#+title: Linux kernel options
#+date: "2021-06-18 15:34:19 +08:00"
#+date_modified: "2021-06-18 15:34:48 +08:00"
#+language: en


- [[https://wiki.gentoo.org/wiki/Kernel][Gentoo wiki page on kernels]]
- Linux also has official documentation on kernel.org and tldp.org
- the kernel is large today, most of which can be configured to be compiled or not;
  there is a default configuration when compiling the kernel
- most of the features you would expect can be included
  + run ELF binaries
  + various filesystem support
  + virtualization support
  + Android drivers
  + debugging options for kernel hacking
  + pseudo-filesystems
  + most drivers for common hardware (e.g., LED, USB, and network devices)
  + special hardware drivers (e.g., Steam controller, Nintendo Wii)
- most of the options can be configured either to be included inside of the kernel image or as an external module
- most of the features are available as kernel options
  + =CONFIG_HID_GENERIC= enables support for generic devices such as mice, keyboards, joysticks
  + you can know what compile options is included from the kernel with =/proc/config.gz= but only if =CONFIG_IKCONFIG_PROC= is included
  + =CONFIG_HID_BATTERY_STRENGTH= enables reporting battery strength
- you can know what kernel options of the compiled kernel by looking at =/proc/config.gz= (e.g., ~gunzip --stdout /proc/config.gz | bat~);
  though, it is only possible if compiled with =CONFIG_IKCONFIG_PROC= option.
