Le 10/12/2024 à 11:45, Ming Yu a écrit :

The Nuvoton NCT6694 is a peripheral expander with 16 GPIO chips,
6 I2C controllers, 2 CANfd controllers, 2 Watchdog timers, ADC,
PWM, and RTC.

This driver implements USB device functionality and shares the
chip's peripherals as a child device.

Each child device can use the USB functions nct6694_read_msg()
and nct6694_write_msg() to issue a command. They can also request
interrupt that will be called when the USB device receives its
interrupt pipe.

...

+int nct6694_read_msg(struct nct6694 *nct6694, u8 mod, u16 offset,
+		     u16 length, void *buf)
+{
+	struct nct6694_cmd_header *cmd_header = nct6694->cmd_header;
+	struct nct6694_response_header *response_header = nct6694->response_header;
+	struct usb_device *udev = nct6694->udev;
+	int tx_len, rx_len, ret;
+
+	guard(mutex)(&nct6694->access_lock);

Nitpick: This could be moved a few lines below, should it still comply 
with your coding style.

+
+	/* Send command packet to USB device */
+	cmd_header->mod = mod;
+	cmd_header->cmd = offset & 0xFF;
+	cmd_header->sel = (offset >> 8) & 0xFF;
+	cmd_header->hctrl = NCT6694_HCTRL_GET;
+	cmd_header->len = length;
+
+	ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, NCT6694_BULK_OUT_EP),
+			   cmd_header, NCT6694_CMD_PACKET_SZ, &tx_len,
+			   nct6694->timeout);
+	if (ret)
+		return ret;
+
+	/* Receive response packet from USB device */
+	ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, NCT6694_BULK_IN_EP),
+			   response_header, NCT6694_CMD_PACKET_SZ, &rx_len,
+			   nct6694->timeout);
+	if (ret)
+		return ret;
+
+	ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, NCT6694_BULK_IN_EP),
+			   buf, NCT6694_MAX_PACKET_SZ, &rx_len, nct6694->timeout);
+	if (ret)
+		return ret;
+
+	return nct6694_response_err_handling(nct6694, response_header->sts);
+}
+EXPORT_SYMBOL(nct6694_read_msg);
+
+int nct6694_write_msg(struct nct6694 *nct6694, u8 mod, u16 offset,
+		      u16 length, void *buf)
+{
+	struct nct6694_cmd_header *cmd_header = nct6694->cmd_header;
+	struct nct6694_response_header *response_header = nct6694->response_header;
+	struct usb_device *udev = nct6694->udev;
+	int tx_len, rx_len, ret;
+
+	guard(mutex)(&nct6694->access_lock);

Nitpick: This could be moved a few lines below, should it still comply 
with your coding style.

+
+	/* Send command packet to USB device  */

Nitpick: double space before */

+	cmd_header->mod = mod;
+	cmd_header->cmd = offset & 0xFF;
+	cmd_header->sel = (offset >> 8) & 0xFF;
+	cmd_header->hctrl = NCT6694_HCTRL_SET;
+	cmd_header->len = length;

...

+static struct irq_chip nct6694_irq_chip = {

const?

+	.name = "nct6694-irq",
+	.flags = IRQCHIP_SKIP_SET_WAKE,
+	.irq_bus_lock = nct6694_irq_lock,
+	.irq_bus_sync_unlock = nct6694_irq_sync_unlock,
+	.irq_enable = nct6694_irq_enable,
+	.irq_disable = nct6694_irq_disable,
+};

...

+static int nct6694_usb_probe(struct usb_interface *iface,
+			     const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(iface);
+	struct device *dev = &udev->dev;
+	struct usb_host_interface *interface;
+	struct usb_endpoint_descriptor *int_endpoint;
+	struct nct6694 *nct6694;
+	struct nct6694_cmd_header *cmd_header;
+	struct nct6694_response_header *response_header;
+	int pipe, maxp;
+	int ret;
+
+	interface = iface->cur_altsetting;
+
+	int_endpoint = &interface->endpoint[0].desc;
+	if (!usb_endpoint_is_int_in(int_endpoint))
+		return -ENODEV;
+
+	nct6694 = devm_kzalloc(dev, sizeof(*nct6694), GFP_KERNEL);
+	if (!nct6694)
+		return -ENOMEM;
+
+	pipe = usb_rcvintpipe(udev, NCT6694_INT_IN_EP);
+	maxp = usb_maxpacket(udev, pipe);
+
+	cmd_header = devm_kzalloc(dev, sizeof(*cmd_header),
+				  GFP_KERNEL);
+	if (!cmd_header)
+		return -ENOMEM;
+
+	response_header = devm_kzalloc(dev, sizeof(*response_header),
+				       GFP_KERNEL);
+	if (!response_header)
+		return -ENOMEM;
+
+	nct6694->int_buffer = devm_kcalloc(dev, NCT6694_MAX_PACKET_SZ,
+					   sizeof(unsigned char), GFP_KERNEL);

Why for cmd_header and response_header we use a temp variable, while 
here we update directly nct6694->int_buffer?

It would save a few LoC do remove this temp var.

+	if (!nct6694->int_buffer)
+		return -ENOMEM;
+
+	nct6694->int_in_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!nct6694->int_in_urb)
+		return -ENOMEM;

...

CJ