Subject: Re: [PATCH v2 02/12] HID: hexLIN: Add support for USB LIN bus adapter

From: Simon Horman <[email-masked]>
Date: Sat, 4 May 2024 13:58:28 +0100

On Thu, May 02, 2024 at 09:55:24AM +0200, Christoph Fritz wrote:
> This patch introduces driver support for the hexLIN USB LIN bus adapter,
> enabling LIN communication over USB for both controller and responder
> modes. The driver interfaces with the CAN_LIN framework for userland
> connectivity.
> 
> For more details on the adapter, visit: https://hexdev.de/hexlin/
> 
> Tested-by: Andreas Lauser <[email-masked]>
> Signed-off-by: Christoph Fritz <[email-masked]>

Hi Christoph,

Some minor feedback from my side.

...

> diff --git a/drivers/hid/hid-hexdev-hexlin.c b/drivers/hid/hid-hexdev-hexlin.c

...

> +static int hexlin_queue_frames_insert(struct hexlin_priv_data *priv,
> +				      const u8 *raw_data, int sz)
> +{
> +	struct hid_device *hdev = priv->hid_dev;
> +	struct hexlin_frame hxf;
> +	struct lin_frame lf;
> +
> +	if (sz != sizeof(struct hexlin_frame))
> +		return -EREMOTEIO;
> +
> +	memcpy(&hxf, raw_data, sz);
> +	le32_to_cpus(hxf.flags);
> +
> +	lf.len = hxf.len;
> +	lf.lin_id = hxf.lin_id;
> +	memcpy(lf.data, hxf.data, LIN_MAX_DLEN);
> +	lf.checksum = hxf.checksum;
> +	lf.checksum_mode = hxf.checksum_mode;
> +
> +	hid_dbg(hdev, "id:%02x, len:%u, data:%*ph, checksum:%02x (%s)\n",
> +		   lf.lin_id, lf.len, lf.len, lf.data, lf.checksum,
> +		   lf.checksum_mode ? "enhanced" : "classic");

nit: The indentation above is not quite right.
     It should align to inside the opening '(' like this.

	hid_dbg(hdev, "id:%02x, len:%u, data:%*ph, checksum:%02x (%s)\n",
		lf.lin_id, lf.len, lf.len, lf.data, lf.checksum,
		lf.checksum_mode ? "enhanced" : "classic");

Flagged by checkpatch.

...

> +static int hexlin_set_baudrate(struct hexlin_priv_data *priv, u16 baudrate)
> +{
> +	struct hexlin_baudrate_req req;
> +	int ret;
> +
> +	if (baudrate < LIN_MIN_BAUDRATE || baudrate > LIN_MAX_BAUDRATE)
> +		return -EINVAL;
> +
> +	req.cmd = HEXLIN_SET_BAUDRATE;
> +	req.baudrate = cpu_to_le16(baudrate);

The type of req.baudrate is u16, a host byte-order type.
But it is being assigned a little endian value.
This does not seem right.

Flagged by Smatch.

> +
> +	ret = hexlin_tx_req_status(priv, &req,
> +				   sizeof(struct hexlin_baudrate_req));
> +	if (ret)
> +		hid_err(priv->hid_dev, "%s failed with %d\n", __func__, ret);
> +
> +	return ret;
> +}

...

> +static int hexlin_probe(struct hid_device *hdev,
> +			const struct hid_device_id *id)
> +{
> +	struct hexlin_priv_data *priv;
> +	int ret;
> +
> +	priv = devm_kzalloc(&hdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->hid_dev = hdev;
> +	hid_set_drvdata(hdev, priv);
> +
> +	mutex_init(&priv->tx_lock);
> +
> +	ret = hid_parse(hdev);
> +	if (ret) {
> +		hid_err(hdev, "hid parse failed with %d\n", ret);
> +		goto fail_and_free;
> +	}
> +
> +	ret = hid_hw_start(hdev, HID_CONNECT_DRIVER);
> +	if (ret) {
> +		hid_err(hdev, "hid hw start failed with %d\n", ret);
> +		goto fail_and_stop;
> +	}
> +
> +	ret = hid_hw_open(hdev);
> +	if (ret) {
> +		hid_err(hdev, "hid hw open failed with %d\n", ret);
> +		goto fail_and_close;
> +	}
> +
> +	init_completion(&priv->wait_in_report);
> +
> +	hid_device_io_start(hdev);
> +
> +	ret = init_hw(priv);
> +	if (ret)
> +		goto fail_and_close;
> +
> +	priv->ldev = register_lin(&hdev->dev, &hexlin_ldo);
> +	if (IS_ERR_OR_NULL(priv->ldev)) {
> +		ret = PTR_ERR(priv->ldev);
> +		goto fail_and_close;

Is it intentional that when priv->ldev is NULL here,
the function will return 0?

Flagged by Smatch.

> +	}
> +
> +	hid_hw_close(hdev);
> +
> +	hid_info(hdev, "hexLIN (fw-version: %u) probed\n", priv->fw_version);
> +
> +	return 0;
> +
> +fail_and_close:
> +	hid_hw_close(hdev);
> +fail_and_stop:
> +	hid_hw_stop(hdev);
> +fail_and_free:
> +	mutex_destroy(&priv->tx_lock);
> +	return ret;
> +}

...