Re: [PATCH v4 10/11] can: lin: Support setting LIN mode

A LIN node can work as commander or responder, so introduce a new
control mode (CAN_CTRLMODE_LIN_COMMANDER) for configuration.

This enables e.g. the userland tool ip from iproute2 to turn on
commander mode when the device is being brought up.

Signed-off-by: Christoph Fritz <redacted>
---
 drivers/net/can/lin.c            | 40 +++++++++++++++++++++++++++++++-
 include/net/lin.h                |  7 ++++++
 include/uapi/linux/can/netlink.h |  1 +
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/lin.c b/drivers/net/can/lin.c
index f77abd7d7d21c..03ddf5d5a31b8 100644
--- a/drivers/net/can/lin.c
+++ b/drivers/net/can/lin.c

@@ -262,11 +262,40 @@ static netdev_tx_t lin_start_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 }
 
+static int lin_update_mode(struct net_device *ndev)
+{
+	struct lin_device *ldev = netdev_priv(ndev);
+	u32 ctrlmode = ldev->can.ctrlmode;
+	enum lin_mode lm;
+	int ret = 0;
+
+	lm = (ctrlmode & CAN_CTRLMODE_LIN_COMMANDER) ? LINBUS_COMMANDER :
+						       LINBUS_RESPONDER;
+	if (ldev->lmode != lm) {
+		if (!ldev->ldev_ops->update_lin_mode) {
+			netdev_err(ndev, "setting lin mode unsupported\n");

+			return ret;
+		}
+		ldev->lmode = lm;
+	}
+
+	return ret;
+}
+
 static int lin_open(struct net_device *ndev)
 {
 	struct lin_device *ldev = netdev_priv(ndev);
 	int ret;
 
+	ret = lin_update_mode(ndev);
+	if (ret)
+		return ret;
+
 	ldev->tx_busy = false;
 
 	ret = open_candev(ndev);

@@ -443,7 +472,7 @@ struct lin_device *register_lin(struct device *dev,
 	ndev->sysfs_groups[0] = &lin_sysfs_group;
 	ldev->can.bittiming.bitrate = LIN_DEFAULT_BAUDRATE;
 	ldev->can.ctrlmode = CAN_CTRLMODE_LIN;
-	ldev->can.ctrlmode_supported = 0;
+	ldev->can.ctrlmode_supported = CAN_CTRLMODE_LIN_COMMANDER;
 	ldev->can.bitrate_const = lin_bitrate;
 	ldev->can.bitrate_const_cnt = ARRAY_SIZE(lin_bitrate);
 	ldev->can.do_set_bittiming = lin_set_bittiming;

@@ -458,6 +487,15 @@ struct lin_device *register_lin(struct device *dev,
 		goto exit_candev;
 	}
 
+	ldev->lmode = LINBUS_RESPONDER;
+	if (ldev->ldev_ops->update_lin_mode) {
+		ret = ldev->ldev_ops->update_lin_mode(ldev, ldev->lmode);
+		if (ret) {
+			netdev_err(ndev, "updating lin mode failed\n");

+			goto exit_candev;
+		}
+	}
+
 	ret = register_candev(ndev);
 	if (ret)
 		goto exit_candev;

diff --git a/include/net/lin.h b/include/net/lin.h
index 31bb0feefd188..63ac870a0ab6f 100644
--- a/include/net/lin.h
+++ b/include/net/lin.h

@@ -36,6 +36,11 @@ struct lin_attr {
 	struct lin_device *ldev;
 };
 
+enum lin_mode {
+	LINBUS_RESPONDER = 0,
+	LINBUS_COMMANDER,
+};
+
 struct lin_device {
 	struct can_priv can;  /* must be the first member */
 	struct net_device *ndev;

@@ -45,6 +50,7 @@ struct lin_device {
 	struct work_struct tx_work;
 	bool tx_busy;
 	struct sk_buff *tx_skb;
+	enum lin_mode lmode;
 };
 
 enum lin_checksum_mode {

@@ -71,6 +77,7 @@ struct lin_device_ops {
 	int (*ldo_open)(struct lin_device *ldev);
 	int (*ldo_stop)(struct lin_device *ldev);
 	int (*ldo_tx)(struct lin_device *ldev, const struct lin_frame *frame);
+	int (*update_lin_mode)(struct lin_device *ldev, enum lin_mode lm);
 	int (*update_bitrate)(struct lin_device *ldev, u16 bitrate);
 	int (*update_responder_answer)(struct lin_device *ldev,
 				       const struct lin_responder_answer *answ);

diff --git a/include/uapi/linux/can/netlink.h b/include/uapi/linux/can/netlink.h
index a37f56d86c5f2..cc390f6444d59 100644
--- a/include/uapi/linux/can/netlink.h
+++ b/include/uapi/linux/can/netlink.h

@@ -104,6 +104,7 @@ struct can_ctrlmode {
 #define CAN_CTRLMODE_TDC_AUTO		0x200	/* CAN transiver automatically calculates TDCV */
 #define CAN_CTRLMODE_TDC_MANUAL		0x400	/* TDCV is manually set up by user */
 #define CAN_CTRLMODE_LIN		BIT(11)	/* LIN bus mode */
+#define CAN_CTRLMODE_LIN_COMMANDER	BIT(12)	/* LIN bus specific commander mode */
 
 /*
  * CAN device statistics