kbuild: change *FLAGS_<basetarget>.o to take the path relative to $(obj)

Kbuild provides per-file compiler flag addition/removal:

  CFLAGS_<basetarget>.o
  CFLAGS_REMOVE_<basetarget>.o
  AFLAGS_<basetarget>.o
  AFLAGS_REMOVE_<basetarget>.o
  CPPFLAGS_<basetarget>.lds
  HOSTCFLAGS_<basetarget>.o
  HOSTCXXFLAGS_<basetarget>.o

The <basetarget> is the filename of the target with its directory and
suffix stripped.

This syntax comes into a trouble when two files with the same basename
appear in one Makefile, for example:

  obj-y += foo.o
  obj-y += dir/foo.o
  CFLAGS_foo.o := <some-flags>

Here, the <some-flags> applies to both foo.o and dir/foo.o

The real world problem is:

  scripts/kconfig/util.c
  scripts/kconfig/lxdialog/util.c

Both files are compiled into scripts/kconfig/mconf, but only the
latter should be given with the ncurses flags.

It is more sensible to use the relative path to the Makefile, like this:

  obj-y += foo.o
  CFLAGS_foo.o := <some-flags>
  obj-y += dir/foo.o
  CFLAGS_dir/foo.o := <other-flags>

At first, I attempted to replace $(basetarget) with $*. The $* variable
is replaced with the stem ('%') part in a pattern rule. This works with
most of cases, but does not for explicit rules.

For example, arch/ia64/lib/Makefile reuses rule_as_o_S in its own
explicit rules, so $* will be empty, resulting in ignoring the per-file
AFLAGS.

I introduced a new variable, target-stem, which can be used also from
explicit rules.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Marc Zyngier <maz@kernel.org>

drivers/gpu/drm/amd/display/dc/calcs/Makefile

@@ -32,9 +32,9 @@ endif
 
 calcs_ccflags := -mhard-float -msse $(cc_stack_align)
 
-CFLAGS_dcn_calcs.o := $(calcs_ccflags)
-CFLAGS_dcn_calc_auto.o := $(calcs_ccflags)
-CFLAGS_dcn_calc_math.o := $(calcs_ccflags) -Wno-tautological-compare
+CFLAGS_$(AMDDALPATH)/dc/calcs/dcn_calcs.o := $(calcs_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/calcs/dcn_calc_auto.o := $(calcs_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/calcs/dcn_calc_math.o := $(calcs_ccflags) -Wno-tautological-compare
 
 BW_CALCS = dce_calcs.o bw_fixed.o custom_float.o
 

drivers/gpu/drm/amd/display/dc/dcn20/Makefile

@@ -16,7 +16,7 @@ else ifneq ($(call cc-option, -mstack-alignment=16),)
 	cc_stack_align := -mstack-alignment=16
 endif
 
-CFLAGS_dcn20_resource.o := -mhard-float -msse $(cc_stack_align)
+CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -mhard-float -msse $(cc_stack_align)
 
 AMD_DAL_DCN20 = $(addprefix $(AMDDALPATH)/dc/dcn20/,$(DCN20))
 

drivers/gpu/drm/amd/display/dc/dml/Makefile

@@ -32,19 +32,16 @@ endif
 
 dml_ccflags := -mhard-float -msse $(cc_stack_align)
 
-CFLAGS_display_mode_lib.o := $(dml_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dml/display_mode_lib.o := $(dml_ccflags)
 
 ifdef CONFIG_DRM_AMD_DC_DCN2_0
-CFLAGS_display_mode_vba.o := $(dml_ccflags)
-CFLAGS_display_mode_vba_20.o := $(dml_ccflags)
-CFLAGS_display_rq_dlg_calc_20.o := $(dml_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dml/display_mode_vba.o := $(dml_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dml/dcn20/display_mode_vba_20.o := $(dml_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dml/dcn20/display_rq_dlg_calc_20.o := $(dml_ccflags)
 endif
-ifdef CONFIG_DRM_AMD_DCN3AG
-CFLAGS_display_mode_vba_3ag.o := $(dml_ccflags)
-endif
-CFLAGS_dml1_display_rq_dlg_calc.o := $(dml_ccflags)
-CFLAGS_display_rq_dlg_helpers.o := $(dml_ccflags)
-CFLAGS_dml_common_defs.o := $(dml_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dml/dml1_display_rq_dlg_calc.o := $(dml_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dml/display_rq_dlg_helpers.o := $(dml_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dml/dml_common_defs.o := $(dml_ccflags)
 
 DML = display_mode_lib.o display_rq_dlg_helpers.o dml1_display_rq_dlg_calc.o \
 	dml_common_defs.o

drivers/gpu/drm/amd/display/dc/dsc/Makefile

@@ -9,10 +9,9 @@ endif
 
 dsc_ccflags := -mhard-float -msse $(cc_stack_align)
 
-CFLAGS_rc_calc.o := $(dsc_ccflags)
-CFLAGS_rc_calc_dpi.o := $(dsc_ccflags)
-CFLAGS_codec_main_amd.o := $(dsc_ccflags)
-CFLAGS_dc_dsc.o := $(dsc_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dsc/rc_calc.o := $(dsc_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dsc/rc_calc_dpi.o := $(dsc_ccflags)
+CFLAGS_$(AMDDALPATH)/dc/dsc/dc_dsc.o := $(dsc_ccflags)
 
 DSC = dc_dsc.o rc_calc.o rc_calc_dpi.o