Marc Kleine-Budde [off-list ref] 於 2025年3月27日 週四 上午1:35寫道：

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+static int nct6694_can_start(struct net_device *ndev)
+{
+     struct nct6694_can_priv *priv = netdev_priv(ndev);
+     const struct can_bittiming *d_bt = &priv->can.data_bittiming;
+     const struct can_bittiming *n_bt = &priv->can.bittiming;
+     struct nct6694_can_setting *setting __free(kfree) = NULL;
+     const struct nct6694_cmd_header cmd_hd = {
+             .mod = NCT6694_CAN_MOD,
+             .cmd = NCT6694_CAN_SETTING,
+             .sel = ndev->dev_port,
+             .len = cpu_to_le16(sizeof(*setting))
+     };
+     int ret;
+
+     setting = kzalloc(sizeof(*setting), GFP_KERNEL);
+     if (!setting)
+             return -ENOMEM;
+
+     setting->nbr = cpu_to_le32(n_bt->bitrate);
+     setting->dbr = cpu_to_le32(d_bt->bitrate);

I just noticed one thing that needs clarification/documentation.

You have nct6694_can_bittiming_nominal_const and
nct6694_can_bittiming_data_const, but only pass the bit rates to your
device.

Do the bit timing const really reflect the HW limitations of your
device?

Are you sure your device uses the same algorithm as the kernel and
calculates the same bit timing parameters as the kernel, so that the
values given to the user space reflects the bit timing parameter chosen
by your device?

Originally, I only intended to provide NBR and DBR for user
configuration. In the next patch, I will add code to configure
NBTP(Nominal Bit Timing Prescaler) and DBTP(Data Bit Timing Prescaler)
based on the setting of nct6694_can_bittiming_nominal_const and
nct6694_can_bittiming_data_const.

Sounds good, but this doesn't answer my questions:

You have nct6694_can_bittiming_nominal_const and
nct6694_can_bittiming_data_const, but only pass the bit rates and the
prescaler to your device.

I understand.
The prescaler field is used to calculate sjw, brp, prop_seg,
phase_seg1 and phase_seg2. I will update the code in the next patch.


Thanks,
Ming