[RFC PATCH v2 0/2] add commandline support for Transmitter Delay Compensation (TDC) in iproute

[RFC PATCH v2 0/2] add commandline support for Transmitter Delay Compensation (TDC) in iproute

[Vincent Mailhol]

This patch series contains two patches which respectively:
  1. factorize the many print_*(PRINT_JSON, ...) and fprintf
  occurrences in a single print_*(PRINT_ANY, ...) call and fix the
  signedness while doing that.
  2. adds command line support for the TDC in iproute and goes together
  with below series in the kernel:
  https://lore.kernel.org/linux-can/20210506111412.1665835-1-mailhol.vincent@wanadoo.fr/T/#t

For now, I am only sending the kernel mailing list as an RFC. The
patch will be sent to iproute maintainers after the kernel patches
get accepted.


** Changelog **

From RFC v1 to RFC v2:
  * Add an additional patch to the series to fix the issues reported
    by Stephen Hemminger
    Ref: https://lore.kernel.org/linux-can/20210506112007.1666738-1-mailhol.vincent@wanadoo.fr/T/#t

Vincent Mailhol (2):
  iplink_can: use PRINT_ANY to factorize code and fix signedness
  iplink_can: add new CAN FD bittiming parameters: Transmitter Delay
    Compensation (TDC)

 include/uapi/linux/can/netlink.h |  25 +-
 ip/iplink_can.c                  | 402 ++++++++++++++++---------------
 2 files changed, 224 insertions(+), 203 deletions(-)

-- 
2.26.3

[RFC PATCH v2 1/2] iplink_can: use PRINT_ANY to factorize code and fix signedness

[Vincent Mailhol]

Current implementation heavily relies on some "if (is_json_context())"
switches to decide the context and then does some print_*(PRINT_JSON,
...) when in json context and some fprintf(...) else.

Furthermore, current implementation uses either print_int() or the
conversion specifier %d to print unsigned integers.

This patch factorizes each pairs of print_*(PRINT_JSON, ...) and
fprintf into a signle print_*(PRINT_ANY, ...) call. While doing this
replacement, it uses proper unsigned function print_uint() as well as
the conversion specifier %u when the parameter is an unsigned integer.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
 ip/iplink_can.c | 338 ++++++++++++++++++++----------------------------
 1 file changed, 138 insertions(+), 200 deletions(-)

diff --git a/ip/iplink_can.c b/ip/iplink_can.c
index 6a26f3ff..1421f0ea 100644
--- a/ip/iplink_can.c
+++ b/ip/iplink_can.c
@@ -266,14 +266,34 @@ static const char *can_state_names[CAN_STATE_MAX] = {
 	[CAN_STATE_SLEEPING] = "SLEEPING"
 };
 
-static void can_print_json_timing_min_max(const char *attr, int min, int max)
+static void can_print_nl_indent(void)
+{
+	print_nl();
+	print_string(PRINT_FP, NULL, "%s", "\t  ");
+}
+
+static void can_print_timing_min_max(const char *attr, int min, int max)
 {
 	open_json_object(attr);
-	print_int(PRINT_JSON, "min", NULL, min);
-	print_int(PRINT_JSON, "max", NULL, max);
+	print_uint(PRINT_ANY, "min", " %u", min);
+	print_uint(PRINT_ANY, "max", "..%u", max);
 	close_json_object();
 }
 
+/* Print nominal bittiming */
+static void can_print_nom_timing_min_max(const char *attr, int min, int max)
+{
+	print_string(PRINT_FP, NULL, " %s", attr);
+	can_print_timing_min_max(attr, min, max);
+}
+
+/* Print data bittiming: use a "d" prefix when printing to the file pointer */
+static void can_print_data_timing_min_max(const char *attr, int min, int max)
+{
+	print_string(PRINT_FP, NULL, " d%s", attr);
+	can_print_timing_min_max(attr, min, max);
+}
+
 static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 {
 	if (!tb)
@@ -297,56 +317,38 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 		struct can_berr_counter *bc =
 			RTA_DATA(tb[IFLA_CAN_BERR_COUNTER]);
 
-		if (is_json_context()) {
-			open_json_object("berr_counter");
-			print_int(PRINT_JSON, "tx", NULL, bc->txerr);
-			print_int(PRINT_JSON, "rx", NULL, bc->rxerr);
-			close_json_object();
-		} else {
-			fprintf(f, "(berr-counter tx %d rx %d) ",
-				bc->txerr, bc->rxerr);
-		}
+		open_json_object("berr_counter");
+		print_uint(PRINT_ANY, "tx", "(berr-counter tx %u", bc->txerr);
+		print_uint(PRINT_ANY, "rx", " rx %u) ", bc->rxerr);
+		close_json_object();
 	}
 
 	if (tb[IFLA_CAN_RESTART_MS]) {
 		__u32 *restart_ms = RTA_DATA(tb[IFLA_CAN_RESTART_MS]);
 
-		print_int(PRINT_ANY,
-			  "restart_ms",
-			  "restart-ms %d ",
-			  *restart_ms);
+		print_uint(PRINT_ANY, "restart_ms", "restart-ms %u ",
+			   *restart_ms);
 	}
 
 	/* bittiming is irrelevant if fixed bitrate is defined */
 	if (tb[IFLA_CAN_BITTIMING] && !tb[IFLA_CAN_BITRATE_CONST]) {
 		struct can_bittiming *bt = RTA_DATA(tb[IFLA_CAN_BITTIMING]);
-
-		if (is_json_context()) {
-			json_writer_t *jw;
-
-			open_json_object("bittiming");
-			print_int(PRINT_ANY, "bitrate", NULL, bt->bitrate);
-			jw = get_json_writer();
-			jsonw_name(jw, "sample_point");
-			jsonw_printf(jw, "%.3f",
-				     (float) bt->sample_point / 1000);
-			print_int(PRINT_ANY, "tq", NULL, bt->tq);
-			print_int(PRINT_ANY, "prop_seg", NULL, bt->prop_seg);
-			print_int(PRINT_ANY, "phase_seg1",
-				  NULL, bt->phase_seg1);
-			print_int(PRINT_ANY, "phase_seg2",
-				  NULL, bt->phase_seg2);
-			print_int(PRINT_ANY, "sjw", NULL, bt->sjw);
-			close_json_object();
-		} else {
-			fprintf(f, "\n	  bitrate %d sample-point %.3f ",
-				bt->bitrate, (float) bt->sample_point / 1000.);
-			fprintf(f,
-				"\n	  tq %d prop-seg %d phase-seg1 %d phase-seg2 %d sjw %d",
-				bt->tq, bt->prop_seg,
-				bt->phase_seg1, bt->phase_seg2,
-				bt->sjw);
-		}
+		char sp[6];
+
+		open_json_object("bittiming");
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "bitrate", "bitrate %u", bt->bitrate);
+		snprintf(sp, sizeof(sp), "%.3f", bt->sample_point / 1000.);
+		print_string(PRINT_ANY, "sample_point", " sample-point %s", sp);
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "tq", "tq %u", bt->tq);
+		print_uint(PRINT_ANY, "prop_seg", " prop-seg %u", bt->prop_seg);
+		print_uint(PRINT_ANY, "phase_seg1", " phase-seg1 %u",
+			   bt->phase_seg1);
+		print_uint(PRINT_ANY, "phase_seg2", "phase-seg2 %u ",
+			   bt->phase_seg2);
+		print_uint(PRINT_ANY, "sjw", " sjw %u", bt->sjw);
+		close_json_object();
 	}
 
 	/* bittiming const is irrelevant if fixed bitrate is defined */
@@ -354,28 +356,18 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 		struct can_bittiming_const *btc =
 			RTA_DATA(tb[IFLA_CAN_BITTIMING_CONST]);
 
-		if (is_json_context()) {
-			open_json_object("bittiming_const");
-			print_string(PRINT_JSON, "name", NULL, btc->name);
-			can_print_json_timing_min_max("tseg1",
-						      btc->tseg1_min,
-						      btc->tseg1_max);
-			can_print_json_timing_min_max("tseg2",
-						      btc->tseg2_min,
-						      btc->tseg2_max);
-			can_print_json_timing_min_max("sjw", 1, btc->sjw_max);
-			can_print_json_timing_min_max("brp",
-						      btc->brp_min,
-						      btc->brp_max);
-			print_int(PRINT_JSON, "brp_inc", NULL, btc->brp_inc);
-			close_json_object();
-		} else {
-			fprintf(f, "\n	  %s: tseg1 %d..%d tseg2 %d..%d "
-				"sjw 1..%d brp %d..%d brp-inc %d",
-				btc->name, btc->tseg1_min, btc->tseg1_max,
-				btc->tseg2_min, btc->tseg2_max, btc->sjw_max,
-				btc->brp_min, btc->brp_max, btc->brp_inc);
-		}
+		open_json_object("bittiming_const");
+		can_print_nl_indent();
+		print_string(PRINT_ANY, "name", "%s:", btc->name);
+		can_print_nom_timing_min_max("tseg1",
+					     btc->tseg1_min, btc->tseg1_max);
+		can_print_nom_timing_min_max("tseg2",
+					     btc->tseg2_min, btc->tseg2_max);
+		can_print_nom_timing_min_max("sjw", 1, btc->sjw_max);
+		can_print_nom_timing_min_max("brp",
+					     btc->brp_min, btc->brp_max);
+		print_uint(PRINT_ANY, "brp_inc", " brp_inc %u", btc->brp_inc);
+		close_json_object();
 	}
 
 	if (tb[IFLA_CAN_BITRATE_CONST]) {
@@ -391,64 +383,46 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 			bitrate = bt->bitrate;
 		}
 
-		if (is_json_context()) {
-			print_uint(PRINT_JSON,
-				   "bittiming_bitrate",
-				   NULL, bitrate);
-			open_json_array(PRINT_JSON, "bitrate_const");
-			for (i = 0; i < bitrate_cnt; ++i)
-				print_uint(PRINT_JSON, NULL, NULL,
-					   bitrate_const[i]);
-			close_json_array(PRINT_JSON, NULL);
-		} else {
-			fprintf(f, "\n	  bitrate %u", bitrate);
-			fprintf(f, "\n	     [");
-
-			for (i = 0; i < bitrate_cnt - 1; ++i) {
-				/* This will keep lines below 80 signs */
-				if (!(i % 6) && i)
-					fprintf(f, "\n	      ");
-
-				fprintf(f, "%8u, ", bitrate_const[i]);
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "bittiming_bitrate", "bitrate %u",
+			   bitrate);
+		can_print_nl_indent();
+		open_json_array(PRINT_ANY, is_json_context() ?
+				"bitrate_const" : "   [");
+		for (i = 0; i < bitrate_cnt - 1; ++i) {
+			/* This will keep lines below 80 signs */
+			if (!(i % 6) && i) {
+				can_print_nl_indent();
+				print_string(PRINT_FP, NULL, "%s", "    ");
 			}
-
-			if (!(i % 6) && i)
-				fprintf(f, "\n	      ");
-			fprintf(f, "%8u ]", bitrate_const[i]);
+			print_uint(PRINT_ANY, NULL, "%8u, ", bitrate_const[i]);
 		}
+		print_uint(PRINT_ANY, NULL, "%8u", bitrate_const[i]);
+		close_json_array(PRINT_JSON, " ]");
 	}
 
 	/* data bittiming is irrelevant if fixed bitrate is defined */
 	if (tb[IFLA_CAN_DATA_BITTIMING] && !tb[IFLA_CAN_DATA_BITRATE_CONST]) {
 		struct can_bittiming *dbt =
 			RTA_DATA(tb[IFLA_CAN_DATA_BITTIMING]);
-
-		if (is_json_context()) {
-			json_writer_t *jw;
-
-			open_json_object("data_bittiming");
-			print_int(PRINT_JSON, "bitrate", NULL, dbt->bitrate);
-			jw = get_json_writer();
-			jsonw_name(jw, "sample_point");
-			jsonw_printf(jw, "%.3f",
-				     (float) dbt->sample_point / 1000.);
-			print_int(PRINT_JSON, "tq", NULL, dbt->tq);
-			print_int(PRINT_JSON, "prop_seg", NULL, dbt->prop_seg);
-			print_int(PRINT_JSON, "phase_seg1",
-				  NULL, dbt->phase_seg1);
-			print_int(PRINT_JSON, "phase_seg2",
-				  NULL, dbt->phase_seg2);
-			print_int(PRINT_JSON, "sjw", NULL, dbt->sjw);
-			close_json_object();
-		} else {
-			fprintf(f, "\n	  dbitrate %d dsample-point %.3f ",
-				dbt->bitrate,
-				(float) dbt->sample_point / 1000.);
-			fprintf(f, "\n	  dtq %d dprop-seg %d dphase-seg1 %d "
-				"dphase-seg2 %d dsjw %d",
-				dbt->tq, dbt->prop_seg, dbt->phase_seg1,
-				dbt->phase_seg2, dbt->sjw);
-		}
+		char dsp[6];
+
+		open_json_object("data_bittiming");
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "bitrate", "dbitrate %u", dbt->bitrate);
+		snprintf(dsp, sizeof(dsp), "%.3f", dbt->sample_point / 1000.);
+		print_string(PRINT_ANY, "sample_point", " dsample-point %s",
+			     dsp);
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "tq", "dtq %u", dbt->tq);
+		print_uint(PRINT_ANY, "prop_seg", " dprop-seg %u",
+			   dbt->prop_seg);
+		print_uint(PRINT_ANY, "phase_seg1", " dphase-seg1 %u",
+			   dbt->phase_seg1);
+		print_uint(PRINT_ANY, "phase_seg2", " dphase-seg2 %u",
+			   dbt->phase_seg2);
+		print_uint(PRINT_ANY, "sjw", " dsjw %u", dbt->sjw);
+		close_json_object();
 	}
 
 	/* data bittiming const is irrelevant if fixed bitrate is defined */
@@ -457,29 +431,18 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 		struct can_bittiming_const *dbtc =
 			RTA_DATA(tb[IFLA_CAN_DATA_BITTIMING_CONST]);
 
-		if (is_json_context()) {
-			open_json_object("data_bittiming_const");
-			print_string(PRINT_JSON, "name", NULL, dbtc->name);
-			can_print_json_timing_min_max("tseg1",
-						      dbtc->tseg1_min,
-						      dbtc->tseg1_max);
-			can_print_json_timing_min_max("tseg2",
-						      dbtc->tseg2_min,
-						      dbtc->tseg2_max);
-			can_print_json_timing_min_max("sjw", 1, dbtc->sjw_max);
-			can_print_json_timing_min_max("brp",
-						      dbtc->brp_min,
-						      dbtc->brp_max);
-
-			print_int(PRINT_JSON, "brp_inc", NULL, dbtc->brp_inc);
-			close_json_object();
-		} else {
-			fprintf(f, "\n	  %s: dtseg1 %d..%d dtseg2 %d..%d "
-				"dsjw 1..%d dbrp %d..%d dbrp-inc %d",
-				dbtc->name, dbtc->tseg1_min, dbtc->tseg1_max,
-				dbtc->tseg2_min, dbtc->tseg2_max, dbtc->sjw_max,
-				dbtc->brp_min, dbtc->brp_max, dbtc->brp_inc);
-		}
+		open_json_object("data_bittiming_const");
+		can_print_nl_indent();
+		print_string(PRINT_ANY, "name", "%s:", dbtc->name);
+		can_print_data_timing_min_max("tseg1",
+					      dbtc->tseg1_min, dbtc->tseg1_max);
+		can_print_data_timing_min_max("tseg2",
+					      dbtc->tseg2_min, dbtc->tseg2_max);
+		can_print_data_timing_min_max("sjw", 1, dbtc->sjw_max);
+		can_print_data_timing_min_max("brp",
+					      dbtc->brp_min, dbtc->brp_max);
+		print_uint(PRINT_ANY, "brp_inc", " brp_inc %u", dbtc->brp_inc);
+		close_json_object();
 	}
 
 	if (tb[IFLA_CAN_DATA_BITRATE_CONST]) {
@@ -497,30 +460,22 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 			dbitrate = dbt->bitrate;
 		}
 
-		if (is_json_context()) {
-			print_uint(PRINT_JSON, "data_bittiming_bitrate",
-				   NULL, dbitrate);
-			open_json_array(PRINT_JSON, "data_bitrate_const");
-			for (i = 0; i < dbitrate_cnt; ++i)
-				print_uint(PRINT_JSON, NULL, NULL,
-					   dbitrate_const[i]);
-			close_json_array(PRINT_JSON, NULL);
-		} else {
-			fprintf(f, "\n	  dbitrate %u", dbitrate);
-			fprintf(f, "\n	     [");
-
-			for (i = 0; i < dbitrate_cnt - 1; ++i) {
-				/* This will keep lines below 80 signs */
-				if (!(i % 6) && i)
-					fprintf(f, "\n	      ");
-
-				fprintf(f, "%8u, ", dbitrate_const[i]);
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "data_bittiming_bitrate", "dbitrate %u",
+			   dbitrate);
+		can_print_nl_indent();
+		open_json_array(PRINT_ANY, is_json_context() ?
+				"data_bitrate_const" : "   [");
+		for (i = 0; i < dbitrate_cnt - 1; ++i) {
+			/* This will keep lines below 80 signs */
+			if (!(i % 6) && i) {
+				can_print_nl_indent();
+				print_string(PRINT_FP, NULL, "%s", "    ");
 			}
-
-			if (!(i % 6) && i)
-				fprintf(f, "\n	      ");
-			fprintf(f, "%8u ]", dbitrate_const[i]);
+			print_uint(PRINT_ANY, NULL, "%8u, ", dbitrate_const[i]);
 		}
+		print_uint(PRINT_ANY, NULL, "%8u", dbitrate_const[i]);
+		close_json_array(PRINT_JSON, " ]");
 	}
 
 	if (tb[IFLA_CAN_TERMINATION_CONST] && tb[IFLA_CAN_TERMINATION]) {
@@ -530,29 +485,20 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 			sizeof(*trm_const);
 		int i;
 
-		if (is_json_context()) {
-			print_hu(PRINT_JSON, "termination", NULL, *trm);
-			open_json_array(PRINT_JSON, "termination_const");
-			for (i = 0; i < trm_cnt; ++i)
-				print_hu(PRINT_JSON, NULL, NULL, trm_const[i]);
-			close_json_array(PRINT_JSON, NULL);
-		} else {
-			fprintf(f, "\n	  termination %hu [ ", *trm);
-
-			for (i = 0; i < trm_cnt - 1; ++i)
-				fprintf(f, "%hu, ", trm_const[i]);
-
-			fprintf(f, "%hu ]", trm_const[i]);
-		}
+		can_print_nl_indent();
+		print_hu(PRINT_ANY, "termination", "termination %hu [ ", *trm);
+		open_json_array(PRINT_JSON, "termination_const");
+		for (i = 0; i < trm_cnt - 1; ++i)
+			print_hu(PRINT_ANY, NULL, "%hu, ", trm_const[i]);
+		print_hu(PRINT_ANY, NULL, "%hu", trm_const[i]);
+		close_json_array(PRINT_JSON, " ]");
 	}
 
 	if (tb[IFLA_CAN_CLOCK]) {
 		struct can_clock *clock = RTA_DATA(tb[IFLA_CAN_CLOCK]);
 
-		print_int(PRINT_ANY,
-			  "clock",
-			  "\n	  clock %d ",
-			  clock->freq);
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "clock", "clock %u ", clock->freq);
 	}
 
 }
@@ -565,31 +511,23 @@ static void can_print_xstats(struct link_util *lu,
 	if (xstats && RTA_PAYLOAD(xstats) == sizeof(*stats)) {
 		stats = RTA_DATA(xstats);
 
-		if (is_json_context()) {
-			print_int(PRINT_JSON, "restarts",
-				  NULL, stats->restarts);
-			print_int(PRINT_JSON, "bus_error",
-				  NULL, stats->bus_error);
-			print_int(PRINT_JSON, "arbitration_lost",
-				  NULL, stats->arbitration_lost);
-			print_int(PRINT_JSON, "error_warning",
-				  NULL, stats->error_warning);
-			print_int(PRINT_JSON, "error_passive",
-				  NULL, stats->error_passive);
-			print_int(PRINT_JSON, "bus_off", NULL, stats->bus_off);
-		} else {
-			fprintf(f, "\n	  re-started bus-errors arbit-lost "
-				"error-warn error-pass bus-off");
-			fprintf(f, "\n	  %-10d %-10d %-10d %-10d %-10d %-10d",
-				stats->restarts, stats->bus_error,
-				stats->arbitration_lost, stats->error_warning,
-				stats->error_passive, stats->bus_off);
-		}
+		can_print_nl_indent();
+		print_string(PRINT_FP, NULL, "%s",
+			     "re-started bus-errors arbit-lost error-warn error-pass bus-off");
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "restarts", "%-10u", stats->restarts);
+		print_uint(PRINT_ANY, "bus_error", " %-10u", stats->bus_error);
+		print_uint(PRINT_ANY, "arbitration_lost", " %-10u",
+			   stats->arbitration_lost);
+		print_uint(PRINT_ANY, "error_warning", " %-10u",
+			   stats->error_warning);
+		print_uint(PRINT_ANY, "error_passive", " %-10u",
+			   stats->error_passive);
+		print_uint(PRINT_ANY, "bus_off", " %-10u", stats->bus_off);
 	}
 }
 
-static void can_print_help(struct link_util *lu, int argc, char **argv,
-			   FILE *f)
+static void can_print_help(struct link_util *lu, int argc, char **argv, FILE *f)
 {
 	print_usage(f);
 }
-- 
2.26.3

[RFC PATCH v2 2/2] iplink_can: add new CAN FD bittiming parameters: Transmitter Delay Compensation (TDC)

[Vincent Mailhol]

At high bit rates, the propagation delay from the TX pin to the RX pin
of the transceiver causes measurement errors: the sample point on the
RX pin might occur on the previous bit.

This issue is addressed in ISO 11898-1 section 11.3.3 "Transmitter
delay compensation" (TDC).

This patch brings command line support to six TDC parameters which
were recently added to the kernel's CAN netlink interface in order to
implement TDC:
  - IFLA_CAN_TDC_TDCV_MAX: Transmitter Delay Compensation Value
    maximum value
  - IFLA_CAN_TDC_TDCO_MAX: Transmitter Delay Compensation Offset
    maximum value
  - IFLA_CAN_TDC_TDCF_MAX: Transmitter Delay Compensation Filter
    window maximum value
  - IFLA_CAN_TDC_TDCV: Transmitter Delay Compensation Value
  - IFLA_CAN_TDC_TDCO: Transmitter Delay Compensation Offset
  - IFLA_CAN_TDC_TDCF: Transmitter Delay Compensation Filter window

All those new parameters are nested together into the attribute
IFLA_CAN_TDC.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
 include/uapi/linux/can/netlink.h | 25 +++++++++++--
 ip/iplink_can.c                  | 64 ++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/can/netlink.h b/include/uapi/linux/can/netlink.h
index 00c763df..d5cc2761 100644
--- a/include/uapi/linux/can/netlink.h
+++ b/include/uapi/linux/can/netlink.h
@@ -134,12 +134,31 @@ enum {
 	IFLA_CAN_BITRATE_CONST,
 	IFLA_CAN_DATA_BITRATE_CONST,
 	IFLA_CAN_BITRATE_MAX,
-	__IFLA_CAN_MAX
-};
+	IFLA_CAN_TDC,
 
-#define IFLA_CAN_MAX	(__IFLA_CAN_MAX - 1)
+	/* add new constants above here */
+	__IFLA_CAN_MAX,
+	IFLA_CAN_MAX = __IFLA_CAN_MAX - 1
+};
 
 /* u16 termination range: 1..65535 Ohms */
 #define CAN_TERMINATION_DISABLED 0
 
+/*
+ * CAN FD Transmitter Delay Compensation (TDC)
+ */
+enum {
+	IFLA_CAN_TDC_UNSPEC,
+	IFLA_CAN_TDC_TDCV_MAX,	/* u32 */
+	IFLA_CAN_TDC_TDCO_MAX,	/* u32 */
+	IFLA_CAN_TDC_TDCF_MAX,	/* u32 */
+	IFLA_CAN_TDC_TDCV,	/* u32 */
+	IFLA_CAN_TDC_TDCO,	/* u32 */
+	IFLA_CAN_TDC_TDCF,	/* u32 */
+
+	/* add new constants above here */
+	__IFLA_CAN_TDC,
+	IFLA_CAN_TDC_MAX = __IFLA_CAN_TDC - 1
+};
+
 #endif /* !_UAPI_CAN_NETLINK_H */
diff --git a/ip/iplink_can.c b/ip/iplink_can.c
index 1421f0ea..8c2f6beb 100644
--- a/ip/iplink_can.c
+++ b/ip/iplink_can.c
@@ -28,6 +28,7 @@ static void print_usage(FILE *f)
 		"\n"
 		"\t[ dbitrate BITRATE [ dsample-point SAMPLE-POINT] ] |\n"
 		"\t[ dtq TQ dprop-seg PROP_SEG dphase-seg1 PHASE-SEG1\n \t  dphase-seg2 PHASE-SEG2 [ dsjw SJW ] ]\n"
+		"\t[ tdcv TDCV tdco TDCO tdcf TDCF ]\n"
 		"\n"
 		"\t[ loopback { on | off } ]\n"
 		"\t[ listen-only { on | off } ]\n"
@@ -52,6 +53,9 @@ static void print_usage(FILE *f)
 		"\t	  PHASE-SEG2	:= { 1..8 }\n"
 		"\t	  SJW		:= { 1..4 }\n"
 		"\t	  RESTART-MS	:= { 0 | NUMBER }\n"
+		"\t	  TDCV		:= { NUMBER }\n"
+		"\t	  TDCO		:= { NUMBER }\n"
+		"\t	  TDCF		:= { NUMBER }\n"
 		);
 }
 
@@ -116,6 +120,8 @@ static int can_parse_opt(struct link_util *lu, int argc, char **argv,
 {
 	struct can_bittiming bt = {}, dbt = {};
 	struct can_ctrlmode cm = {0, 0};
+	struct rtattr *tdc;
+	__u32 tdcv = -1, tdco = -1, tdcf = -1;
 
 	while (argc > 0) {
 		if (matches(*argv, "bitrate") == 0) {
@@ -181,6 +187,18 @@ static int can_parse_opt(struct link_util *lu, int argc, char **argv,
 			NEXT_ARG();
 			if (get_u32(&dbt.sjw, *argv, 0))
 				invarg("invalid \"dsjw\" value\n", *argv);
+		} else if (matches(*argv, "tdcv") == 0) {
+			NEXT_ARG();
+			if (get_u32(&tdcv, *argv, 0))
+				invarg("invalid \"tdcv\" value\n", *argv);
+		} else if (matches(*argv, "tdco") == 0) {
+			NEXT_ARG();
+			if (get_u32(&tdco, *argv, 0))
+				invarg("invalid \"tdco\" value\n", *argv);
+		} else if (matches(*argv, "tdcf") == 0) {
+			NEXT_ARG();
+			if (get_u32(&tdcf, *argv, 0))
+				invarg("invalid \"tdcf\" value\n", *argv);
 		} else if (matches(*argv, "loopback") == 0) {
 			NEXT_ARG();
 			set_ctrlmode("loopback", *argv, &cm,
@@ -254,6 +272,15 @@ static int can_parse_opt(struct link_util *lu, int argc, char **argv,
 	if (cm.mask)
 		addattr_l(n, 1024, IFLA_CAN_CTRLMODE, &cm, sizeof(cm));
 
+	tdc = addattr_nest(n, 1024, IFLA_CAN_TDC | NLA_F_NESTED);
+	if (tdcv != -1)
+		addattr32(n, 1024, IFLA_CAN_TDC_TDCV, tdcv);
+	if (tdco != -1)
+		addattr32(n, 1024, IFLA_CAN_TDC_TDCO, tdco);
+	if (tdcf != -1)
+		addattr32(n, 1024, IFLA_CAN_TDC_TDCF, tdcf);
+	addattr_nest_end(n, tdc);
+
 	return 0;
 }
 
@@ -294,6 +321,40 @@ static void can_print_data_timing_min_max(const char *attr, int min, int max)
 	can_print_timing_min_max(attr, min, max);
 }
 
+static void can_print_tdc_opt(FILE *f, struct rtattr *tdc_attr)
+{
+	struct rtattr *tb[IFLA_CAN_TDC_MAX + 1];
+
+	parse_rtattr_nested(tb, IFLA_CAN_TDC_MAX, tdc_attr);
+	if (tb[IFLA_CAN_TDC_TDCV] && tb[IFLA_CAN_TDC_TDCO] &&
+	    tb[IFLA_CAN_TDC_TDCF]) {
+		__u32 *tdcv = RTA_DATA(tb[IFLA_CAN_TDC_TDCV]);
+		__u32 *tdco = RTA_DATA(tb[IFLA_CAN_TDC_TDCO]);
+		__u32 *tdcf = RTA_DATA(tb[IFLA_CAN_TDC_TDCF]);
+
+		open_json_object("tdc");
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "tdcv", "tdcv %u", *tdcv);
+		print_uint(PRINT_ANY, "tdco", " tdco %u", *tdco);
+		print_uint(PRINT_ANY, "tdcf", " tdcf %u", *tdcf);
+		close_json_object();
+	}
+
+	if (tb[IFLA_CAN_TDC_TDCV_MAX] && tb[IFLA_CAN_TDC_TDCO_MAX] &&
+	    tb[IFLA_CAN_TDC_TDCF_MAX]) {
+		__u32 *tdcv_max = RTA_DATA(tb[IFLA_CAN_TDC_TDCV_MAX]);
+		__u32 *tdco_max = RTA_DATA(tb[IFLA_CAN_TDC_TDCO_MAX]);
+		__u32 *tdcf_max = RTA_DATA(tb[IFLA_CAN_TDC_TDCF_MAX]);
+
+		open_json_object("tdc_const");
+		can_print_nl_indent();
+		print_uint(PRINT_ANY, "tdcv_max", "tdcv_max %u", *tdcv_max);
+		print_uint(PRINT_ANY, "tdco_max", " tdco_max %u", *tdco_max);
+		print_uint(PRINT_ANY, "tdcf_max", " tdcf_max %u", *tdcf_max);
+		close_json_object();
+	}
+}
+
 static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 {
 	if (!tb)
@@ -478,6 +539,9 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 		close_json_array(PRINT_JSON, " ]");
 	}
 
+	if (tb[IFLA_CAN_TDC])
+		can_print_tdc_opt(f, tb[IFLA_CAN_TDC]);
+
 	if (tb[IFLA_CAN_TERMINATION_CONST] && tb[IFLA_CAN_TERMINATION]) {
 		__u16 *trm = RTA_DATA(tb[IFLA_CAN_TERMINATION]);
 		__u16 *trm_const = RTA_DATA(tb[IFLA_CAN_TERMINATION_CONST]);
-- 
2.26.3