feat: add discrete-input support and RPU config-writable check

drivers/rpu.py

@@ -1,10 +1,16 @@
 import time
 
 from common.config_loader import load_garuda_registers
-from drivers.modbus_device import ModbusDevice
+from drivers.modbus_device import ModbusDevice, ModbusDeviceError
 
 DEFAULT_DATASETS = ["Sec_normal", "sec_flash"]
 
+# SEC_STATE values that allow modbus_to_config()/write_all_flash() to run
+# (garuda-dsp/app/app_modbus/app_modbus.c update_modbus_input()).
+# SEC_RUN (charging) is NOT in this set - config writes are silently ignored
+# while charging is active.
+CONFIG_WRITABLE_STATES = {1, 9, 238, 240, 241}  # READY, PRE_READY, ERROR, DEBUG_READY, DEBUG_FREQ_CAL
+
 
 class Rpu(ModbusDevice):
     """Covers every register in Sec_normal + sec_flash by label via read()/write()
@@ -37,6 +43,14 @@ class Rpu(ModbusDevice):
     def read_shadow_error_code(self):
         return (self.read("Shadow_error_code_hi") << 16) | self.read("Shadow_error_code_lo")
 
+    def wait_until_config_writable(self, timeout_s=10, poll_interval_s=0.5):
+        deadline = time.time() + timeout_s
+        while time.time() < deadline:
+            if self.read("Main_state") in CONFIG_WRITABLE_STATES:
+                return
+            time.sleep(poll_interval_s)
+        raise ModbusDeviceError(f"RPU did not reach a config-writable state within {timeout_s}s")
+
     def rewrite_config(self):
         self.write_holding_register(self._addr("PASSWORD_LO"), self.REWRITE_PASSWORD_LO)
         self.write_holding_register(self._addr("PASSWORD_HI"), self.REWRITE_PASSWORD_HI)