Refactor quantum/split_common/i2c.c, quantum/split_common/serial.c (#4522)

* add temporary compile test shell script

* Extended support of SKIP_VERSION to make invariant compile results during testing.

* build_keyboard.mk, tmk_core/rules.mk: add LIB_SRC, QUANTUM_LIB_SRC support

Support compiled object enclosed in library.

e.g.
```
LIB_SRC += xxxx.c
xxxx.c --> xxxx.o ---> xxxx.a
```

* remove 'ifdef/ifndef USE_I2C' from quantum/split_common/{i2c|serial}.c

* add SKIP_DEBUG_INFO into tmk_core/rules.mk

When SKIP_DEBUG_INFO=yes is specified, do not use the -g option at compile time.

* tmk_core/rules.mk: Library object need -fno-lto

* add SKIP_DEBUG_INFO=yes

* remove temporary compile test shell script

* add '#define SOFT_SERIAL_PIN D0' to keyboards/lets_split/rev?/config.h

* quantum/split_common/serial.c: Changed not to use USE_I2C.

9 files changed, 56 insertions, 24 deletions

diff --git a/build_keyboard.mk b/build_keyboard.mk
index d225fe821..b639b92d3 100644
--- a/build_keyboard.mk
+++ b/build_keyboard.mk
@@ -34,6 +34,10 @@ $(error MASTER does not have a valid value(left/right))
     endif
 endif
 
+ifdef SKIP_VERSION
+    OPT_DEFS += -DSKIP_VERSION
+endif
+
 # Determine which subfolders exist.
 KEYBOARD_FOLDER_PATH_1 := $(KEYBOARD)
 KEYBOARD_FOLDER_PATH_2 := $(patsubst %/,%,$(dir $(KEYBOARD_FOLDER_PATH_1)))
@@ -278,6 +282,7 @@ ifneq ("$(wildcard $(KEYMAP_PATH)/config.h)","")
 endif
 
 # # project specific files
+SRC += $(patsubst %.c,%.clib,$(LIB_SRC))
 SRC += $(KEYBOARD_SRC) \
     $(KEYMAP_C) \
     $(QUANTUM_SRC)
@@ -296,6 +301,7 @@ include $(TMK_PATH)/protocol.mk
 include $(TMK_PATH)/common.mk
 include bootloader.mk
 
+SRC += $(patsubst %.c,%.clib,$(QUANTUM_LIB_SRC))
 SRC += $(TMK_COMMON_SRC)
 OPT_DEFS += $(TMK_COMMON_DEFS)
 EXTRALDFLAGS += $(TMK_COMMON_LDFLAGS)
diff --git a/common_features.mk b/common_features.mk
index 97febe2e7..73aab5d84 100644
--- a/common_features.mk
+++ b/common_features.mk
@@ -270,7 +270,7 @@ ifeq ($(strip $(SPLIT_KEYBOARD)), yes)
     endif
     OPT_DEFS += -DSPLIT_KEYBOARD
     QUANTUM_SRC += $(QUANTUM_DIR)/split_common/split_flags.c \
-                $(QUANTUM_DIR)/split_common/split_util.c \
-                $(QUANTUM_DIR)/split_common/i2c.c \
-                $(QUANTUM_DIR)/split_common/serial.c
+                $(QUANTUM_DIR)/split_common/split_util.c
+    QUANTUM_LIB_SRC += $(QUANTUM_DIR)/split_common/i2c.c
+    QUANTUM_LIB_SRC += $(QUANTUM_DIR)/split_common/serial.c
 endif
diff --git a/keyboards/lets_split/rev1/config.h b/keyboards/lets_split/rev1/config.h
index a8d614915..18b7cce5a 100644
--- a/keyboards/lets_split/rev1/config.h
+++ b/keyboards/lets_split/rev1/config.h
@@ -45,6 +45,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 /* Set 0 if debouncing isn't needed */
 #define DEBOUNCING_DELAY 5
 
+/* serial.c configuration for split keyboard */
+#define SOFT_SERIAL_PIN D0
+
 /* Mechanical locking support. Use KC_LCAP, KC_LNUM or KC_LSCR instead in keymap */
 #define LOCKING_SUPPORT_ENABLE
 /* Locking resynchronize hack */
diff --git a/keyboards/lets_split/rev2/config.h b/keyboards/lets_split/rev2/config.h
index 8844e5bb8..1c0871cd1 100644
--- a/keyboards/lets_split/rev2/config.h
+++ b/keyboards/lets_split/rev2/config.h
@@ -45,6 +45,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 /* Set 0 if debouncing isn't needed */
 #define DEBOUNCING_DELAY 5
 
+/* serial.c configuration for split keyboard */
+#define SOFT_SERIAL_PIN D0
+
 /* Mechanical locking support. Use KC_LCAP, KC_LNUM or KC_LSCR instead in keymap */
 #define LOCKING_SUPPORT_ENABLE
 /* Locking resynchronize hack */
diff --git a/keyboards/lets_split/sockets/config.h b/keyboards/lets_split/sockets/config.h
index 10d0c997e..6939d37dc 100644
--- a/keyboards/lets_split/sockets/config.h
+++ b/keyboards/lets_split/sockets/config.h
@@ -45,6 +45,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 /* Set 0 if debouncing isn't needed */
 #define DEBOUNCING_DELAY 5
 
+/* serial.c configuration for split keyboard */
+#define SOFT_SERIAL_PIN D0
+
 /* Mechanical locking support. Use KC_LCAP, KC_LNUM or KC_LSCR instead in keymap */
 #define LOCKING_SUPPORT_ENABLE
 /* Locking resynchronize hack */
diff --git a/quantum/split_common/i2c.c b/quantum/split_common/i2c.c
index b3d7fcc68..45e958b39 100644
--- a/quantum/split_common/i2c.c
+++ b/quantum/split_common/i2c.c
@@ -7,8 +7,6 @@
 #include "i2c.h"
 #include "split_flags.h"
 
-#if defined(USE_I2C) || defined(EH)
-
 // Limits the amount of we wait for any one i2c transaction.
 // Since were running SCL line 100kHz (=> 10μs/bit), and each transactions is
 // 9 bits, a single transaction will take around 90μs to complete.
@@ -184,4 +182,3 @@ ISR(TWI_vect) {
   // Reset everything, so we are ready for the next TWI interrupt
   TWCR |= (1<<TWIE) | (1<<TWINT) | (ack<<TWEA) | (1<<TWEN);
 }
-#endif
diff --git a/quantum/split_common/serial.c b/quantum/split_common/serial.c
index f34f824d7..13e58d825 100644
--- a/quantum/split_common/serial.c
+++ b/quantum/split_common/serial.c
@@ -12,18 +12,14 @@
 #include <stdbool.h>
 #include "serial.h"
 
-#ifndef USE_I2C
-
-#ifndef SOFT_SERIAL_PIN
-  #error quantum/split_common/serial.c need SOFT_SERIAL_PIN define
-#endif
+#ifdef SOFT_SERIAL_PIN
 
 #ifdef __AVR_ATmega32U4__
   // if using ATmega32U4 I2C, can not use PD0 and PD1 in soft serial.
-  #ifdef USE_I2C
-    #if SOFT_SERIAL_PIN == D0 || SOFT_SERIAL_PIN == D1
-      #error Using ATmega32U4 I2C, so can not use PD0, PD1
-    #endif
+  #ifdef USE_AVR_I2C
+     #if SOFT_SERIAL_PIN == D0 || SOFT_SERIAL_PIN == D1
+       #error Using ATmega32U4 I2C, so can not use PD0, PD1
+     #endif
   #endif
 
   #if SOFT_SERIAL_PIN >= D0 && SOFT_SERIAL_PIN <= D3
@@ -278,4 +274,4 @@ int serial_update_buffers(void) {
   return 0;
 }
 
-#endif
+#endif /* SOFT_SERIAL_PIN */
diff --git a/tmk_core/common/command.c b/tmk_core/common/command.c
index f79d5a257..aab99290d 100644
--- a/tmk_core/common/command.c
+++ b/tmk_core/common/command.c
@@ -181,7 +181,11 @@ static void print_version(void)
     print("VID: " STR(VENDOR_ID) "(" STR(MANUFACTURER) ") "
           "PID: " STR(PRODUCT_ID) "(" STR(PRODUCT) ") "
           "VER: " STR(DEVICE_VER) "\n");
+#ifdef SKIP_VERSION
+    print("BUILD:  (" __DATE__ ")\n");
+#else
     print("BUILD: " STR(QMK_VERSION) " (" __TIME__ " " __DATE__ ")\n");
+#endif
 
     /* build options */
     print("OPTIONS:"
diff --git a/tmk_core/rules.mk b/tmk_core/rules.mk
index ce3cd83b3..2e419dd66 100644
--- a/tmk_core/rules.mk
+++ b/tmk_core/rules.mk
@@ -28,12 +28,13 @@ VPATH :=
 
 # Convert all SRC to OBJ
 define OBJ_FROM_SRC
-$(patsubst %.c,$1/%.o,$(patsubst %.cpp,$1/%.o,$(patsubst %.cc,$1/%.o,$(patsubst %.S,$1/%.o,$($1_SRC)))))
+$(patsubst %.c,$1/%.o,$(patsubst %.cpp,$1/%.o,$(patsubst %.cc,$1/%.o,$(patsubst %.S,$1/%.o,$(patsubst %.clib,$1/%.a,$($1_SRC))))))
 endef
 $(foreach OUTPUT,$(OUTPUTS),$(eval $(OUTPUT)_OBJ +=$(call OBJ_FROM_SRC,$(OUTPUT))))
 
 # Define a list of all objects
 OBJ := $(foreach OUTPUT,$(OUTPUTS),$($(OUTPUT)_OBJ))
+NO_LTO_OBJ := $(filter %.a,$(OBJ))
 
 MASTER_OUTPUT := $(firstword $(OUTPUTS))
 
@@ -81,7 +82,9 @@ CSTANDARD = -std=gnu99
 #  -Wall...:     warning level
 #  -Wa,...:      tell GCC to pass this to the assembler.
 #    -adhlns...: create assembler listing
-CFLAGS += -g$(DEBUG)
+ifndef SKIP_DEBUG_INFO
+  CFLAGS += -g$(DEBUG)
+endif
 CFLAGS += $(CDEFS)
 CFLAGS += -O$(OPT)
 # add color
@@ -110,7 +113,9 @@ CFLAGS += $(CSTANDARD)
 #  -Wall...:     warning level
 #  -Wa,...:      tell GCC to pass this to the assembler.
 #    -adhlns...: create assembler listing
-CPPFLAGS += -g$(DEBUG)
+ifndef SKIP_DEBUG_INFO
+  CPPFLAGS += -g$(DEBUG)
+endif
 CPPFLAGS += $(CPPDEFS)
 CPPFLAGS += -O$(OPT)
 # to supress "warning: only initialized variables can be placed into program memory area"
@@ -138,7 +143,11 @@ CPPFLAGS += -Wa,-adhlns=$(@:%.o=%.lst)
 #  -listing-cont-lines: Sets the maximum number of continuation lines of hex
 #       dump that will be displayed for a given single line of source input.
 ASFLAGS += $(ADEFS) 
-ASFLAGS += -Wa,-adhlns=$(@:%.o=%.lst),-gstabs,--listing-cont-lines=100
+ifndef SKIP_DEBUG_INFO
+  ASFLAGS += -Wa,-adhlns=$(@:%.o=%.lst),-gstabs,--listing-cont-lines=100
+else
+  ASFLAGS += -Wa,-adhlns=$(@:%.o=%.lst),--listing-cont-lines=100
+endif
 
 #---------------- Library Options ----------------
 # Minimalistic printf version
@@ -210,6 +219,11 @@ ALL_CFLAGS = $(MCUFLAGS) $(CFLAGS) $(EXTRAFLAGS)
 ALL_CPPFLAGS = $(MCUFLAGS) -x c++ $(CPPFLAGS) $(EXTRAFLAGS)
 ALL_ASFLAGS = $(MCUFLAGS) -x assembler-with-cpp $(ASFLAGS) $(EXTRAFLAGS)
 
+define NO_LTO
+$(patsubst %.a,%.o,$1): NOLTO_CFLAGS += -fno-lto
+endef
+$(foreach LOBJ, $(NO_LTO_OBJ), $(eval $(call NO_LTO,$(LOBJ))))
+
 MOVE_DEP = mv -f $(patsubst %.o,%.td,$@) $(patsubst %.o,%.d,$@)
 
 
@@ -290,8 +304,8 @@ $1_INCFLAGS := $$(patsubst %,-I%,$$($1_INC))
 ifdef $1_CONFIG
 $1_CONFIG_FLAGS += $$(patsubst %,-include %,$$($1_CONFIG))
 endif
-$1_CFLAGS = $$(ALL_CFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS)
-$1_CPPFLAGS= $$(ALL_CPPFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS)
+$1_CFLAGS = $$(ALL_CFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS) $$(NOLTO_CFLAGS)
+$1_CPPFLAGS= $$(ALL_CPPFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS) $$(NOLTO_CFLAGS)
 $1_ASFLAGS= $$(ALL_ASFLAGS) $$($1_DEFS) $$($1_INCFLAGS) $$($1_CONFIG_FLAGS)
 
 # Compile: create object files from C source files.
@@ -321,6 +335,12 @@ $1/%.o : %.S $1/asflags.txt $1/compiler.txt | $(BEGIN)
 	$$(eval CMD=$$(CC) -c $$($1_ASFLAGS) $$< -o $$@)
 	@$$(BUILD_CMD)
 
+$1/%.a : $1/%.o
+	@mkdir -p $$(@D)
+	@$(SILENT) || printf "Archiving: $$<" | $$(AWK_CMD)
+	$$(eval CMD=$$(AR) $$@ $$<)
+	@$$(BUILD_CMD)
+
 $1/force:
 
 $1/cflags.txt: $1/force
@@ -346,7 +366,7 @@ $(MASTER_OUTPUT)/ldflags.txt: $(MASTER_OUTPUT)/force
 
 
 # We have to use static rules for the .d files for some reason
-DEPS = $(patsubst %.o,%.d,$(OBJ))
+DEPS = $(patsubst %.o,%.d,$(patsubst %.a,%.o,$(OBJ)))
 # Keep the .d files
 .PRECIOUS: $(DEPS)
 # Empty rule to force recompilation if the .d file is missing
@@ -391,7 +411,7 @@ $(shell mkdir -p $(BUILD_DIR) 2>/dev/null)
 $(eval $(foreach OUTPUT,$(OUTPUTS),$(shell mkdir -p $(OUTPUT) 2>/dev/null)))
 
 # Include the dependency files.
--include $(patsubst %.o,%.d,$(OBJ))
+-include $(patsubst %.o,%.d,$(patsubst %.a,%.o,$(OBJ)))
 
 
 # Listing of phony targets.