Config brainstorming
====================

Brainstorming for enable Kconfig on compat-drivers

Step 1
------

Using the existing kernel's config, generate a Kconfig file that
contains all the right symbols for that kernel::

   cat .config | genkconf.sh > kernel-kconfig

where the script is this:

.. code-block:: bash

   #!/bin/bash

   while read line ; do
       case "${line:0:7}" in
       "CONFIG_")
           line="${line:7}"
           cfg="${line%%=*}"
           val="${line#*=}"
           cfgtype="skip"
           if [ "$val" = "m" ] ; then
               cfgtype="tristate"
           elif [ "$val" = "y" ] ; then
               cfgtype="bool"
           fi
           if [ "$cfgtype" != "skip" ] ; then
               echo "config $cfg"
               echo "    $cfgtype"
               echo "    default $val"
               echo ""
           fi
           ;;
       "# CONFI")
           cfg="${line:9}"
           cfg="${cfg%% is not set}"
           echo "config $cfg"
           echo "    bool"
           echo "    default n"
           echo ""
           ;;
       esac
   done

Step 2
------

Collect all Kconfig symbols from compat::

   find . -name Kconfig | xargs cat | sed 's/^config //;t;d' > symbols

Step 3
------

Instead of patching Makefiles, replaces all CONFIG\_ by CONFIG_COMPAT\_
in all Makefiles::

   find . -name Makefile | xargs rpl "CONFIG_" "CONFIG_COMPAT_"

This means that only things that are actually selected in compat will be built.

Step 4
------

Replace all "FOO" with "COMPAT_FOO" symbols in Kconfig and code files:

.. code-block:: bash

   for sym in $(cat symbols) ; do
       find . -name Kconfig |\
           xargs rpl -w "$sym" "COMPAT_$sym"

       find . -name '*.c' -o -name '*.h' |\
           xargs rpl -w "CONFIG_$sym" "CONFIG_COMPAT_$sym"
   done

Step 5
------

Build a Kconfig file::

   echo 'source "kernel-kconfig"' > Kconfig
   for k in drivers/net/wireless/*/Kconfig ; do echo "source \"$k\"" >> Kconfig ; done

etc. Currently, mac80211/cfg80211/... Kconfig isn't copied. They will
need to be copied and potentially modified for dependencies like WEXT.

Step 6
------

Run menuconfig::

   /lib/modules/$(uname -r)/build/scripts/kconfig/mconf Kconfig

Step 7
------

Build the thing.

The generated .config can be parsed with either the existing
compat-drivers/scripts/gen-compat-autoconf.sh script or
scripts/kconfig/confdata.c (conf --silentoldconfig). The generated
include/linux/compat_autoconf.h is already included as part of the build
of compat-drivers.