Linux kernel CONFIG symbols

CONFIG_DEBUG_INFO

Needed to compile the kernel with debug symbols.

CONFIG_DRM

Direct rendering manager.

CONFIG_DRM_I915

For Systems with Intel Grpahics Media Accelerator or HD Graphics.

CONFIG_FUSE_FS

CONFIG_FUSE_FS is apparently needed for the ntfs-3g kernel module because ntfs-3g runs in user space (and depends on fuse).

CONFIG_IKCONFIG_PROC

Required for /proc/config.gz

CONFIG_SND

Advanced Linux sound architecture

See also CONFIG_SOUND, CONFIG_SOUND_PRIME

CONFIG_SND_HDA_CODEC_REALTEK

I needed this to enable this driver for my sound card.

CONFIG_SOUND

Support for Linux sound cards, minimum setting for ALSA.

CONFIG_SOUND_PRIME

Deprecated.

CONFIG_INPUT_UINPUT

User level driver support, apparently needed for LFS: libevdev

TODO

Setting the config option OPT to m results in #define CONFIG_OPT_MODULE 1 in include/generated/autoconf.h.

The macros IS_BUILTIN, IS_MODULE, IS_ENABLED and IS_REACHABLE defined in include/linux/kconfig.h.

Some (interesting?) config options

`EFI_HANDOVER_PROTOCOL`	Support for the deprecated EFI handover protocol which defines alternative entry points into the EFI stub (which has not basis in the UEFI specification). Although the corresponding support is not present in upstream GRUB or other bootloaders, most distros build GRUB with downstream patches applied which rely on the handover protocol. See also `EFI_MIXED`.
`EFI_MIXED`	allows a 64-bit kernel to be booted on a 32-bit firmware (if CPU supported 64-bit mode). A mixed-mode enabled kernel cannot be booted via the EFI boot stub, though - a bootloader that supports the EFI handover protocol must be used. See also `EFI_HANDOVER_PROTOCOL`
`EFI_STUB`	allows `bzImage` to be loaded directly be EFI firmware without a bootloader. See `Documentation/admin-guide/efi-stub.rst`.
`EXPERT`
`FB`	Frame buffer device (see also `/dev/fbN`)
`HYPERV`	Hyper-V client drivers
`HZ`, `HZ_100` etc.	`include/asm-generic/param.h` defines `HZ` to the value of `CONFIG_HZ` and has the comment Internal kernel timer frequency. See also `kernel/Kconfig.hz`
`INPUT_EVDEV`	Required for input device events to be accessible in `/dev/input/eventX` (which seems to be necessary for X Server ?)
`PACKET`	The packet protocol allows applications (such as `tcpdump`) to communicate directly with network devices withou an intermediate network protocol. Apparently, `PACKET` needs to be enabled for `wpa_supplicant`.
`X86`, `X86_32`, `X86_64`, `64BIT`	What is the difference between `X86_64` and `64BIT`.

Modification of CONFIG symbols

As the Kernel is developed, CONFIG symbols are deleted, added or renamed with the potential consequence that make oldconfig won't necessarily produce a working Kernel anymore.

A list of new config symbols can be produced with

$ cp /path/to/old.config .config
$ make listnewconfig

The alternative brute force method is:

$ make oldconfig
$ scripts/diffconfig old.config .config