[PATCH master v1 2/6] firmware: turn missing firmware into linker error

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Appending to firmware-y results in an assembly file being generated that
defines a section embedding the firmware in question verbatim via .incbin.
To update the assembly file as required, the target has a dependency on
the firmware. When the firmware is missing, the build will abort there.

In preparation for deferring missing PBL firmware errors till the very
end, let's remove the firmware dependency if the missing firmware file
is built into PBL and replace the .incbin with a reference to an ultimately
undefined variable.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 firmware/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/firmware/Makefile b/firmware/Makefile
index 8050d0418d33..c66d19c677e8 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -41,6 +41,7 @@ obj-pbl-y := $(addsuffix .gen.o, $(firmware-y))
 
 FWNAME    = $(patsubst $(obj)/%.extgen.S,%,$(patsubst $(obj)/%.gen.S,%,$@))
 FWSTR     = $(subst /,_,$(subst .,_,$(subst -,_,$(FWNAME))))
+FWNAME_EXISTS = $(if $(wildcard $(fwdir)/$(FWNAME)),1,0)
 
 filechk_fwbin = { \
 	echo "/* Generated by $(src)/Makefile */"		;\
@@ -50,7 +51,11 @@ filechk_fwbin = { \
 	echo "    .p2align $(ASM_LGPTR)"			;\
 	echo ".global _fw_$(FWSTR)_start"			;\
 	echo "_fw_$(FWSTR)_start:"				;\
+	echo "\#if $(FWNAME_EXISTS)"				;\
 	echo "    .incbin \"$(fwdir)/$(FWNAME)\""		;\
+	echo "\#else"						;\
+	echo "ASM_PTR _fwname_$(FWSTR)"				;\
+	echo "\#endif"						;\
 	echo ".global _fw_$(FWSTR)_end"				;\
 	echo "_fw_$(FWSTR)_end:"				;\
 }
@@ -88,7 +93,7 @@ clean-files += *.sha.bin *.sum
 $(patsubst %.gen.o,$(obj)/%.gen.o, $(obj-pbl-y)): $(obj)/%.gen.o: $(fwdir)/%
 
 # The same for pbl:
-$(patsubst %.gen.o,$(obj)/%.gen.pbl.o, $(obj-pbl-y)): $(obj)/%.gen.pbl.o: $(fwdir)/%
+$(patsubst %.gen.o,$(obj)/%.gen.pbl.o, $(obj-pbl-y)): $(obj)/%.gen.pbl.o: $(wildcard $(fwdir)/%)
 $(patsubst %.gen.o,$(obj)/%.extgen.pbl.o, $(pbl-y)): $(obj)/%.extgen.pbl.o: $(fwdir)/%
 
 pbl-y := $(addsuffix .extgen.o, $(fw-external-y))
-- 
2.39.2