litex_sim: add GPIO module exposed through simctrl

Adds a GPIO controller module, which is exposed through
simctrl. Supports driving GPIO pins, as well as querying the current
pin state (input/output) and signal state. Exposes a JSON-based
interface through the simctrl payload.

Signed-off-by: Leon Schuermann <leon@is.currently.online>

litex/build/sim/core/modules/Makefile

@@ -1,5 +1,5 @@
 include ../variables.mak
-MODULES = simctrl xgmii_ethernet gmii_ethernet ethernet serial2console serial2tcp clocker spdeeprom
+MODULES = simctrl gpio xgmii_ethernet gmii_ethernet ethernet serial2console serial2tcp clocker spdeeprom
 
 .PHONY: $(MODULES)
 all: $(MODULES)

litex/build/sim/core/modules/gpio/Makefile

@@ -0,0 +1,14 @@
+include ../../variables.mak
+UNAME_S := $(shell uname -s)
+
+include $(SRC_DIR)/modules/rules.mak
+
+CFLAGS += -I$(TAPCFG_DIRECTORY)/src/include
+OBJS = $(MOD).o
+
+$(MOD).so: $(OBJS)
+ifeq ($(UNAME_S),Darwin)
+	$(CC) $(LDFLAGS) -o $@ $^
+else
+	$(CC) $(LDFLAGS) -Wl,-soname,$@ -o $@ $^
+endif