MIPS: generic: Allow filtering enabled boards by requirements

Up until now when configuring a generic kernel all board config
fragments have been merged by default unless boards are explicitly
selected by the user specifying BOARDS=.

In many cases this is sub-optimal, since some boards don't make sense to
include in some kernels. For example the MIPS SEAD-3 development board
has only ever been used with 32 bit CPUs, so including support for the
SEAD-3 in a 64 bit kernel is wasteful.

This patch introduces support for specifying requirements in board
config fragments, using comments formatted like so:

  # require CONFIG_BLA=y

For example the SEAD-3 board could specify that it should only be merged
for 32 bit kernels using a requirement line like the following:

  # require CONFIG_32BIT=y

A new generic-board-config.sh script is introduced to handle selecting
the board config fragments to merge & calling merge_config.sh to merge
them. In order to allow requirements to check Kconfig symbols that are
implicitly selected, rather than explicitly specified by
generic_defconfig or one of the ISA config fragments, an intermediate
.config file is saved & used as a reference when checking requirements.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16943/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/MAINTAINERS b/MAINTAINERS
index 31d4274efb06a4975ef10c1514fcce13154aaaf8..b526acd23ae1ece795e222021698650789db5337 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8792,6 +8792,7 @@ M:        Paul Burton <paul.burton@imgtec.com>
 L:     linux-mips@linux-mips.org
 S:     Supported
 F:     arch/mips/generic/
+F:     arch/mips/tools/generic-board-config.sh
 
 MIPS/LOONGSON1 ARCHITECTURE
 M:     Keguang Zhang <keguang.zhang@gmail.com>

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 38360f776b6f7470e67c9bf2d474a074e0124897..0e0aa64a9c881f7dbaa636ae565010b542ecd9cd 100644 (file)
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -500,8 +500,14 @@ $(eval $(call gen_generic_defconfigs,micro32,r2,eb el))
 .PHONY: $(generic_defconfigs)
 $(generic_defconfigs):
        $(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh \
-               -m -O $(objtree) $(srctree)/arch/$(ARCH)/configs/generic_defconfig $^ \
-               $(foreach board,$(BOARDS),$(generic_config_dir)/board-$(board).config)
+               -m -O $(objtree) $(srctree)/arch/$(ARCH)/configs/generic_defconfig $^ | \
+               grep -Ev '^#'
+       $(Q)cp $(KCONFIG_CONFIG) $(objtree)/.config.$@
+       $(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig \
+               KCONFIG_CONFIG=$(objtree)/.config.$@ >/dev/null
+       $(Q)$(CONFIG_SHELL) $(srctree)/arch/$(ARCH)/tools/generic-board-config.sh \
+               $(srctree) $(objtree) $(objtree)/.config.$@ $(KCONFIG_CONFIG) \
+               "$(origin BOARDS)" $(BOARDS)
        $(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
 
 #

diff --git a/arch/mips/tools/generic-board-config.sh b/arch/mips/tools/generic-board-config.sh
new file mode 100755 (executable)
index 0000000..5c4f936
--- /dev/null
+++ b/arch/mips/tools/generic-board-config.sh
@@ -0,0 +1,90 @@
+#!/bin/sh
+#
+# Copyright (C) 2017 Imagination Technologies
+# Author: Paul Burton <paul.burton@imgtec.com>
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation;  either version 2 of the  License, or (at your
+# option) any later version.
+#
+# This script merges configuration fragments for boards supported by the
+# generic MIPS kernel. It checks each for requirements specified using
+# formatted comments, and then calls merge_config.sh to merge those
+# fragments which have no unmet requirements.
+#
+# An example of requirements in your board config fragment might be:
+#
+# # require CONFIG_CPU_MIPS32_R2=y
+# # require CONFIG_CPU_LITTLE_ENDIAN=y
+#
+# This would mean that your board is only included in kernels which are
+# configured for little endian MIPS32r2 CPUs, and not for example in kernels
+# configured for 64 bit or big endian systems.
+#
+
+srctree="$1"
+objtree="$2"
+ref_cfg="$3"
+cfg="$4"
+boards_origin="$5"
+shift 5
+
+cd "${srctree}"
+
+# Only print Skipping... lines if the user explicitly specified BOARDS=. In the
+# general case it only serves to obscure the useful output about what actually
+# was included.
+case ${boards_origin} in
+"command line")
+       print_skipped=1
+       ;;
+environment*)
+       print_skipped=1
+       ;;
+*)
+       print_skipped=0
+       ;;
+esac
+
+for board in $@; do
+       board_cfg="arch/mips/configs/generic/board-${board}.config"
+       if [ ! -f "${board_cfg}" ]; then
+               echo "WARNING: Board config '${board_cfg}' not found"
+               continue
+       fi
+
+       # For each line beginning with # require, cut out the field following
+       # it & search for that in the reference config file. If the requirement
+       # is not found then the subshell will exit with code 1, and we'll
+       # continue on to the next board.
+       grep -E '^# require ' "${board_cfg}" | \
+           cut -d' ' -f 3- | \
+           while read req; do
+               case ${req} in
+               *=y)
+                       # If we require something =y then we check that a line
+                       # containing it is present in the reference config.
+                       grep -Eq "^${req}\$" "${ref_cfg}" && continue
+                       ;;
+               *=n)
+                       # If we require something =n then we just invert that
+                       # check, considering the requirement met if there isn't
+                       # a line containing the value =y in the reference
+                       # config.
+                       grep -Eq "^${req/%=n/=y}\$" "${ref_cfg}" || continue
+                       ;;
+               *)
+                       echo "WARNING: Unhandled requirement '${req}'"
+                       ;;
+               esac
+
+               [ ${print_skipped} -eq 1 ] && echo "Skipping ${board_cfg}"
+               exit 1
+       done || continue
+
+       # Merge this board config fragment into our final config file
+       ./scripts/kconfig/merge_config.sh \
+               -m -O ${objtree} ${cfg} ${board_cfg} \
+               | grep -Ev '^(#|Using)'
+done