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Update README.txt 

The config portion of README.txt hasn't reflected reality for a while
now. With the change of how configuration options are generated, it's
even less reflective of reality. Update it to be a bit more useful.
This commit is contained in:
Laura Abbott 2016-12-20 10:01:24 -08:00
parent df505fba5d
commit dd50066e0b
1 changed files with 24 additions and 28 deletions
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README.txt
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@ -31,30 +31,29 @@ by make verrel
config heirarchy.
-----------------
Instead of having to maintain a config file for every arch variant we build on,
the kernel spec uses a nested system of configs. At the top level, is
config-generic. Add options here that should be present in every possible
config on all architectures.
the kernel spec uses a nested system of configs. Each option CONFIG_FOO is
represented by a single file named CONFIG_FOO which contains the state (=y, =m,
=n). These options are collected in the folder baseconfig. Architecture specifi
options are set in nested folders. An option set in a nested folder will
override the same option set in one of the higher levels.
Beneath this are per-arch overrides. For example config-x86-generic add
additional x86 specific options, and also _override_ any options that were
set in config-generic.
The individual CONFIG_FOO files only exist in the pkg-git repository. The RPM
contains kernel-foo.config files which are the result of combining all the
CONFIG_FOO files. The files are combined by running build_configs.sh. This
script _must_ be run each time one of the options is changed.
The heirarchy looks like this..
Example flow:
config-generic
|
config-x86-generic
| |
config-x86-32-generic config-x86-64-generic
An option set in a lower level will override the same option set in one
of the higher levels.
There exist two additional overrides, config-debug, and config-nodebug,
which override -generic, and the per-arch overrides. It is documented
further below.
# Enable the option CONFIG_ABC123 as a module for all arches
echo "CONFIG_ABC123=m" > baseconfig/CONFIG_ABC1234
# enable the option CONFIG_XYZ321 for only x86
echo "# CONFIG_XYZ321 is not set" > baseconfig/CONFIG_XYZ321
echo "CONFIG_XYZ321=m" > baseconfig/x86/CONFIG_XYZ321
# regenerate the combined config files
./build_configs.sh
The file config_generation gives a listing of what folders go into each
config file generated.
debug options.
--------------
@ -69,14 +68,11 @@ typically been run already, which sets up the following..
If we are building for rawhide, 'make debug' has been run, which changes
the status quo to:
- We only build one kernel 'kernel'
- The debug options from 'config-debug' are always turned on.
- The debug options are always turned on.
This is done to increase coverage testing, as not many people actually
run kernel-debug.
To add new debug options, add an option to _both_ config-debug and config-nodebug,
and also new stanzas to the Makefile 'debug' and 'release' targets.
Sometimes debug options get added to config-generic, or per-arch overrides
instead of config-[no]debug. In this instance, the options should have no
discernable performance impact, otherwise they belong in the debug files.
The debug options are managed in a separate heierarchy under debugconfig. This
works in a similar manner to baseconfig. More deeply nested folders, again,
override options. The file config_generation gives a listing of what folders
go into each config file generated.