Kernel Modules

Posted on Thu 28 March 2019 in linux

Kernel options can be either built into the kernel, or stand-alone as modules.

1. Built-in

check existence ls /sys/module/<mod_name>
check parameter cat /sys/module/<mod_nam>/parameters/<param_name>
modify parameter set <mod_name>.<param_name>=<param_value> in kernel command line

1.1 Example: enable guc in i915

$ cat /sys/module/i915/parameters/enable_guc
  # current value = 0 (disabled)

$ grep enable_guc -A4 -m1 /usr/src/linux/drivers/gpu/drm/i915/i915_params.c
  i915_param_named_unsafe(enable_guc, int, 0400,
      "Enable GuC load for GuC submission and/or HuC load. "
      "Required functionality can be selected using bitmask values. "
      "(-1=auto, 0=disable [default], 1=GuC submission, 2=HuC load)");
  # set value -1 to enable

According to the above output, append i915.enable_guc=-1 to kernel command line.

If efibootmgr is the boot manager, just issue:

efibootmgr -c -d /dev/nvme0n1 -L 'gentoo' -u 'root=PARTUUID=817fae1c-8972-6318-531a-1b5a9821de23 i915.enable_guc=-1'

P.S. see more here

P.P.S. use unicode if the default ASCII codes are garbled in efibootmgr.

2. Stand-alone

check existence lsmod <mod_name> (usu. residing in /lib/modules/$(uname -r)/kernel)
load a module modprobe <mod_name>
check parameter modinfo -p <mod_name>
modify parameter option <mod_name> <param_name>=<param_value> in /etc/modprobe.d/<mod_name>.conf (sample)


note: check EXTRAVERSION in top level Makefile ; compile wanted module by specifying its directory name ; installation compression alternative: zstd