linux-kernel - [PATCH can-next v8 12/17] can: calc_bittiming: replace misleading "nominal" by "reference"

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Message-Id: <20251126-canxl-v8-12-e7e3eb74f889@pengutronix.de>
Date: Wed, 26 Nov 2025 11:16:13 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Marc Kleine-Budde <mkl@...gutronix.de>, 
 Vincent Mailhol <mailhol@...nel.org>, 
 Oliver Hartkopp <socketcan@...tkopp.net>
Cc: kernel@...gutronix.de, linux-can@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Stéphane Grosjean <stephane.grosjean@...-networks.com>
Subject: [PATCH can-next v8 12/17] can: calc_bittiming: replace misleading
 "nominal" by "reference"

From: Vincent Mailhol <mailhol@...nel.org>

The functions can_update_sample_point() and can_calc_bittiming() are
generic and meant to be used for both the nominal and the data bittiming
calculation.

However, those functions use misleading terminologies such as "bitrate
nominal" or "sample point nominal". Replace all places where the word
"nominal" appears with "reference" in order to better distinguish it from
the calculated values.

Signed-off-by: Vincent Mailhol <mailhol@...nel.org>
Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/dev/calc_bittiming.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/net/can/dev/calc_bittiming.c b/drivers/net/can/dev/calc_bittiming.c
index 268ec6fa7c49..c8c166b383cd 100644
--- a/drivers/net/can/dev/calc_bittiming.c
+++ b/drivers/net/can/dev/calc_bittiming.c
@@ -24,7 +24,7 @@
  */
 static int
 can_update_sample_point(const struct can_bittiming_const *btc,
-			const unsigned int sample_point_nominal, const unsigned int tseg,
+			const unsigned int sample_point_reference, const unsigned int tseg,
 			unsigned int *tseg1_ptr, unsigned int *tseg2_ptr,
 			unsigned int *sample_point_error_ptr)
 {
@@ -35,7 +35,7 @@ can_update_sample_point(const struct can_bittiming_const *btc,
 
 	for (i = 0; i <= 1; i++) {
 		tseg2 = tseg + CAN_SYNC_SEG -
-			(sample_point_nominal * (tseg + CAN_SYNC_SEG)) /
+			(sample_point_reference * (tseg + CAN_SYNC_SEG)) /
 			1000 - i;
 		tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
 		tseg1 = tseg - tseg2;
@@ -46,9 +46,9 @@ can_update_sample_point(const struct can_bittiming_const *btc,
 
 		sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) /
 			(tseg + CAN_SYNC_SEG);
-		sample_point_error = abs(sample_point_nominal - sample_point);
+		sample_point_error = abs(sample_point_reference - sample_point);
 
-		if (sample_point <= sample_point_nominal &&
+		if (sample_point <= sample_point_reference &&
 		    sample_point_error < best_sample_point_error) {
 			best_sample_point = sample_point;
 			best_sample_point_error = sample_point_error;
@@ -68,11 +68,11 @@ int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
 {
 	struct can_priv *priv = netdev_priv(dev);
 	unsigned int bitrate;			/* current bitrate */
-	unsigned int bitrate_error;		/* difference between current and nominal value */
+	unsigned int bitrate_error;		/* diff between calculated and reference value */
 	unsigned int best_bitrate_error = UINT_MAX;
-	unsigned int sample_point_error;	/* difference between current and nominal value */
+	unsigned int sample_point_error;	/* diff between calculated and reference value */
 	unsigned int best_sample_point_error = UINT_MAX;
-	unsigned int sample_point_nominal;	/* nominal sample point */
+	unsigned int sample_point_reference;	/* reference sample point */
 	unsigned int best_tseg = 0;		/* current best value for tseg */
 	unsigned int best_brp = 0;		/* current best value for brp */
 	unsigned int brp, tsegall, tseg, tseg1 = 0, tseg2 = 0;
@@ -81,14 +81,14 @@ int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
 
 	/* Use CiA recommended sample points */
 	if (bt->sample_point) {
-		sample_point_nominal = bt->sample_point;
+		sample_point_reference = bt->sample_point;
 	} else {
 		if (bt->bitrate > 800 * KILO /* BPS */)
-			sample_point_nominal = 750;
+			sample_point_reference = 750;
 		else if (bt->bitrate > 500 * KILO /* BPS */)
-			sample_point_nominal = 800;
+			sample_point_reference = 800;
 		else
-			sample_point_nominal = 875;
+			sample_point_reference = 875;
 	}
 
 	/* tseg even = round down, odd = round up */
@@ -115,7 +115,7 @@ int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
 		if (bitrate_error < best_bitrate_error)
 			best_sample_point_error = UINT_MAX;
 
-		can_update_sample_point(btc, sample_point_nominal, tseg / 2,
+		can_update_sample_point(btc, sample_point_reference, tseg / 2,
 					&tseg1, &tseg2, &sample_point_error);
 		if (sample_point_error >= best_sample_point_error)
 			continue;
@@ -146,7 +146,7 @@ int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
 	}
 
 	/* real sample point */
-	bt->sample_point = can_update_sample_point(btc, sample_point_nominal,
+	bt->sample_point = can_update_sample_point(btc, sample_point_reference,
 						   best_tseg, &tseg1, &tseg2,
 						   NULL);
 

-- 
2.51.0