[PATCH 1/3 V2] time: move timeconst.h into include/generated

[Nicholas Mc Guire]

kernel/time/timeconst.h is moved to include/generated/ and generated in
an early build stage by top level Kbuild. This allows using timeconst.h
in an earlier stage of the build.

Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
---

Thanks to Joe Perches <joe@xxxxxxxxxxx> for suggesting this approach and
catching the unconditional rebuild (should be fixed here now properly) as
well as for his review comments on the first attempts as well as for the
macro version that the reformatting of V2 re-uses.

V2: no changes in this one from V1

Some questions that remain:
 * Kbuild - is passing in arguments to .bc files via pipe and read();
   rather than using multiple files acceptable or is there some reason
   for the original multi-file solution that Im overlooking ?
 * conditional rebuild of timeconst.h with $(call filechk,gentimeconst)
   not really clear if this is going to do all rebuilds that could be
   necessary and not clear how to verify this. currently only checked by
   1) defconfig -> build -> rebuild -> CHK is executed timeconst.h unmodified
   2) defconfig -> build -> change HZ -> rebuild -> UPD timeconst.h resulting
      in a rebuild of most files.

Patch was compile tested for x86_64_defconfig,multi_v7_defconfig,
ppc64_defconfig, and boot/run
tested on x86_64. Further a test-case with an invalid HZ value to trigger the
error output in kernel/time/timeconst.bc was run.

Patch is against 4.0-rc7 (localversion-next is -next-20150410)

 Kbuild                   |   30 +++++++++++++++++++++++++-----
 kernel/time/Makefile     |   17 +----------------
 kernel/time/time.c       |    2 +-
 kernel/time/timeconst.bc |    3 ++-
 4 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/Kbuild b/Kbuild
index 6f0d82a..1d1aef5 100644
--- a/Kbuild
+++ b/Kbuild
@@ -2,8 +2,9 @@
 # Kbuild for top-level directory of the kernel
 # This file takes care of the following:
 # 1) Generate bounds.h
-# 2) Generate asm-offsets.h (may need bounds.h)
-# 3) Check for missing system calls
+# 2) Generate timeconst.h
+# 3) Generate asm-offsets.h (may need bounds.h)
+# 4) Check for missing system calls
 
 # Default sed regexp - multiline due to syntax constraints
 define sed-y
@@ -47,7 +48,26 @@ $(obj)/$(bounds-file): kernel/bounds.s FORCE
 	$(call filechk,offsets,__LINUX_BOUNDS_H__)
 
 #####
-# 2) Generate asm-offsets.h
+# 2) Generate timeconst.h
+
+timeconst-file := include/generated/timeconst.h
+
+always  += $(timeconst-file)
+targets += $(timeconst-file)
+
+quiet_cmd_gentimeconst = GEN     $@
+define cmd_gentimeconst
+	(echo $(CONFIG_HZ) | bc -q $< ) > $@
+endef
+define filechk_gentimeconst
+	(echo $(CONFIG_HZ) | bc -q $< )
+endef
+
+$(obj)/$(timeconst-file): kernel/time/timeconst.bc FORCE
+	$(call filechk,gentimeconst)
+
+#####
+# 3) Generate asm-offsets.h
 #
 
 offsets-file := include/generated/asm-offsets.h
@@ -65,7 +85,7 @@ $(obj)/$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
 	$(call filechk,offsets,__ASM_OFFSETS_H__)
 
 #####
-# 3) Check for missing system calls
+# 4) Check for missing system calls
 #
 
 always += missing-syscalls
@@ -78,4 +98,4 @@ missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
 	$(call cmd,syscalls)
 
 # Keep these two files during make clean
-no-clean-files := $(bounds-file) $(offsets-file)
+no-clean-files := $(bounds-file) $(offsets-file) $(timeconst-file)
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index 01f0312..ffc4cc3 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -13,19 +13,4 @@ obj-$(CONFIG_TIMER_STATS)			+= timer_stats.o
 obj-$(CONFIG_DEBUG_FS)				+= timekeeping_debug.o
 obj-$(CONFIG_TEST_UDELAY)			+= test_udelay.o
 
-$(obj)/time.o: $(obj)/timeconst.h
-
-quiet_cmd_hzfile = HZFILE  $@
-      cmd_hzfile = echo "hz=$(CONFIG_HZ)" > $@
-
-targets += hz.bc
-$(obj)/hz.bc: $(objtree)/include/config/hz.h FORCE
-	$(call if_changed,hzfile)
-
-quiet_cmd_bc  = BC      $@
-      cmd_bc  = bc -q $(filter-out FORCE,$^) > $@
-
-targets += timeconst.h
-$(obj)/timeconst.h: $(obj)/hz.bc $(src)/timeconst.bc FORCE
-	$(call if_changed,bc)
-
+$(obj)/time.o: $(objtree)/include/config/
diff --git a/kernel/time/time.c b/kernel/time/time.c
index 2c85b77..4fa1d26 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -41,7 +41,7 @@
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 
-#include "timeconst.h"
+#include <generated/timeconst.h>
 #include "timekeeping.h"
 
 /*
diff --git a/kernel/time/timeconst.bc b/kernel/time/timeconst.bc
index 511bdf2..c7388de 100644
--- a/kernel/time/timeconst.bc
+++ b/kernel/time/timeconst.bc
@@ -50,7 +50,7 @@ define timeconst(hz) {
 	print "#include <linux/types.h>\n\n"
 
 	print "#if HZ != ", hz, "\n"
-	print "#error \qkernel/timeconst.h has the wrong HZ value!\q\n"
+	print "#error \qinclude/generated/timeconst.h has the wrong HZ value!\q\n"
 	print "#endif\n\n"
 
 	if (hz < 2) {
@@ -105,4 +105,5 @@ define timeconst(hz) {
 	halt
 }
 
+hz = read();
 timeconst(hz)
-- 
1.7.10.4

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