linux-kernel - [PATCH 1/2] can: dummy_can: add CAN termination support

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Message-ID: <20251231-can_doc_update_v1-v1-1-97aac5c20a35@gmail.com>
Date: Wed, 31 Dec 2025 23:43:15 +0530
From: Rakuram Eswaran <rakuram.e96@...il.com>
To: rakuram.e96@...il.com,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Vincent Mailhol <mailhol@...nel.org>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Jonathan Corbet <corbet@....net>
Cc: linux-can@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: [PATCH 1/2] can: dummy_can: add CAN termination support

Add support for configuring bus termination in the dummy_can driver.
This allows users to emulate a properly terminated CAN bus when
setting up virtual test environments.

Signed-off-by: Rakuram Eswaran <rakuram.e96@...il.com>
---
Tested the termination setting using below iproute commands:

  ip link set can0 type can termination 120
  ip link set can0 type can termination off
  ip link set can0 type can termination potato
  ip link set can0 type can termination 10000
  
 drivers/net/can/dummy_can.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/dummy_can.c b/drivers/net/can/dummy_can.c
index 41953655e3d3c9187d6574710e6aa90fc01c92a7..418d9e25bfca1c7af924ad451c8dd8ae1bca78a3 100644
--- a/drivers/net/can/dummy_can.c
+++ b/drivers/net/can/dummy_can.c
@@ -86,6 +86,11 @@ static const struct can_pwm_const dummy_can_pwm_const = {
 	.pwmo_max = 16,
 };
 
+static const u16 dummy_can_termination_const[] = {
+	CAN_TERMINATION_DISABLED,	/* 0 = off */
+	120,				/* 120 Ohms */
+};
+
 static void dummy_can_print_bittiming(struct net_device *dev,
 				      struct can_bittiming *bt)
 {
@@ -179,6 +184,16 @@ static void dummy_can_print_bittiming_info(struct net_device *dev)
 	netdev_dbg(dev, "\n");
 }
 
+static int dummy_can_set_termination(struct net_device *dev, u16 term)
+{
+	struct dummy_can *priv = netdev_priv(dev);
+
+	netdev_dbg(dev, "set termination to %u Ohms\n", term);
+	priv->can.termination = term;
+
+	return 0;
+}
+
 static int dummy_can_netdev_open(struct net_device *dev)
 {
 	int ret;
@@ -243,17 +258,23 @@ static int __init dummy_can_init(void)
 	dev->ethtool_ops = &dummy_can_ethtool_ops;
 	priv = netdev_priv(dev);
 	priv->can.bittiming_const = &dummy_can_bittiming_const;
-	priv->can.bitrate_max = 20 * MEGA /* BPS */;
-	priv->can.clock.freq = 160 * MEGA /* Hz */;
 	priv->can.fd.data_bittiming_const = &dummy_can_fd_databittiming_const;
 	priv->can.fd.tdc_const = &dummy_can_fd_tdc_const;
 	priv->can.xl.data_bittiming_const = &dummy_can_xl_databittiming_const;
 	priv->can.xl.tdc_const = &dummy_can_xl_tdc_const;
 	priv->can.xl.pwm_const = &dummy_can_pwm_const;
+	priv->can.bitrate_max = 20 * MEGA /* BPS */;
+	priv->can.clock.freq = 160 * MEGA /* Hz */;
+	priv->can.termination_const_cnt = ARRAY_SIZE(dummy_can_termination_const);
+	priv->can.termination_const = dummy_can_termination_const;
+
 	priv->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY |
 		CAN_CTRLMODE_FD | CAN_CTRLMODE_TDC_AUTO |
 		CAN_CTRLMODE_RESTRICTED | CAN_CTRLMODE_XL |
 		CAN_CTRLMODE_XL_TDC_AUTO | CAN_CTRLMODE_XL_TMS;
+
+	priv->can.do_set_termination = dummy_can_set_termination;
+
 	priv->dev = dev;
 
 	ret = register_candev(priv->dev);

-- 
2.51.0