drivers: can: mcux: flexcan: allow configuring max filters from 0 to 128

The maximum number of RX filters is limited by the number of message
buffers, which cannot exceed 128. Add a range to the Kconfig option
imposing this.

Remove artificial build-time check on CONFIG_CAN_MCUX_FLEXCAN_MAX_FILTERS
being larger than zero, as transmit-only configuration is otherwise fully
supported.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>

Author: henrikbrixandersen

drivers/can/Kconfig.mcux

@@ -29,13 +29,14 @@ config CAN_MCUX_FLEXCAN_WAIT_TIMEOUT
 	  freeze mode.
 
 config CAN_MCUX_FLEXCAN_MAX_FILTERS
-	int "Maximum number of concurrent active RX filters"
+	int "Maximum number of concurrently active RX filters"
+	range 0 128
 	default 5 if CAN_MCUX_FLEXCAN_FD
 	default 13
 	help
-	  Defines maximum number of concurrent active RX filters
-	  The maximum value depends on the number of available message
-	  buffers for each FlexCAN instance. CAN FD mode uses larger
-	  message buffers, resulting in fewer available filters.
+	  Defines maximum number of concurrently active RX filters. The maximum value depends on the
+	  number of available message buffers for each FlexCAN instance.
+
+	  CAN FD mode uses larger message buffers, resulting in fewer available filters.
 
 endif # CAN_MCUX_FLEXCAN

drivers/can/can_mcux_flexcan.c

@@ -1537,8 +1537,6 @@ static DEVICE_API(can, mcux_flexcan_fd_driver_api) = {
 			"FlexCAN instance " STRINGIFY(id) " clk-source without named clock")))
 
 #define FLEXCAN_CHECK_MAX_FILTER(id)						\
-	BUILD_ASSERT(CONFIG_CAN_MCUX_FLEXCAN_MAX_FILTERS > 0,			\
-		"Maximum number of RX filters should greater than 0");		\
 	BUILD_ASSERT(FLEXCAN_INST_NUMBER_OF_MB(id) > FLEXCAN_INST_RX_MB(id),	\
 		     "FlexCAN instance " STRINGIFY(id) " number-of-mb ("	\
 		     STRINGIFY(FLEXCAN_INST_NUMBER_OF_MB(id))			\

dts/bindings/can/nxp,flexcan.yaml

@@ -48,7 +48,8 @@ properties:
       - 128
     required: true
     description: |
-      Number of 8-byte sized message buffers supported by this FlexCAN instance.
+      Number of 8-byte sized message buffers (MBs) supported by this FlexCAN instance. CAN FD mode,
+      if supported, uses 64-byte sized MBs, resulting in fewer available MBs.
 
 examples:
   - |