Hi Marc,

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+struct nct6694_can_priv {
+     struct can_priv can;    /* must be the first member */
+     struct net_device *ndev;
+     struct nct6694 *nct6694;
+     struct mutex lock;

What does lock protect?

The lock is used to protect tx_buf and rx_buf for each CAN device.

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+     struct sk_buff *tx_skb;
+     struct workqueue_struct *wq;
+     struct work_struct tx_work;
+     unsigned char *tx_buf;

void *

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+     unsigned char *rx_buf;

void *

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+     unsigned char can_idx;
+     bool tx_busy;

IMHO it makes no sense to have tx_skb and tx_busy

Okay! I will revisit these to evaluate whether they are still necessary.

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+};
+

I think there needs to be a tx_skb to record the skb passed by
start_xmit(), otherwise it can't handle the can_frame in tx_work. If
this is not necessary, could you please explain?
In addition, the tx flow is based on the implementation in
https://elixir.bootlin.com/linux/v6.12.6/source/drivers/net/can/spi/mcp251x.c

Thanks,
Ming