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

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Message-ID: <20251127191808.144723-2-rakuram.e96@gmail.com>
Date: Fri, 28 Nov 2025 00:48:07 +0530
From: Rakuram Eswaran <rakuram.e96@...il.com>
To: linux-can@...r.kernel.org
Cc: mkl@...gutronix.de,
	socketcan@...tkopp.net,
	mailhol@...nel.org,
	khalid@...nel.org,
	skhan@...uxfoundation.org,
	linux-kernel@...r.kernel.org,
	rakuram.e96@...il.com,
	david.hunter.linux@...il.com,
	linux-kernel-mentees@...ts.linux.dev
Subject: [RFC 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

 drivers/net/can/dummy_can.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/net/can/dummy_can.c b/drivers/net/can/dummy_can.c
index 41953655e3d3..2949173547e6 100644
--- a/drivers/net/can/dummy_can.c
+++ b/drivers/net/can/dummy_can.c
@@ -23,6 +23,21 @@ struct dummy_can {
 
 static struct dummy_can *dummy_can;
 
+static const u16 dummy_can_termination_const[] = {
+	CAN_TERMINATION_DISABLED,	/* 0 = off */
+	120,				/* 120 Ohms */
+};
+
+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 const struct can_bittiming_const dummy_can_bittiming_const = {
 	.name = "dummy_can CC",
 	.tseg1_min = 2,
@@ -250,6 +265,12 @@ static int __init dummy_can_init(void)
 	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;
+	
+	/* Advertise software termination support */
+	priv->can.termination_const = dummy_can_termination_const;
+	priv->can.termination_const_cnt = ARRAY_SIZE(dummy_can_termination_const);
+	priv->can.do_set_termination = dummy_can_set_termination;
+
 	priv->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY |
 		CAN_CTRLMODE_FD | CAN_CTRLMODE_TDC_AUTO |
 		CAN_CTRLMODE_RESTRICTED | CAN_CTRLMODE_XL |
-- 
2.51.0