kernel – passing module parameters

With normal programs that allow you pass parameters on there command line, for example

printoutmyname genux

where the program is called printoutmyname and the first parameter is genux (it is normal that the first parameter [0] is actually the program name and the second parameter [1] is the parameter that is passed)

Well in Linux kernel (where here is a example on how to compile the kernel for a ubuntu based setup) you can pass parameters to the modules that are getting loaded. One module would be your graphics card, in my case a nvidia graphics card.

To find out what parameters can be passed to the graphics card you will have to find the kernel module file (filename.ko, where the ko is the kernel object file), so to search for the nvidia.ko in my case I did

locate nvidia.ko

and then changed to that directory and did a module information on it

cd /lib/modules/2.6.31-17-generic/updates/dkms/
ls
nvidia.ko  vboxdrv.ko  vboxnetadp.ko  vboxnetflt.ko

and doing a module information on it you call the modinfo on the kernel object file as

modinfo nvidia.ko
</pre
 
my output was
 
<pre lang="bash">
filename:       nvidia.ko
license:        NVIDIA
alias:          char-major-195-*
alias:          pci:v000010DEd*sv*sd*bc03sc02i00*
alias:          pci:v000010DEd*sv*sd*bc03sc00i00*
depends:
vermagic:       2.6.31-17-generic SMP mod_unload modversions
parm:           NVreg_EnableVia4x:int
parm:           NVreg_EnableALiAGP:int
parm:           NVreg_ReqAGPRate:int
parm:           NVreg_EnableAGPSBA:int
parm:           NVreg_EnableAGPFW:int
parm:           NVreg_Mobile:int
parm:           NVreg_ResmanDebugLevel:int
parm:           NVreg_RmLogonRC:int
parm:           NVreg_ModifyDeviceFiles:int
parm:           NVreg_DeviceFileUID:int
parm:           NVreg_DeviceFileGID:int
parm:           NVreg_DeviceFileMode:int
parm:           NVreg_RemapLimit:int
parm:           NVreg_UpdateMemoryTypes:int
parm:           NVreg_UseVBios:int
parm:           NVreg_RMEdgeIntrCheck:int
parm:           NVreg_UsePageAttributeTable:int
parm:           NVreg_EnableMSI:int
parm:           NVreg_MapRegistersEarly:int
parm:           NVreg_RmNvclkIdleGraphics:int
parm:           NVreg_RegistryDwords:charp
parm:           NVreg_NvAGP:int

where the parm: is a parameter to pass to the module on load (insmod, or loaded via the kernel at boot time which you can force to load via the /etc/modules file and the parameters can be placed in the /etc/modprobe.d directory).

for example to load the nvidia module with a parameter NVreg_NvAGP you would do something like

insmod nvidia.ko NVreg_NvAGP=1

and the passing value is 1 to the NVreg_NvAGP parameter

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