can: netlink: Add CAN_CTRLMODE_PRESUME_ACK flag

Most CAN controllers have a support for ignoring ACK absence. Some of
them refer to this feature as a self test mode (e. g. SJA1000) and some
include it as a part of a loopback mode (e. g. MCP2510).

Setting the introduced flag via netlink should make CAN controller
perform a successful transmission, even if there is no acknowledgement
(dominant ACK bit) received.
Signed-off-by: NNikita Edward Baruzdin <nebaruzdin@gmail.com>
Acked-by: NOliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

include/uapi/linux/can/netlink.h

@@ -97,6 +97,7 @@ struct can_ctrlmode {
 #define CAN_CTRLMODE_ONE_SHOT		0x08	/* One-Shot mode */
 #define CAN_CTRLMODE_BERR_REPORTING	0x10	/* Bus-error reporting */
 #define CAN_CTRLMODE_FD			0x20	/* CAN FD mode */
+#define CAN_CTRLMODE_PRESUME_ACK	0x40	/* Ignore missing CAN ACKs */
 
 /*
  * CAN device statistics