[stm32] Allow using hardware buffers only in FDCAN driver

Author: chris-durand

src/modm/platform/can/stm32-fdcan/can.cpp.in

@@ -471,11 +471,9 @@ modm::platform::Fdcan{{ id }}::getMessage(can::Message& message, uint8_t *filter
 %% else
 	if (rxFifo0HasMessage()) {
 		readMsg(message, 0, filter_id, timestamp);
-		releaseRxFifo0Message();
 		return true;
 	} else if (rxFifo1HasMessage()) {
 		readMsg(message, 1, filter_id, timestamp);
-		releaseRxFifo1Message();
 		return true;
 	}
 	return false;

src/modm/platform/can/stm32-fdcan/module.lb

@@ -30,13 +30,13 @@ def load_options(module, options):
         NumericOption(
             name="buffer.tx",
             description="",
-            minimum=1, maximum="64Ki-2",
+            minimum=0, maximum="64Ki-2",
             default=32))
     module.add_option(
         NumericOption(
             name="buffer.rx",
             description="",
-            minimum=1, maximum="64Ki-2",
+            minimum=0, maximum="64Ki-2",
             default=32))
 
     supports_configurable_message_ram = options[":target"].identifier.family == "h7"