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@gmail.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

On 31/12/2025 at 19:13, Rakuram Eswaran wrote:
> 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@gmail.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 */

Nitpick: no need to explain that disabled means "off", the first comment
can be removed. Also, to be consistent with how the can.bitrate_max and
can.clock.freq are declared, you can add the unit just next to the value.

	static const u16 dummy_can_termination_const[] = {
		CAN_TERMINATION_DISABLED,
		120 /* Ohms */,
	};

(above comment is notwithstanding).

> +};
> +
>  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 */;

Don't add unrelated changes to your patch. Your patch should do one
thing (here: add the resistance termination). If you want to reorder the
existing lines, that should go in a separate clean-up patch. But here,
there is no need to touch those lines, so just drop this reorder.

>  	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);

Aside from the above remark this is OK. Please send a v2 with that last
remark addressed. You can also add my review tag:

Reviewed-by: Vincent Mailhol <mailhol@kernel.org>


Yours sincerely,
Vincent Mailhol