to work with serial and VGA consoles.

        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
                        Format:
                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

        crashkernel=nn[KMG]@ss[KMG]
                        [KNL] Reserve a chunk of physical memory to
                        hold a kernel to switch to with kexec on panic.

        crashkernel=range1:size1[,range2:size2,...][@offset]
                        [KNL] Same as above, but depends on the memory
                        in the running system. The syntax of range is
                        start-[end] where start and end are both
                        a memory unit (amount[KMG]). See also
                        Documentation/kdump/kdump.txt for a example.

        cs4232=         [HW,OSS]
                        Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>

        cs89x0_dma=     [HW,NET]
                        Format: <dma>

        cs89x0_media=   [HW,NET]
                        Format: { rj45 | aui | bnc }

        dasd=           [HW,NET]
                        See header of drivers/s390/block/dasd_devmap.c.

        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
                        (one device per port)
                        Format: <port#>,<type>
                        See also Documentation/input/joystick-parport.txt

        debug           [KNL] Enable kernel debugging (events log level).

        debug_locks_verbose=
                        [KNL] verbose self-tests
                        Format=<0|1>
                        Print debugging info while doing the locking API
                        self-tests.
                        We default to 0 (no extra messages), setting it to
                        1 will print _a lot_ more information - normally
                        only useful to kernel developers.

        debug_objects   [KNL] Enable object debugging

        decnet.addr=    [HW,NET]
                        Format: <area>[,<node>]
                        See also Documentation/networking/decnet.txt.

        vt.default_blu= [VT]
                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
                        Change the default blue palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_grn= [VT]
                        Format: <green0>,<green1>,<green2>,...,<green15>
                        Change the default green palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_red= [VT]
                        Format: <red0>,<red1>,<red2>,...,<red15>
                        Change the default red palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_utf8=
                        [VT]
                        Format=<0|1>
                        Set system-wide default UTF-8 mode for all tty's.
                        Default is 1, i.e. UTF-8 mode is enabled for all
                        newly opened terminals.

        dhash_entries=  [KNL]
                        Set number of hash buckets for dentry cache.

        digi=           [HW,SERIAL]
                        IO parameters + enable/disable command.

        digiepca=       [HW,SERIAL]
                        See drivers/char/README.epca and
                        Documentation/digiepca.txt.

        disable_mtrr_trim [X86, Intel and AMD only]
                        By default the kernel will trim any uncacheable
                        memory out of your available memory pool based on
                        MTRR settings.  This parameter disables that behavior,
                        possibly causing your machine to run very slowly.

        dmasound=       [HW,OSS] Sound subsystem buffers

        dscc4.setup=    [NET]

        dtc3181e=       [HW,SCSI]

        earlyprintk=    [X86-32,X86-64,SH,BLACKFIN]
                        earlyprintk=vga
                        earlyprintk=serial[,ttySn[,baudrate]]

                        Append ",keep" to not disable it when the real console
                        takes over.

                        Only vga or serial at a time, not both.

                        Currently only ttyS0 and ttyS1 are supported.

                        Interaction with the standard serial driver is not
                        very good.

                        The VGA output is eventually overwritten by the real
                        console.

        eata=           [HW,SCSI]

        edd=            [EDD]
                        Format: {"off" | "on" | "skip[mbr]"}

        eisa_irq_edge=  [PARISC,HW]
                        See header of drivers/parisc/eisa.c.

        elanfreq=       [X86-32]
                        See comment before function elanfreq_setup() in
                        arch/i386/kernel/cpu/cpufreq/elanfreq.c.

        elevator=       [IOSCHED]
                        Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
                        See Documentation/block/as-iosched.txt and
                        Documentation/block/deadline-iosched.txt for details.

        elfcorehdr=     [X86-32, X86_64]
                        Specifies physical address of start of kernel core
                        image elf header. Generally kexec loader will
                        pass this option to capture kernel.
                        See Documentation/kdump/kdump.txt for details.

        enforcing       [SELINUX] Set initial enforcing status.
                        Format: {"0" | "1"}
                        See security/selinux/Kconfig help text.
                        0 -- permissive (log only, no denials).
                        1 -- enforcing (deny and log).
                        Default value is 0.
                        Value can be changed at runtime via /selinux/enforce.

        es1371=         [HW,OSS]
                        Format: <spdif>,[<nomix>,[<amplifier>]]
                        See also header of sound/oss/es1371.c.

        ether=          [HW,NET] Ethernet cards parameters
                        This option is obsoleted by the "netdev=" option, which
                        has equivalent usage. See its documentation for details.

        eurwdt=         [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
                        Format: <io>[,<irq>]

        failslab=
        fail_page_alloc=
        fail_make_request=[KNL]
                        General fault injection mechanism.
                        Format: <interval>,<probability>,<space>,<times>
                        See also /Documentation/fault-injection/.

        fd_mcs=         [HW,SCSI]
                        See header of drivers/scsi/fd_mcs.c.

        fdomain=        [HW,SCSI]
                        See header of drivers/scsi/fdomain.c.

        floppy=         [HW]
                        See Documentation/floppy.txt.

        force_pal_cache_flush
                        [IA-64] Avoid check_sal_cache_flush which may hang on
                        buggy SAL_CACHE_FLUSH implementations. Using this
                        parameter will force ia64_sal_cache_flush to call
                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

        gamecon.map[2|3]=
                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
                        support via parallel port (up to 5 devices per port)
                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
                        See also Documentation/input/joystick-parport.txt

        gamma=          [HW,DRM]

        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
                        Format: off | on
                        default: on

        gdth=           [HW,SCSI]
                        See header of drivers/scsi/gdth.c.

        gpt             [EFI] Forces disk with valid GPT signature but
                        invalid Protective MBR to be treated as GPT.

        gvp11=          [HW,SCSI]

        hashdist=       [KNL,NUMA] Large hashes allocated during boot
                        are distributed across NUMA nodes.  Defaults on
                        for IA-64, off otherwise.
                        Format: 0 | 1 (for off | on)

        hcl=            [IA-64] SGI's Hardware Graph compatibility layer

        hd=             [EIDE] (E)IDE hard drive subsystem geometry
                        Format: <cyl>,<head>,<sect>

        hd?=            [HW] (E)IDE subsystem
        hd?lun=         See Documentation/ide/ide.txt.

        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
                        size of <nn>. This works even on boxes that have no
                        highmem otherwise. This also works to reduce highmem
                        size on bigger boxes.

        highres=        [KNL] Enable/disable high resolution timer mode.
                        Valid parameters: "on", "off"
                        Default: "on"

        hisax=          [HW,ISDN]
                        See Documentation/isdn/README.HiSax.

        hugepages=      [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
        hugepagesz=     [HW,IA-64,PPC] The size of the HugeTLB pages.

        i8042.direct    [HW] Put keyboard port into non-translated mode
        i8042.dumbkbd   [HW] Pretend that controller can only read data from
                             keyboard and cannot control its state
                             (Don't attempt to blink the leds)
        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
        i8042.nokbd     [HW] Don't check/create keyboard port
        i8042.noloop    [HW] Disable the AUX Loopback command while probing
                             for the AUX port
        i8042.nomux     [HW] Don't check presence of an active multiplexing
                             controller
        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
                             controllers
        i8042.panicblink=
                        [HW] Frequency with which keyboard LEDs should blink
                             when kernel panics (default is 0.5 sec)
        i8042.reset     [HW] Reset the controller during init and cleanup
        i8042.unlock    [HW] Unlock (ignore) the keylock

        i810=           [HW,DRM]

        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
                        indicates that the driver is running on unsupported
                        hardware.
        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
                        does not match list of supported models.
        i8k.power_status
                        [HW] Report power status in /proc/i8k
                        (disabled by default)
        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
                        capability is set.

        ibmmcascsi=     [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
                        See Documentation/mca.txt.

        icn=            [HW,ISDN]
                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]

        ide=            [HW] (E)IDE subsystem
                        Format: ide=nodma or ide=doubler
                        See Documentation/ide/ide.txt.

        idebus=         [HW] (E)IDE subsystem - VLB/PCI bus speed
                        See Documentation/ide/ide.txt.

        idle=           [X86]
                        Format: idle=poll or idle=mwait
                        Poll forces a polling idle loop that can slightly improves the performance
                        of waking up a idle CPU, but will use a lot of power and make the system
                        run hot. Not recommended.
                        idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
                        to not use it because it doesn't save as much power as a normal idle
                        loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
                        as idle=poll.

        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
                        Claim all unknown PCI IDE storage controllers.

        ignore_loglevel [KNL]
                        Ignore loglevel setting - this will print /all/
                        kernel messages to the console. Useful for debugging.

        ihash_entries=  [KNL]
                        Set number of hash buckets for inode cache.

        in2000=         [HW,SCSI]
                        See header of drivers/scsi/in2000.c.

        init=           [KNL]
                        Format: <full_path>
                        Run specified binary instead of /sbin/init as init
                        process.

        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
                        for working out where the kernel is dying during
                        startup.

        initrd=         [BOOT] Specify the location of the initial ramdisk

        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
                        Format: <irq>

        inttest=        [IA64]

        iommu=          [x86]
                off
                force
                noforce
                biomerge
                panic
                nopanic
                merge
                nomerge
                forcesac
                soft


        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
                off
                        Disable intel iommu driver.
                igfx_off [Default Off]
                        By default, gfx is mapped as normal device. If a gfx
                        device has a dedicated DMAR unit, the DMAR unit is
                        bypassed by not enabling DMAR with this option. In
                        this case, gfx device will use physical address for
                        DMA.
                forcedac [x86_64]
                        With this option iommu will not optimize to look
                        for io virtual address below 32 bit forcing dual
                        address cycle on pci bus for cards supporting greater
                        than 32 bit addressing. The default is to look
                        for translation below 32 bit and if not available
                        then look in the higher range.
                strict [Default Off]
                        With this option on every unmap_single operation will
                        result in a hardware IOTLB flush operation as opposed
                        to batching them for performance.

        io_delay=       [X86-32,X86-64] I/O delay method
                0x80
                        Standard port 0x80 based delay
                0xed
                        Alternate port 0xed based delay (needed on some systems)
                udelay
                        Simple two microseconds delay
                none
                        No delay

        io7=            [HW] IO7 for Marvel based alpha systems
                        See comment before marvel_specify_io7 in
                        arch/alpha/kernel/core_marvel.c.

        ip=             [IP_PNP]
                        See Documentation/filesystems/nfsroot.txt.

        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
                        See comment before ip2_setup() in
                        drivers/char/ip2/ip2base.c.

        ips=            [HW,SCSI] Adaptec / IBM ServeRAID controller
                        See header of drivers/scsi/ips.c.

        ports=          [IP_VS_FTP] IPVS ftp helper module
                        Default is 21.
                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
                        may be specified.
                        Format: <port>,<port>....

        irqfixup        [HW]
                        When an interrupt is not handled search all handlers
                        for it. Intended to get systems with badly broken
                        firmware running.

        irqpoll         [HW]
                        When an interrupt is not handled search all handlers
                        for it. Also check all handlers each timer
                        interrupt. Intended to get systems with badly broken
                        firmware running.

        isapnp=         [ISAPNP]
                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>

        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
                        Format:
                        <cpu number>,...,<cpu number>
                        or
                        <cpu number>-<cpu number>  (must be a positive range in ascending order)
                        or a mixture
                        <cpu number>,...,<cpu number>-<cpu number>
                        This option can be used to specify one or more CPUs
                        to isolate from the general SMP balancing and scheduling
                        algorithms. The only way to move a process onto or off
                        an "isolated" CPU is via the CPU affinity syscalls.
                        <cpu number> begins at 0 and the maximum value is
                        "number of CPUs in system - 1".

                        This option is the preferred way to isolate CPUs. The
                        alternative -- manually setting the CPU mask of all
                        tasks in the system -- can cause problems and
                        suboptimal load balancer performance.

        iucv=           [HW,NET]

        js=             [HW,JOY] Analog joystick
                        See Documentation/input/joystick.txt.

        kernelcore=nn[KMG]      [KNL,X86-32,IA-64,PPC,X86-64] This parameter
                        specifies the amount of memory usable by the kernel
                        for non-movable allocations.  The requested amount is
                        spread evenly throughout all nodes in the system. The
                        remaining memory in each node is used for Movable
                        pages. In the event, a node is too small to have both
                        kernelcore and Movable pages, kernelcore pages will
                        take priority and other nodes will have a larger number
                        of kernelcore pages.  The Movable zone is used for the
                        allocation of pages that may be reclaimed or moved
                        by the page migration subsystem.  This means that
                        HugeTLB pages may not be allocated from this zone.
                        Note that allocations like PTEs-from-HighMem still
                        use the HighMem zone if it exists, and the Normal
                        zone if it does not.

        movablecore=nn[KMG]     [KNL,X86-32,IA-64,PPC,X86-64] This parameter
                        is similar to kernelcore except it specifies the
                        amount of memory used for migratable allocations.
                        If both kernelcore and movablecore is specified,
                        then kernelcore will be at *least* the specified
                        value but may be more. If movablecore on its own
                        is specified, the administrator must be careful
                        that the amount of memory usable for all allocations
                        is not too small.

        keepinitrd      [HW,ARM]

        kstack=N        [X86-32,X86-64] Print N words from the kernel stack
                        in oops dumps.

        kgdboc=         [HW] kgdb over consoles.
                        Requires a tty driver that supports console polling.
                        (only serial suported for now)
                        Format: <serial_device>[,baud]

        l2cr=           [PPC]

        l3cr=           [PPC]

        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
                        disabled it.

        lapic_timer_c2_ok       [X86-32,x86-64,APIC] trust the local apic timer in
                        C2 power state.

        libata.dma=     [LIBATA] DMA control
                        libata.dma=0      Disable all PATA and SATA DMA
                        libata.dma=1      PATA and SATA Disk DMA only
                        libata.dma=2      ATAPI (CDROM) DMA only
                        libata.dma=4      Compact Flash DMA only 
                        Combinations also work, so libata.dma=3 enables DMA
                        for disks and CDROMs, but not CFs.

        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
                        when set.
                        Format: <int>

        libata.force=   [LIBATA] Force configurations.  The format is comma
                        separated list of "[ID:]VAL" where ID is
                        PORT[:DEVICE].  PORT and DEVICE are decimal numbers
                        matching port, link or device.  Basically, it matches
                        the ATA ID string printed on console by libata.  If
                        the whole ID part is omitted, the last PORT and DEVICE
                        values are used.  If ID hasn't been specified yet, the
                        configuration applies to all ports, links and devices.

                        If only DEVICE is omitted, the parameter applies to
                        the port and all links and devices behind it.  DEVICE
                        number of 0 either selects the first device or the
                        first fan-out link behind PMP device.  It does not
                        select the host link.  DEVICE number of 15 selects the
                        host link and device attached to it.

                        The VAL specifies the configuration to force.  As long
                        as there's no ambiguity shortcut notation is allowed.
                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
                        The following configurations can be forced.

                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
                          Any ID with matching PORT is used.

                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.

                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
                          udma[/][16,25,33,44,66,100,133] notation is also
                          allowed.

                        * [no]ncq: Turn on or off NCQ.

                        If there are multiple matching configurations changing
                        the same attribute, the last one is used.

        load_ramdisk=   [RAM] List of ramdisks to load from floppy
                        See Documentation/ramdisk.txt.

        lockd.nlm_grace_period=P  [NFS] Assign grace period.
                        Format: <integer>

        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
                        Format: <integer>

        lockd.nlm_timeout=T     [NFS] Assign timeout value.
                        Format: <integer>

        lockd.nlm_udpport=M     [NFS] Assign UDP port.
                        Format: <integer>

        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
                        Format: <irq>

        loglevel=       All Kernel Messages with a loglevel smaller than the
                        console loglevel will be printed to the console. It can
                        also be changed with klogd or other programs. The
                        loglevels are defined as follows:

                        0 (KERN_EMERG)          system is unusable
                        1 (KERN_ALERT)          action must be taken immediately
                        2 (KERN_CRIT)           critical conditions
                        3 (KERN_ERR)            error conditions
                        4 (KERN_WARNING)        warning conditions
                        5 (KERN_NOTICE)         normal but significant condition
                        6 (KERN_INFO)           informational
                        7 (KERN_DEBUG)          debug-level messages

        log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
                        Format: { n | nk | nM }
                        n must be a power of two.  The default size
                        is set in the kernel config file.

        logo.nologo     [FB] Disables display of the built-in Linux logo.
                        This may be used to provide more screen space for
                        kernel log messages and is useful when debugging
                        kernel boot problems.

        lp=0            [LP]    Specify parallel ports to use, e.g,
        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
        lp=reset                first parallel port). 'lp=0' disables the
        lp=auto                 printer driver. 'lp=reset' (which can be
                                specified in addition to the ports) causes
                                attached printers to be reset. Using
                                lp=port1,port2,... specifies the parallel ports
                                to associate lp devices with, starting with
                                lp0. A port specification may be 'none' to skip
                                that lp device, or a parport name such as
                                'parport0'. Specifying 'lp=auto' instead of a
                                port specification list means that device IDs
                                from each port should be examined, to see if
                                an IEEE 1284-compliant printer is attached; if
                                so, the driver will manage that printer.
                                See also header of drivers/char/lp.c.

        lpj=n           [KNL]
                        Sets loops_per_jiffy to given constant, thus avoiding
                        time-consuming boot-time autodetection (up to 250 ms per
                        CPU). 0 enables autodetection (default). To determine
                        the correct value for your kernel, boot with normal
                        autodetection and see what value is printed. Note that
                        on SMP systems the preset will be applied to all CPUs,
                        which is likely to cause problems if your CPUs need
                        significantly divergent settings. An incorrect value
                        will cause delays in the kernel to be wrong, leading to
                        unpredictable I/O errors and other breakage. Although
                        unlikely, in the extreme case this might damage your
                        hardware.

        ltpc=           [NET]
                        Format: <io>,<irq>,<dma>

        mac5380=        [HW,SCSI] Format:
                        <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>

        machvec=        [IA64] Force the use of a particular machine-vector
                        (machvec) in a generic kernel.
                        Example: machvec=hpzx1_swiotlb

        max_loop=       [LOOP] Maximum number of loopback devices that can
                        be mounted
                        Format: <1-256>

        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
                        should make use of.  maxcpus=n : n >= 0 limits the
                        kernel to using 'n' processors.  n=0 is a special case,
                        it is equivalent to "nosmp", which also disables
                        the IO APIC.

        max_addr=[KMG]  [KNL,BOOT,ia64] All physical memory greater than or
                        equal to this physical address is ignored.

        max_luns=       [SCSI] Maximum number of LUNs to probe.
                        Should be between 1 and 2^32-1.

        max_report_luns=
                        [SCSI] Maximum number of LUNs received.
                        Should be between 1 and 16384.

        mcatest=        [IA-64]

        mce             [X86-32] Machine Check Exception

        mce=option      [X86-64] See Documentation/x86_64/boot-options.txt

        md=             [HW] RAID subsystems devices and level
                        See Documentation/md.txt.

        mdacon=         [MDA]
                        Format: <first>,<last>
                        Specifies range of consoles to be captured by the MDA.

        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
                        Amount of memory to be used when the kernel is not able
                        to see the whole system memory or for test.
                        [X86-32] Use together with memmap= to avoid physical
                        address space collisions. Without memmap= PCI devices
                        could be placed at addresses belonging to unused RAM.

        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
                        memory.

        memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
                        E820 memory map, as specified by the user.
                        Such memmap=exactmap lines can be constructed based on
                        BIOS output or other requirements. See the memmap=nn@ss
                        option description.

        memmap=nn[KMG]@ss[KMG]
                        [KNL] Force usage of a specific region of memory
                        Region of memory to be used, from ss to ss+nn.

        memmap=nn[KMG]#ss[KMG]
                        [KNL,ACPI] Mark specific memory as ACPI data.
                        Region of memory to be used, from ss to ss+nn.

        memmap=nn[KMG]$ss[KMG]
                        [KNL,ACPI] Mark specific memory as reserved.
                        Region of memory to be used, from ss to ss+nn.
                        Example: Exclude memory from 0x18690000-0x1869ffff
                                 memmap=64K$0x18690000
                                 or
                                 memmap=0x10000$0x18690000

        memtest=        [KNL,X86_64] Enable memtest
                        Format: <integer>
                        range: 0,4 : pattern number
                        default : 0 <disable>

        meye.*=         [HW] Set MotionEye Camera parameters
                        See Documentation/video4linux/meye.txt.

        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
                        Multi-Function General Purpose Timers on AMD Geode
                        platforms.

        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
                        the BIOS has incorrectly applied a workaround. TinyBIOS
                        version 0.98 is known to be affected, 0.99 fixes the
                        problem by letting the user disable the workaround.

        mga=            [HW,DRM]

        mousedev.tap_time=
                        [MOUSE] Maximum time between finger touching and
                        leaving touchpad surface for touch to be considered
                        a tap and be reported as a left button click (for
                        touchpads working in absolute mode only).
                        Format: <msecs>
        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
                        reporting absolute coordinates, such as tablets
        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
                        reporting absolute coordinates, such as tablets

        mpu401=         [HW,OSS]
                        Format: <io>,<irq>

        MTD_Partition=  [MTD]
                        Format: <name>,<region-number>,<size>,<offset>

        MTD_Region=     [MTD] Format:
                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]

        mtdparts=       [MTD]
                        See drivers/mtd/cmdlinepart.c.

        mtouchusb.raw_coordinates=
                        [HW] Make the MicroTouch USB driver use raw coordinates
                        ('y', default) or cooked coordinates ('n')

        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card

        NCR_D700=       [HW,SCSI]
                        See header of drivers/scsi/NCR_D700.c.

        ncr5380=        [HW,SCSI]

        ncr53c400=      [HW,SCSI]

        ncr53c400a=     [HW,SCSI]

        ncr53c406a=     [HW,SCSI]

        ncr53c8xx=      [HW,SCSI]

        netdev=         [NET] Network devices parameters
                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
                        Note that mem_start is often overloaded to mean
                        something different and driver-specific.
                        This usage is only documented in each driver source
                        file if at all.

        nfsaddrs=       [NFS]
                        See Documentation/filesystems/nfsroot.txt.

        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
                        See Documentation/filesystems/nfsroot.txt.

        nfs.callback_tcpport=
                        [NFS] set the TCP port on which the NFSv4 callback
                        channel should listen.

        nfs.idmap_cache_timeout=
                        [NFS] set the maximum lifetime for idmapper cache
                        entries.

        nfs.enable_ino64=
                        [NFS] enable 64-bit inode numbers.
                        If zero, the NFS client will fake up a 32-bit inode
                        number for the readdir() and stat() syscalls instead
                        of returning the full 64-bit number.
                        The default is to return 64-bit inode numbers.

        nmi_debug=      [KNL,AVR32] Specify one or more actions to take
                        when a NMI is triggered.
                        Format: [state][,regs][,debounce][,die]

        nmi_watchdog=   [KNL,BUGS=X86-32] Debugging features for SMP kernels

        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
                        emulation library even if a 387 maths coprocessor
                        is present.

        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
                        caches in the slab allocator.  Saves per-node memory,
                        but will impact performance.

        noalign         [KNL,ARM]

        noapic          [SMP,APIC] Tells the kernel to not make use of any
                        IOAPICs that may be present in the system.

        nobats          [PPC] Do not use BATs for mapping kernel lowmem
                        on "Classic" PPC cores.

        nocache         [ARM]

        nodelayacct     [KNL] Disable per-task delay accounting

        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.

        noefi           [X86-32,X86-64] Disable EFI runtime services support.

        noexec          [IA-64]

        noexec          [X86-32,X86-64]
                        On X86-32 available only on PAE configured kernels.
                        noexec=on: enable non-executable mappings (default)
                        noexec=off: disable non-executable mappings

        noexec32        [X86-64]
                        This affects only 32-bit executables.
                        noexec32=on: enable non-executable mappings (default)
                                read doesn't imply executable mappings
                        noexec32=off: disable non-executable mappings
                                read implies executable mappings

        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
                        register save and restore. The kernel will only save
                        legacy floating-point registers on task switch.

        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction

        nohlt           [BUGS=ARM]

        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
                        instruction doesn't work correctly and not to
                        use it.

        nohalt          [IA-64] Tells the kernel not to use the power saving
                        function PAL_HALT_LIGHT when idle. This increases
                        power-consumption. On the positive side, it reduces
                        interrupt wake-up latency, which may improve performance
                        in certain environments such as networked servers or
                        real-time systems.

        nohz=           [KNL] Boottime enable/disable dynamic ticks
                        Valid arguments: on, off
                        Default: on

        noirqbalance    [X86-32,SMP,KNL] Disable kernel irq balancing

        noirqdebug      [X86-32] Disables the code which attempts to detect and
                        disable unhandled interrupt sources.

        no_timer_check  [X86-32,X86_64,APIC] Disables the code which tests for
                        broken timer IRQ sources.

        noisapnp        [ISAPNP] Disables ISA PnP code.

        noinitrd        [RAM] Tells the kernel not to load any configured
                        initial RAM disk.

        nointroute      [IA-64]

        nojitter        [IA64] Disables jitter checking for ITC timers.

        nolapic         [X86-32,APIC] Do not enable or use the local APIC.

        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.

        noltlbs         [PPC] Do not use large page/tlb entries for kernel
                        lowmem mapping on PPC40x.

        nomca           [IA-64] Disable machine check abort handling

        nomce           [X86-32] Machine Check Exception

        nomfgpt         [X86-32] Disable Multi-Function General Purpose
                        Timer usage (for AMD Geode machines).

        noreplace-paravirt      [X86-32,PV_OPS] Don't patch paravirt_ops

        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
                        with UP alternatives

        noresidual      [PPC] Don't use residual data on PReP machines.

        noresume        [SWSUSP] Disables resume and restores original swap
                        space.

        no-scroll       [VGA] Disables scrollback.
                        This is required for the Braillex ib80-piezo Braille
                        reader made by F.H. Papenmeier (Germany).

        nosbagart       [IA-64]

        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.

        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
                        and disable the IO APIC.  legacy for "maxcpus=0".

        nosoftlockup    [KNL] Disable the soft-lockup detector.

        nosync          [HW,M68K] Disables sync negotiation for all devices.

        notsc           [BUGS=X86-32] Disable Time Stamp Counter

        nousb           [USB] Disable the USB subsystem

        nowb            [ARM]

        nptcg=          [IA64] Override max number of concurrent global TLB
                        purges which is reported from either PAL_VM_SUMMARY or
                        SAL PALO.

        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
                        one of ['zone', 'node', 'default'] can be specified
                        This can be set from sysctl after boot.
                        See Documentation/sysctl/vm.txt for details.

        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.

        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
                        Rather than timing out after 20 ms if an EC
                        command is not properly ACKed, override the length
                        of the timeout.  We have interrupts disabled while
                        waiting for the ACK, so if this is set too high
                        interrupts *may* be lost!

        opl3=           [HW,OSS]
                        Format: <io>

        oprofile.timer= [HW]
                        Use timer interrupt instead of performance counters

        osst=           [HW,SCSI] SCSI Tape Driver
                        Format: <buffer_size>,<write_threshold>
                        See also Documentation/scsi/st.txt.

        panic=          [KNL] Kernel behaviour on panic
                        Format: <timeout>

        parkbd.port=    [HW] Parallel port number the keyboard adapter is
                        connected to, default is 0.
                        Format: <parport#>
        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
                        0 for XT, 1 for AT (default is AT).
                        Format: <mode>

        parport=        [HW,PPT] Specify parallel ports. 0 disables.
                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
                        Use 'auto' to force the driver to use any
                        IRQ/DMA settings detected (the default is to
                        ignore detected IRQ/DMA settings because of
                        possible conflicts). You can specify the base
                        address, IRQ, and DMA settings; IRQ and DMA
                        should be numbers, or 'auto' (for using detected
                        settings on that particular port), or 'nofifo'
                        (to avoid using a FIFO even if it is detected).
                        Parallel ports are assigned in the order they
                        are specified on the command line, starting
                        with parport0.

        parport_init_mode=      [HW,PPT]
                        Configure VIA parallel port to operate in
                        a specific mode. This is necessary on Pegasos
                        computer where firmware has no options for setting
                        up parallel port mode and sets it to spp.
                        Currently this function knows 686a and 8231 chips.
                        Format: [spp|ps2|epp|ecp|ecpepp]

        pas2=           [HW,OSS] Format:
                        <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>

        pas16=          [HW,SCSI]
                        See header of drivers/scsi/pas16.c.

        pause_on_oops=
                        Halt all CPUs after the first oops has been printed for
                        the specified number of seconds.  This is to be used if
                        your oopses keep scrolling off the screen.

        pcbit=          [HW,ISDN]

        pcd.            [PARIDE]
                        See header of drivers/block/paride/pcd.c.
                        See also Documentation/paride.txt.

        pci=option[,option...]  [PCI] various PCI subsystem options:
                off             [X86-32] don't probe for the PCI bus
                bios            [X86-32] force use of PCI BIOS, don't access
                                the hardware directly. Use this if your machine
                                has a non-standard PCI host bridge.
                nobios          [X86-32] disallow use of PCI BIOS, only direct
                                hardware access methods are allowed. Use this
                                if you experience crashes upon bootup and you
                                suspect they are caused by the BIOS.
                conf1           [X86-32] Force use of PCI Configuration
                                Mechanism 1.
                conf2           [X86-32] Force use of PCI Configuration
                                Mechanism 2.
                noaer           [PCIE] If the PCIEAER kernel config parameter is
                                enabled, this kernel boot option can be used to
                                disable the use of PCIE advanced error reporting.
                nodomains       [PCI] Disable support for multiple PCI
                                root domains (aka PCI segments, in ACPI-speak).
                nommconf        [X86-32,X86_64] Disable use of MMCONFIG for PCI
                                Configuration
                nomsi           [MSI] If the PCI_MSI kernel config parameter is
                                enabled, this kernel boot option can be used to
                                disable the use of MSI interrupts system-wide.
                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
                                routing table. These calls are known to be buggy
                                on several machines and they hang the machine
                                when used, but on other computers it's the only
                                way to get the interrupt routing table. Try
                                this option if the kernel is unable to allocate
                                IRQs or discover secondary PCI buses on your
                                motherboard.
                rom             [X86-32] Assign address space to expansion ROMs.
                                Use with caution as certain devices share
                                address decoders between ROMs and other
                                resources.
                irqmask=0xMMMM  [X86-32] Set a bit mask of IRQs allowed to be
                                assigned automatically to PCI devices. You can
                                make the kernel exclude IRQs of your ISA cards
                                this way.
                pirqaddr=0xAAAAA        [X86-32] Specify the physical address
                                of the PIRQ table (normally generated
                                by the BIOS) if it is outside the
                                F0000h-100000h range.
                lastbus=N       [X86-32] Scan all buses thru bus #N. Can be
                                useful if the kernel is unable to find your
                                secondary buses and you want to tell it
                                explicitly which ones they are.
                assign-busses   [X86-32] Always assign all PCI bus
                                numbers ourselves, overriding
                                whatever the firmware may have done.
                usepirqmask     [X86-32] Honor the possible IRQ mask stored
                                in the BIOS $PIR table. This is needed on
                                some systems with broken BIOSes, notably
                                some HP Pavilion N5400 and Omnibook XE3
                                notebooks. This will have no effect if ACPI
                                IRQ routing is enabled.
                noacpi          [X86-32] Do not use ACPI for IRQ routing
                                or for PCI scanning.
                use_crs         [X86-32] Use _CRS for PCI resource
                                allocation.
                routeirq        Do IRQ routing for all PCI devices.
                                This is normally done in pci_enable_device(),
                                so this option is a temporary workaround
                                for broken drivers that don't call it.
                skip_isa_align  [X86] do not align io start addr, so can
                                handle more pci cards
                firmware        [ARM] Do not re-enumerate the bus but instead
                                just use the configuration from the
                                bootloader. This is currently used on
                                IXP2000 systems where the bus has to be
                                configured a certain way for adjunct CPUs.
                noearly         [X86] Don't do any early type 1 scanning.
                                This might help on some broken boards which
                                machine check when some devices' config space
                                is read. But various workarounds are disabled
                                and some IOMMU drivers will not work.
                bfsort          Sort PCI devices into breadth-first order.
                                This sorting is done to get a device
                                order compatible with older (<= 2.4) kernels.
                nobfsort        Don't sort PCI devices into breadth-first order.
                cbiosize=nn[KMG]        The fixed amount of bus space which is
                                reserved for the CardBus bridge's IO window.
                                The default value is 256 bytes.
                cbmemsize=nn[KMG]       The fixed amount of bus space which is
                                reserved for the CardBus bridge's memory
                                window. The default value is 64 megabytes.

        pcmv=           [HW,PCMCIA] BadgePAD 4

        pd.             [PARIDE]
                        See Documentation/paride.txt.

        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
                        boot time.
                        Format: { 0 | 1 }
                        See arch/parisc/kernel/pdc_chassis.c

        pf.             [PARIDE]
                        See Documentation/paride.txt.

        pg.             [PARIDE]
                        See Documentation/paride.txt.

        pirq=           [SMP,APIC] Manual mp-table setup
                        See Documentation/i386/IO-APIC.txt.

        plip=           [PPT,NET] Parallel port network link
                        Format: { parport<nr> | timid | 0 }
                        See also Documentation/parport.txt.

        pnpacpi=        [ACPI]
                        { off }

        pnpbios=        [ISAPNP]
                        { on | off | curr | res | no-curr | no-res }

        pnp_reserve_irq=
                        [ISAPNP] Exclude IRQs for the autoconfiguration

        pnp_reserve_dma=
                        [ISAPNP] Exclude DMAs for the autoconfiguration

        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
                        Ranges are in pairs (I/O port base and size).

        pnp_reserve_mem=
                        [ISAPNP] Exclude memory regions for the
                        autoconfiguration.
                        Ranges are in pairs (memory base and size).

        print-fatal-signals=
                        [KNL] debug: print fatal signals
                        print-fatal-signals=1: print segfault info to
                        the kernel console.
                        default: off.

        printk.time=    Show timing data prefixed to each printk message line
                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

        profile=        [KNL] Enable kernel profiling via /proc/profile
                        Format: [schedule,]<number>
                        Param: "schedule" - profile schedule points.
                        Param: <number> - step/bucket size as a power of 2 for
                                statistical time based profiling.
                        Param: "sleep" - profile D-state sleeping (millisecs).
                                Requires CONFIG_SCHEDSTATS
                        Param: "kvm" - profile VM exits.

        processor.max_cstate=   [HW,ACPI]
                        Limit processor to maximum C-state
                        max_cstate=9 overrides any DMI blacklist limit.

        processor.nocst [HW,ACPI]
                        Ignore the _CST method to determine C-states,
                        instead using the legacy FADT method

        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
                        before loading.
                        See Documentation/ramdisk.txt.

        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
                        probe for; one of (bare|imps|exps|lifebook|any).
        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
                        per second.
        psmouse.resetafter=     [HW,MOUSE]
                        Try to reset the device after so many bad packets
                        (0 = never).
        psmouse.resolution=
                        [HW,MOUSE] Set desired mouse resolution, in dpi.
        psmouse.smartscroll=
                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
                        0 = disabled, 1 = enabled (default).

        pss=            [HW,OSS] Personal Sound System (ECHO ESC614)
                        Format:
                        <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>

        pt.             [PARIDE]
                        See Documentation/paride.txt.

        pty.legacy_count=
                        [KNL] Number of legacy pty's. Overwrites compiled-in
                        default number.

        quiet           [KNL] Disable most log messages

        r128=           [HW,DRM]

        raid=           [HW,RAID]
                        See Documentation/md.txt.

        ramdisk_blocksize=      [RAM]
                        See Documentation/ramdisk.txt.

        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
                        See Documentation/ramdisk.txt.

        rcupdate.blimit=        [KNL,BOOT]
                        Set maximum number of finished RCU callbacks to process
                        in one batch.

        rcupdate.qhimark=       [KNL,BOOT]
                        Set threshold of queued
                        RCU callbacks over which batch limiting is disabled.

        rcupdate.qlowmark=      [KNL,BOOT]
                        Set threshold of queued RCU callbacks below which
                        batch limiting is re-enabled.

        rdinit=         [KNL]
                        Format: <full_path>
                        Run specified binary instead of /init from the ramdisk,
                        used for early userspace startup. See initrd.

        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c                   

        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area

        reservetop=     [X86-32]
                        Format: nn[KMG]
                        Reserves a hole at the top of the kernel virtual
                        address space.

        reset_devices   [KNL] Force drivers to reset the underlying device
                        during initialization.

        resume=         [SWSUSP]
                        Specify the partition device for software suspend

        resume_offset=  [SWSUSP]
                        Specify the offset from the beginning of the partition
                        given by "resume=" at which the swap header is located,
                        in <PAGE_SIZE> units (needed only for swap files).
                        See  Documentation/power/swsusp-and-swap-files.txt

        retain_initrd   [RAM] Keep initrd memory after extraction

        rhash_entries=  [KNL,NET]
                        Set number of hash buckets for route cache

        riscom8=        [HW,SERIAL]
                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]

        ro              [KNL] Mount root device read-only on boot

        root=           [KNL] Root filesystem

        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
                        mount the root filesystem

        rootflags=      [KNL] Set root filesystem mount option string

        rootfstype=     [KNL] Set root filesystem type

        rootwait        [KNL] Wait (indefinitely) for root device to show up.
                        Useful for devices that are detected asynchronously
                        (e.g. USB and MMC devices).

        root_plug.vendor_id=
                        [ROOTPLUG] Override the default vendor ID

        root_plug.product_id=
                        [ROOTPLUG] Override the default product ID

        root_plug.debug=
                        [ROOTPLUG] Enable debugging output

        rw              [KNL] Mount root device read-write on boot

        S               [KNL] Run init in single mode

        sa1100ir        [NET]
                        See drivers/net/irda/sa1100_ir.c.

        sbni=           [NET] Granch SBNI12 leased line adapter

        sc1200wdt=      [HW,WDT] SC1200 WDT (watchdog) driver
                        Format: <io>[,<timeout>[,<isapnp>]]

        scsi_debug_*=   [SCSI]
                        See drivers/scsi/scsi_debug.c.

        scsi_default_dev_flags=
                        [SCSI] SCSI default device flags
                        Format: <integer>

        scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
                        Format: <vendor>:<model>:<flags>
                        (flags are integer value)

        scsi_logging_level=     [SCSI] a bit mask of logging levels
                        See drivers/scsi/scsi_logging.h for bits.  Also
                        settable via sysctl at dev.scsi.logging_level
                        (/proc/sys/dev/scsi/logging_level).
                        There is also a nice 'scsi_logging_level' script in the
                        S390-tools package, available for download at
                        http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html

        scsi_mod.scan=  [SCSI] sync (default) scans SCSI busses as they are
                        discovered.  async scans them in kernel threads,
                        allowing boot to proceed.  none ignores them, expecting
                        user space to do the scan.

        selinux         [SELINUX] Disable or enable SELinux at boot time.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- disable.
                        1 -- enable.
                        Default value is set via kernel config option.
                        If enabled at boot time, /selinux/disable can be used
                        later to disable prior to initial policy load.

        selinux_compat_net =
                        [SELINUX] Set initial selinux_compat_net flag value.
                        Format: { "0" | "1" }
                        0 -- use new secmark-based packet controls
                        1 -- use legacy packet controls
                        Default value is 0 (preferred).
                        Value can be changed at runtime via
                        /selinux/compat_net.

        serialnumber    [BUGS=X86-32]

        shapers=        [NET]
                        Maximal number of shapers.

        sim710=         [SCSI,HW]
                        See header of drivers/scsi/sim710.c.

        simeth=         [IA-64]
        simscsi=

        slram=          [HW,MTD]

        slub_debug[=options[,slabs]]    [MM, SLUB]
                        Enabling slub_debug allows one to determine the
                        culprit if slab objects become corrupted. Enabling
                        slub_debug can create guard zones around objects and
                        may poison objects when not in use. Also tracks the
                        last alloc / free. For more information see
                        Documentation/vm/slub.txt.

        slub_max_order= [MM, SLUB]
                        Determines the maximum allowed order for slabs.
                        A high setting may cause OOMs due to memory
                        fragmentation. For more information see
                        Documentation/vm/slub.txt.

        slub_min_objects=       [MM, SLUB]
                        The minimum number of objects per slab. SLUB will
                        increase the slab order up to slub_max_order to
                        generate a sufficiently large slab able to contain
                        the number of objects indicated. The higher the number
                        of objects the smaller the overhead of tracking slabs
                        and the less frequently locks need to be acquired.
                        For more information see Documentation/vm/slub.txt.

        slub_min_order= [MM, SLUB]
                        Determines the mininum page order for slabs. Must be
                        lower than slub_max_order.
                        For more information see Documentation/vm/slub.txt.

        slub_nomerge    [MM, SLUB]
                        Disable merging of slabs with similar size. May be
                        necessary if there is some reason to distinguish
                        allocs to different slabs. Debug options disable
                        merging on their own.
                        For more information see Documentation/vm/slub.txt.

        smart2=         [HW]
                        Format: <io1>[,<io2>[,...,<io8>]]

        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
                        attempt to substitute SMP alternatives once at boot.

        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
        smsc-ircc2.ircc_irq=    [HW] IRQ line
        smsc-ircc2.ircc_dma=    [HW] DMA channel
        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
                                0: Toshiba Satellite 1800 (GP data pin select)
                                1: Fast pin select (default)
                                2: ATC IRMode

        snd-ad1816a=    [HW,ALSA]

        snd-ad1848=     [HW,ALSA]

        snd-ali5451=    [HW,ALSA]

        snd-als100=     [HW,ALSA]

        snd-als4000=    [HW,ALSA]

        snd-azt2320=    [HW,ALSA]

        snd-cmi8330=    [HW,ALSA]

        snd-cmipci=     [HW,ALSA]

        snd-cs4231=     [HW,ALSA]

        snd-cs4232=     [HW,ALSA]

        snd-cs4236=     [HW,ALSA]

        snd-cs4281=     [HW,ALSA]

        snd-cs46xx=     [HW,ALSA]

        snd-dt019x=     [HW,ALSA]

        snd-dummy=      [HW,ALSA]

        snd-emu10k1=    [HW,ALSA]

        snd-ens1370=    [HW,ALSA]

        snd-ens1371=    [HW,ALSA]

        snd-es968=      [HW,ALSA]

        snd-es1688=     [HW,ALSA]

        snd-es18xx=     [HW,ALSA]

        snd-es1938=     [HW,ALSA]

        snd-es1968=     [HW,ALSA]

        snd-fm801=      [HW,ALSA]

        snd-gusclassic= [HW,ALSA]

        snd-gusextreme= [HW,ALSA]

        snd-gusmax=     [HW,ALSA]

        snd-hdsp=       [HW,ALSA]

        snd-ice1712=    [HW,ALSA]

        snd-intel8x0=   [HW,ALSA]

        snd-interwave=  [HW,ALSA]

        snd-interwave-stb=
                        [HW,ALSA]

        snd-korg1212=   [HW,ALSA]

        snd-maestro3=   [HW,ALSA]

        snd-mpu401=     [HW,ALSA]

        snd-mtpav=      [HW,ALSA]

        snd-nm256=      [HW,ALSA]

        snd-opl3sa2=    [HW,ALSA]

        snd-opti92x-ad1848=
                        [HW,ALSA]

        snd-opti92x-cs4231=
                        [HW,ALSA]

        snd-opti93x=    [HW,ALSA]

        snd-pmac=       [HW,ALSA]

        snd-rme32=      [HW,ALSA]

        snd-rme96=      [HW,ALSA]

        snd-rme9652=    [HW,ALSA]

        snd-sb8=        [HW,ALSA]

        snd-sb16=       [HW,ALSA]

        snd-sbawe=      [HW,ALSA]

        snd-serial=     [HW,ALSA]

        snd-sgalaxy=    [HW,ALSA]

        snd-sonicvibes= [HW,ALSA]

        snd-sun-amd7930=
                        [HW,ALSA]

        snd-sun-cs4231= [HW,ALSA]

        snd-trident=    [HW,ALSA]

        snd-usb-audio=  [HW,ALSA,USB]

        snd-via82xx=    [HW,ALSA]

        snd-virmidi=    [HW,ALSA]

        snd-wavefront=  [HW,ALSA]

        snd-ymfpci=     [HW,ALSA]

        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
                        See Documentation/sonypi.txt

        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
                        See Documentation/specialix.txt.

        spia_io_base=   [HW,MTD]
        spia_fio_base=
        spia_pedr=
        spia_peddr=

        sscape=         [HW,OSS]
                        Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>

        st=             [HW,SCSI] SCSI tape parameters (buffers, etc.)
                        See Documentation/scsi/st.txt.

        sti=            [PARISC,HW]
                        Format: <num>
                        Set the STI (builtin display/keyboard on the HP-PARISC
                        machines) console (graphic card) which should be used
                        as the initial boot-console.
                        See also comment in drivers/video/console/sticore.c.

        sti_font=       [HW]
                        See comment in drivers/video/console/sticore.c.

        stifb=          [HW]
                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]

        sunrpc.pool_mode=
                        [NFS]
                        Control how the NFS server code allocates CPUs to
                        service thread pools.  Depending on how many NICs
                        you have and where their interrupts are bound, this
                        option will affect which CPUs will do NFS serving.
                        Note: this parameter cannot be changed while the
                        NFS server is running.

                        auto        the server chooses an appropriate mode
                                    automatically using heuristics
                        global      a single global pool contains all CPUs
                        percpu      one pool for each CPU
                        pernode     one pool for each NUMA node (equivalent
                                    to global on non-NUMA machines)

        swiotlb=        [IA-64] Number of I/O TLB slabs

        switches=       [HW,M68k]

        sym53c416=      [HW,SCSI]
                        See header of drivers/scsi/sym53c416.c.

        sysrq_always_enabled
                        [KNL]
                        Ignore sysrq setting - this boot parameter will
                        neutralize any effect of /proc/sys/kernel/sysrq.
                        Useful for debugging.

        t128=           [HW,SCSI]
                        See header of drivers/scsi/t128.c.

        tdfx=           [HW,DRM]

        thash_entries=  [KNL,NET]
                        Set number of hash buckets for TCP connection

        thermal.act=    [HW,ACPI]
                        -1: disable all active trip points in all thermal zones
                        <degrees C>: override all lowest active trip points

        thermal.crt=    [HW,ACPI]
                        -1: disable all critical trip points in all thermal zones
                        <degrees C>: lower all critical trip points

        thermal.nocrt=  [HW,ACPI]
                        Set to disable actions on ACPI thermal zone
                        critical and hot trip points.

        thermal.off=    [HW,ACPI]
                        1: disable ACPI thermal control

        thermal.psv=    [HW,ACPI]
                        -1: disable all passive trip points
                        <degrees C>: override all passive trip points to this value

        thermal.tzp=    [HW,ACPI]
                        Specify global default ACPI thermal zone polling rate
                        <deci-seconds>: poll all this frequency
                        0: no polling (default)

        tipar.timeout=  [HW,PPT]
                        Set communications timeout in tenths of a second
                        (default 15).

        tipar.delay=    [HW,PPT]
                        Set inter-bit delay in microseconds (default 10).

        tmscsim=        [HW,SCSI]
                        See comment before function dc390_setup() in
                        drivers/scsi/tmscsim.c.

        tp720=          [HW,PS2]

        trix=           [HW,OSS] MediaTrix AudioTrix Pro
                        Format:
                        <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>

        turbografx.map[2|3]=    [HW,JOY]
                        TurboGraFX parallel port interface
                        Format:
                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
                        See also Documentation/input/joystick-parport.txt

        u14-34f=        [HW,SCSI] UltraStor 14F/34F SCSI host adapter
                        See header of drivers/scsi/u14-34f.c.

        uart401=        [HW,OSS]
                        Format: <io>,<irq>

        uart6850=       [HW,OSS]
                        Format: <io>,<irq>

        uhci-hcd.ignore_oc=
                        [USB] Ignore overcurrent events (default N).
                        Some badly-designed motherboards generate lots of
                        bogus events, for ports that aren't wired to
                        anything.  Set this parameter to avoid log spamming.
                        Note that genuine overcurrent events won't be
                        reported either.

        usbcore.autosuspend=
                        [USB] The autosuspend time delay (in seconds) used
                        for newly-detected USB devices (default 2).  This
                        is the time required before an idle device will be
                        autosuspended.  Devices for which the delay is set
                        to a negative value won't be autosuspended at all.

        usbhid.mousepoll=
                        [USBHID] The interval which mice are to be polled at.

        vdso=           [X86-32,SH,x86-64]
                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
                        vdso=1: enable VDSO (default)
                        vdso=0: disable VDSO mapping

        vdso32=         [X86-32,X86-64]
                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
                        vdso32=1: enable 32-bit VDSO (default)
                        vdso32=0: disable 32-bit VDSO mapping

        vector=         [IA-64,SMP]
                        vector=percpu: enable percpu vector domain

        video=          [FB] Frame buffer configuration
                        See Documentation/fb/modedb.txt.

        vga=            [BOOT,X86-32] Select a particular video mode
                        See Documentation/i386/boot.txt and
                        Documentation/svga.txt.
                        Use vga=ask for menu.
                        This is actually a boot loader parameter; the value is
                        passed to the kernel using a special protocol.

        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
                        size of <nn>. This can be used to increase the
                        minimum size (128MB on x86). It can also be used to
                        decrease the size and leave more room for directly
                        mapped kernel RAM.

        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
                        Format: <command>

        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
                        Format: <command>

        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
                        Format: <command>

        waveartist=     [HW,OSS]
                        Format: <io>,<irq>,<dma>,<dma2>

        wd33c93=        [HW,SCSI]
                        See header of drivers/scsi/wd33c93.c.

        wd7000=         [HW,SCSI]
                        See header of drivers/scsi/wd7000.c.

        wdt=            [WDT] Watchdog
                        See Documentation/watchdog/wdt.txt.

        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
        xd_geo=         See header of drivers/block/xd.c.

        xirc2ps_cs=     [NET,PCMCIA]
                        Format:
                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]

        norandmaps      Don't use address space randomization
                        Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space

______________________________________________________________________

TODO:

        Add documentation for ALSA options.
        Add more DRM drivers.