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.

Signed-off-by: Ming Yu <tmyu0@nuvoton.com>
---
 MAINTAINERS                 |   7 +
 drivers/mfd/Kconfig         |  10 +
 drivers/mfd/Makefile        |   2 +
 drivers/mfd/nct6694.c       | 382 ++++++++++++++++++++++++++++++++++++
 include/linux/mfd/nct6694.h | 139 +++++++++++++
 5 files changed, 540 insertions(+)
 create mode 100644 drivers/mfd/nct6694.c
 create mode 100644 include/linux/mfd/nct6694.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 67d2159406c2..9c9a94ff8f98 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16541,6 +16541,13 @@ F:	drivers/nubus/
 F:	include/linux/nubus.h
 F:	include/uapi/linux/nubus.h
 
+NUVOTON NCT6694 MFD DRIVER
+M:	Ming Yu <tmyu0@nuvoton.com>
+L:	linux-kernel@vger.kernel.org
+S:	Supported
+F:	drivers/mfd/nct6694.c
+F:	include/linux/mfd/nct6694.h
+
 NVIDIA (rivafb and nvidiafb) FRAMEBUFFER DRIVER
 M:	Antonino Daplas <adaplas@gmail.com>
 L:	linux-fbdev@vger.kernel.org
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 03c1e4e3eea4..07ccc32f9985 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -558,6 +558,16 @@ config MFD_MX25_TSADC
 	  i.MX25 processors. They consist of a conversion queue for general
 	  purpose ADC and a queue for Touchscreens.
 
+config MFD_NCT6694
+	tristate "Nuvoton NCT6694 support"
+	select MFD_CORE
+	depends on USB
+	help
+	  This adds support for Nuvoton USB device NCT6694 sharing peripherals
+	  This includes the USB devcie driver and core APIs.
+	  Additional drivers must be enabled in order to use the functionality
+	  of the device.
+
 config MFD_HI6421_PMIC
 	tristate "HiSilicon Hi6421 PMU/Codec IC"
 	depends on OF
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index e057d6d6faef..9d0365ba6a26 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -117,6 +117,8 @@ obj-$(CONFIG_TWL6040_CORE)	+= twl6040.o
 
 obj-$(CONFIG_MFD_MX25_TSADC)	+= fsl-imx25-tsadc.o
 
+obj-$(CONFIG_MFD_NCT6694)	+= nct6694.o
+
 obj-$(CONFIG_MFD_MC13XXX)	+= mc13xxx-core.o
 obj-$(CONFIG_MFD_MC13XXX_SPI)	+= mc13xxx-spi.o
 obj-$(CONFIG_MFD_MC13XXX_I2C)	+= mc13xxx-i2c.o
diff --git a/drivers/mfd/nct6694.c b/drivers/mfd/nct6694.c
new file mode 100644
index 000000000000..071333d13eae
--- /dev/null
+++ b/drivers/mfd/nct6694.c
@@ -0,0 +1,382 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 MFD driver based on USB interface.
+ *
+ * Copyright (C) 2024 Nuvoton Technology Corp.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/nct6694.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+
+#define MFD_DEV_SIMPLE(_name)				\
+{							\
+	.name = NCT6694_DEV_##_name,			\
+}							\
+
+#define MFD_DEV_WITH_ID(_name, _id)			\
+{							\
+	.name = NCT6694_DEV_##_name,			\
+	.id = _id,					\
+}
+
+/* MFD device resources */
+static const struct mfd_cell nct6694_dev[] = {
+	MFD_DEV_WITH_ID(GPIO, 0x0),
+	MFD_DEV_WITH_ID(GPIO, 0x1),
+	MFD_DEV_WITH_ID(GPIO, 0x2),
+	MFD_DEV_WITH_ID(GPIO, 0x3),
+	MFD_DEV_WITH_ID(GPIO, 0x4),
+	MFD_DEV_WITH_ID(GPIO, 0x5),
+	MFD_DEV_WITH_ID(GPIO, 0x6),
+	MFD_DEV_WITH_ID(GPIO, 0x7),
+	MFD_DEV_WITH_ID(GPIO, 0x8),
+	MFD_DEV_WITH_ID(GPIO, 0x9),
+	MFD_DEV_WITH_ID(GPIO, 0xA),
+	MFD_DEV_WITH_ID(GPIO, 0xB),
+	MFD_DEV_WITH_ID(GPIO, 0xC),
+	MFD_DEV_WITH_ID(GPIO, 0xD),
+	MFD_DEV_WITH_ID(GPIO, 0xE),
+	MFD_DEV_WITH_ID(GPIO, 0xF),
+
+	MFD_DEV_WITH_ID(I2C, 0x0),
+	MFD_DEV_WITH_ID(I2C, 0x1),
+	MFD_DEV_WITH_ID(I2C, 0x2),
+	MFD_DEV_WITH_ID(I2C, 0x3),
+	MFD_DEV_WITH_ID(I2C, 0x4),
+	MFD_DEV_WITH_ID(I2C, 0x5),
+
+	MFD_DEV_WITH_ID(CAN, 0x0),
+	MFD_DEV_WITH_ID(CAN, 0x1),
+
+	MFD_DEV_WITH_ID(WDT, 0x0),
+	MFD_DEV_WITH_ID(WDT, 0x1),
+
+	MFD_DEV_SIMPLE(HWMON),
+	MFD_DEV_SIMPLE(RTC),
+};
+
+static int nct6694_response_err_handling(struct nct6694 *nct6694,
+					 unsigned char err_status)
+{
+	struct device *dev = &nct6694->udev->dev;
+
+	switch (err_status) {
+	case NCT6694_NO_ERROR:
+		return err_status;
+	case NCT6694_NOT_SUPPORT_ERROR:
+		dev_dbg(dev, "%s: Command is not support!\n", __func__);
+		break;
+	case NCT6694_NO_RESPONSE_ERROR:
+		dev_dbg(dev, "%s: Command is no response!\n", __func__);
+		break;
+	case NCT6694_TIMEOUT_ERROR:
+		dev_dbg(dev, "%s: Command is timeout!\n", __func__);
+		break;
+	case NCT6694_PENDING:
+		dev_dbg(dev, "%s: Command is pending!\n", __func__);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return -EIO;
+}
+
+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);
+
+	/* 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);
+
+	/* 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_SET;
+	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;
+
+	ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, NCT6694_BULK_OUT_EP),
+			   buf, length, &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_write_msg);
+
+static void usb_int_callback(struct urb *urb)
+{
+	struct nct6694 *nct6694 = urb->context;
+	struct device *dev = &nct6694->udev->dev;
+	unsigned int *int_status = urb->transfer_buffer;
+	int ret;
+
+	switch (urb->status) {
+	case 0:
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		return;
+	default:
+		goto resubmit;
+	}
+
+	while (*int_status) {
+		int irq = __ffs(*int_status);
+
+		if (*int_status & (1 << irq))
+			generic_handle_irq_safe(irq_find_mapping(nct6694->domain, irq));
+
+		*int_status &= ~(1 << irq);
+	}
+
+resubmit:
+	ret = usb_submit_urb(urb, GFP_ATOMIC);
+	if (ret)
+		dev_dbg(dev, "%s: Failed to resubmit urb, status %d",
+			__func__, ret);
+}
+
+static void nct6694_irq_lock(struct irq_data *data)
+{
+	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
+
+	mutex_lock(&nct6694->irq_lock);
+}
+
+static void nct6694_irq_sync_unlock(struct irq_data *data)
+{
+	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
+
+	mutex_unlock(&nct6694->irq_lock);
+}
+
+static void nct6694_irq_enable(struct irq_data *data)
+{
+	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
+	unsigned int irq = data->hwirq;
+
+	nct6694->irq_enable |= (1 << irq);
+}
+
+static void nct6694_irq_disable(struct irq_data *data)
+{
+	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
+	unsigned int irq = data->hwirq;
+
+	nct6694->irq_enable &= ~(1 << irq);
+}
+
+static struct irq_chip nct6694_irq_chip = {
+	.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_irq_domain_map(struct irq_domain *d, unsigned int irq,
+				  irq_hw_number_t hw)
+{
+	struct nct6694 *nct6694 = d->host_data;
+
+	irq_set_chip_data(irq, nct6694);
+	irq_set_chip_and_handler(irq, &nct6694_irq_chip, handle_simple_irq);
+
+	return 0;
+}
+
+static void nct6694_irq_domain_unmap(struct irq_domain *d, unsigned int irq)
+{
+	irq_set_chip_and_handler(irq, NULL, NULL);
+	irq_set_chip_data(irq, NULL);
+}
+
+static const struct irq_domain_ops nct6694_irq_domain_ops = {
+	.map	= nct6694_irq_domain_map,
+	.unmap	= nct6694_irq_domain_unmap,
+};
+
+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);
+	if (!nct6694->int_buffer)
+		return -ENOMEM;
+
+	nct6694->int_in_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!nct6694->int_in_urb)
+		return -ENOMEM;
+
+	nct6694->domain = irq_domain_add_simple(NULL, NCT6694_NR_IRQS, 0,
+						&nct6694_irq_domain_ops,
+						nct6694);
+	if (!nct6694->domain)
+		return -ENODEV;
+
+	nct6694->udev = udev;
+	nct6694->timeout = NCT6694_URB_TIMEOUT;	/* Wait until urb complete */
+	nct6694->cmd_header = cmd_header;
+	nct6694->response_header = response_header;
+
+	mutex_init(&nct6694->access_lock);
+	mutex_init(&nct6694->irq_lock);
+
+	usb_fill_int_urb(nct6694->int_in_urb, udev, pipe,
+			 nct6694->int_buffer, maxp, usb_int_callback,
+			 nct6694, int_endpoint->bInterval);
+	ret = usb_submit_urb(nct6694->int_in_urb, GFP_KERNEL);
+	if (ret)
+		goto err_urb;
+
+	dev_set_drvdata(dev, nct6694);
+	usb_set_intfdata(iface, nct6694);
+
+	ret = mfd_add_hotplug_devices(dev, nct6694_dev, ARRAY_SIZE(nct6694_dev));
+	if (ret)
+		goto err_mfd;
+
+	dev_info(dev, "Probed device: (%04X:%04X)\n", id->idVendor, id->idProduct);
+	return 0;
+
+err_mfd:
+	usb_kill_urb(nct6694->int_in_urb);
+err_urb:
+	usb_free_urb(nct6694->int_in_urb);
+	return dev_err_probe(dev, ret, "Probe failed\n");
+}
+
+static void nct6694_usb_disconnect(struct usb_interface *iface)
+{
+	struct usb_device *udev = interface_to_usbdev(iface);
+	struct nct6694 *nct6694 = usb_get_intfdata(iface);
+
+	mfd_remove_devices(&udev->dev);
+	usb_kill_urb(nct6694->int_in_urb);
+	usb_free_urb(nct6694->int_in_urb);
+}
+
+static const struct usb_device_id nct6694_ids[] = {
+	{ USB_DEVICE_AND_INTERFACE_INFO(NCT6694_VENDOR_ID,
+					NCT6694_PRODUCT_ID,
+					0xFF, 0x00, 0x00)},
+	{}
+};
+MODULE_DEVICE_TABLE(usb, nct6694_ids);
+
+static struct usb_driver nct6694_usb_driver = {
+	.name	= "nct6694",
+	.id_table = nct6694_ids,
+	.probe = nct6694_usb_probe,
+	.disconnect = nct6694_usb_disconnect,
+};
+
+module_usb_driver(nct6694_usb_driver);
+
+MODULE_DESCRIPTION("USB-MFD driver for NCT6694");
+MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/mfd/nct6694.h b/include/linux/mfd/nct6694.h
new file mode 100644
index 000000000000..9733d47f5a01
--- /dev/null
+++ b/include/linux/mfd/nct6694.h
@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Nuvoton NCT6694 USB transaction and data structure.
+ *
+ * Copyright (C) 2024 Nuvoton Technology Corp.
+ */
+
+#ifndef __MFD_NCT6694_H
+#define __MFD_NCT6694_H
+
+#define NCT6694_DEV_GPIO	"nct6694-gpio"
+#define NCT6694_DEV_I2C		"nct6694-i2c"
+#define NCT6694_DEV_CAN		"nct6694-can"
+#define NCT6694_DEV_WDT		"nct6694-wdt"
+#define NCT6694_DEV_HWMON	"nct6694-hwmon"
+#define NCT6694_DEV_RTC		"nct6694-rtc"
+
+#define NCT6694_VENDOR_ID	0x0416
+#define NCT6694_PRODUCT_ID	0x200B
+#define NCT6694_INT_IN_EP	0x81
+#define NCT6694_BULK_IN_EP	0x02
+#define NCT6694_BULK_OUT_EP	0x03
+#define NCT6694_MAX_PACKET_SZ	0x200
+
+#define NCT6694_CMD_PACKET_SZ	0x8
+#define NCT6694_HCTRL_SET	0x40
+#define NCT6694_HCTRL_GET	0x80
+
+#define NCT6694_URB_TIMEOUT	1000
+
+enum nct6694_irq_id {
+	NCT6694_IRQ_GPIO0 = 0,
+	NCT6694_IRQ_GPIO1,
+	NCT6694_IRQ_GPIO2,
+	NCT6694_IRQ_GPIO3,
+	NCT6694_IRQ_GPIO4,
+	NCT6694_IRQ_GPIO5,
+	NCT6694_IRQ_GPIO6,
+	NCT6694_IRQ_GPIO7,
+	NCT6694_IRQ_GPIO8,
+	NCT6694_IRQ_GPIO9,
+	NCT6694_IRQ_GPIOA,
+	NCT6694_IRQ_GPIOB,
+	NCT6694_IRQ_GPIOC,
+	NCT6694_IRQ_GPIOD,
+	NCT6694_IRQ_GPIOE,
+	NCT6694_IRQ_GPIOF,
+	NCT6694_IRQ_CAN1,
+	NCT6694_IRQ_CAN2,
+	NCT6694_IRQ_RTC,
+	NCT6694_NR_IRQS,
+};
+
+enum nct6694_response_err_status {
+	NCT6694_NO_ERROR = 0,
+	NCT6694_FORMAT_ERROR,
+	NCT6694_RESERVED1,
+	NCT6694_RESERVED2,
+	NCT6694_NOT_SUPPORT_ERROR,
+	NCT6694_NO_RESPONSE_ERROR,
+	NCT6694_TIMEOUT_ERROR,
+	NCT6694_PENDING,
+};
+
+struct nct6694 {
+	struct usb_device *udev;
+	struct urb *int_in_urb;
+	struct irq_domain *domain;
+	struct nct6694_cmd_header *cmd_header;
+	struct nct6694_response_header *response_header;
+	struct mutex access_lock;
+	struct mutex irq_lock;
+	unsigned char *int_buffer;
+	unsigned int irq_enable;
+	/* time in msec to wait for the urb to the complete */
+	long timeout;
+};
+
+struct nct6694_cmd_header {
+	unsigned char rsv1;
+	unsigned char mod;
+	unsigned char cmd;
+	unsigned char sel;
+	unsigned char hctrl;
+	unsigned char rsv2;
+	unsigned short len;
+} __packed;
+
+struct nct6694_response_header {
+	unsigned char sequence_id;
+	unsigned char sts;
+	unsigned int rsv;
+	unsigned short len;
+} __packed;
+
+/*
+ * nct6694_read_msg - Receive data from NCT6694 USB device
+ *
+ * @nct6694 - Nuvoton NCT6694 structure
+ * @mod - Module byte
+ * @offset - Offset byte or (Select byte | Command byte)
+ * @length - Length byte
+ * @buf - Read data from rx buffer
+ *
+ * USB Transaction format:
+ *
+ *	OUT	|RSV|MOD|CMD|SEL|HCTL|RSV|LEN_L|LEN_H|
+ *	OUT	|SEQ|STS|RSV|RSV|RSV|RSV||LEN_L|LEN_H|
+ *	IN	|-------D------A------D------A-------|
+ *	IN			......
+ *	IN	|-------D------A------D------A-------|
+ */
+int nct6694_read_msg(struct nct6694 *nct6694, u8 mod, u16 offset,
+		     u16 length, void *buf);
+
+/*
+ * nct6694_read_msg - Transmit data to NCT6694 USB device
+ *
+ * @nct6694 - Nuvoton NCT6694 structure
+ * @mod - Module byte
+ * @offset - Offset byte or (Select byte | Command byte)
+ * @length - Length byte
+ * @buf - Write data to tx buffer
+ *
+ * USB Transaction format:
+ *
+ *	OUT	|RSV|MOD|CMD|SEL|HCTL|RSV|LEN_L|LEN_H|
+ *	OUT	|-------D------A------D------A-------|
+ *	OUT			......
+ *	OUT	|-------D------A------D------A-------|
+ *	IN	|SEQ|STS|RSV|RSV|RSV|RSV||LEN_L|LEN_H|
+ *	IN	|-------D------A------D------A-------|
+ *	IN			......
+ *	IN	|-------D------A------D------A-------|
+ */
+int nct6694_write_msg(struct nct6694 *nct6694, u8 mod, u16 offset,
+		      u16 length, void *buf);
+
+#endif
-- 
2.34.1

Hi Ming,

thanks for your patch!

On Tue, Dec 10, 2024 at 11:45 AM Ming Yu <a0282524688@gmail.com> wrote:

> 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.
>
> Signed-off-by: Ming Yu <tmyu0@nuvoton.com>
(...)
> +       while (*int_status) {
> +               int irq = __ffs(*int_status);
> +
> +               if (*int_status & (1 << irq))
> +                       generic_handle_irq_safe(irq_find_mapping(nct6694->domain, irq));
> +
> +               *int_status &= ~(1 << irq);

What about doing what you do in the GPIO driver and
#include <linux/bits.h>

And search and replace "(1 << irq)" with BIT(irq)?

PS the main reason we do this is because

int a = (1 << 31);

becomes a negative number on 32bit machines, and
can lead to confusing side effects. BIT() always work
on unsigned.

Yours,
Linus Walleij

Dear Linus,

Thank you for your reply,

Linus Walleij <linus.walleij@linaro.org> 於 2024年12月20日 週五 下午8:45寫道：
>
> Hi Ming,
>
> thanks for your patch!
>
...
> > +       while (*int_status) {
> > +               int irq = __ffs(*int_status);
> > +
> > +               if (*int_status & (1 << irq))
> > +                       generic_handle_irq_safe(irq_find_mapping(nct6694->domain, irq));
> > +
> > +               *int_status &= ~(1 << irq);
>
> What about doing what you do in the GPIO driver and
> #include <linux/bits.h>
>
> And search and replace "(1 << irq)" with BIT(irq)?
>
> PS the main reason we do this is because
>
> int a = (1 << 31);
>
> becomes a negative number on 32bit machines, and
> can lead to confusing side effects. BIT() always work
> on unsigned.
>

Understood! I will make the modifications in the v4.

Best regards,
Ming

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

On 10/12/2024 11:45, Ming Yu wrote:
> +	nct6694->int_buffer = devm_kcalloc(dev, NCT6694_MAX_PACKET_SZ,
> +					   sizeof(unsigned char), GFP_KERNEL);
> +	if (!nct6694->int_buffer)
> +		return -ENOMEM;
> +
> +	nct6694->int_in_urb = usb_alloc_urb(0, GFP_KERNEL);
> +	if (!nct6694->int_in_urb)
> +		return -ENOMEM;
> +
> +	nct6694->domain = irq_domain_add_simple(NULL, NCT6694_NR_IRQS, 0,
> +						&nct6694_irq_domain_ops,
> +						nct6694);
> +	if (!nct6694->domain)
> +		return -ENODEV;
> +
> +	nct6694->udev = udev;
> +	nct6694->timeout = NCT6694_URB_TIMEOUT;	/* Wait until urb complete */
> +	nct6694->cmd_header = cmd_header;
> +	nct6694->response_header = response_header;
> +
> +	mutex_init(&nct6694->access_lock);
> +	mutex_init(&nct6694->irq_lock);
> +
> +	usb_fill_int_urb(nct6694->int_in_urb, udev, pipe,
> +			 nct6694->int_buffer, maxp, usb_int_callback,
> +			 nct6694, int_endpoint->bInterval);
> +	ret = usb_submit_urb(nct6694->int_in_urb, GFP_KERNEL);
> +	if (ret)
> +		goto err_urb;
> +
> +	dev_set_drvdata(dev, nct6694);
> +	usb_set_intfdata(iface, nct6694);
> +
> +	ret = mfd_add_hotplug_devices(dev, nct6694_dev, ARRAY_SIZE(nct6694_dev));
> +	if (ret)
> +		goto err_mfd;
> +
> +	dev_info(dev, "Probed device: (%04X:%04X)\n", id->idVendor, id->idProduct);

Drop. Duplicating existing messages and interfaces. Your driver is
supposed to be silent on success.

> +	return 0;
> +
> +err_mfd:
> +	usb_kill_urb(nct6694->int_in_urb);
> +err_urb:
> +	usb_free_urb(nct6694->int_in_urb);
> +	return dev_err_probe(dev, ret, "Probe failed\n");

No, this should go to individual call causing errors so this will be
informative. Above is not informative at all and kernel already reports
this, so drop.

> +}
> +
> +static void nct6694_usb_disconnect(struct usb_interface *iface)
> +{
> +	struct usb_device *udev = interface_to_usbdev(iface);
> +	struct nct6694 *nct6694 = usb_get_intfdata(iface);


Best regards,
Krzysztof

Dear Krzysztof,

Thank you for your comments,

Krzysztof Kozlowski <krzk@kernel.org> 於 2024年12月10日 週二 下午10:38寫道：
>
> > +
> > +     dev_set_drvdata(dev, nct6694);
> > +     usb_set_intfdata(iface, nct6694);
> > +
> > +     ret = mfd_add_hotplug_devices(dev, nct6694_dev, ARRAY_SIZE(nct6694_dev));
> > +     if (ret)
> > +             goto err_mfd;
> > +
> > +     dev_info(dev, "Probed device: (%04X:%04X)\n", id->idVendor, id->idProduct);
>
> Drop. Duplicating existing messages and interfaces. Your driver is
> supposed to be silent on success.
>

Okay, I will drop it in v4.

> > +     return 0;
> > +
> > +err_mfd:
> > +     usb_kill_urb(nct6694->int_in_urb);
> > +err_urb:
> > +     usb_free_urb(nct6694->int_in_urb);
> > +     return dev_err_probe(dev, ret, "Probe failed\n");
>
> No, this should go to individual call causing errors so this will be
> informative. Above is not informative at all and kernel already reports
> this, so drop.
>

Okay, I will drop it in v4.

> > +}
> > +
> > +static void nct6694_usb_disconnect(struct usb_interface *iface)
> > +{
> > +     struct usb_device *udev = interface_to_usbdev(iface);
> > +     struct nct6694 *nct6694 = usb_get_intfdata(iface);
>

Best regards,
Ming

On 12/10/2024 11:45 AM, Ming Yu wrote:
> 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.
> 
> Signed-off-by: Ming Yu <tmyu0@nuvoton.com>
> ---
>   MAINTAINERS                 |   7 +
>   drivers/mfd/Kconfig         |  10 +
>   drivers/mfd/Makefile        |   2 +
>   drivers/mfd/nct6694.c       | 382 ++++++++++++++++++++++++++++++++++++
>   include/linux/mfd/nct6694.h | 139 +++++++++++++
>   5 files changed, 540 insertions(+)
>   create mode 100644 drivers/mfd/nct6694.c
>   create mode 100644 include/linux/mfd/nct6694.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 67d2159406c2..9c9a94ff8f98 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -16541,6 +16541,13 @@ F:	drivers/nubus/
>   F:	include/linux/nubus.h
>   F:	include/uapi/linux/nubus.h
>   
> +NUVOTON NCT6694 MFD DRIVER
> +M:	Ming Yu <tmyu0@nuvoton.com>
> +L:	linux-kernel@vger.kernel.org
> +S:	Supported
> +F:	drivers/mfd/nct6694.c
> +F:	include/linux/mfd/nct6694.h
> +
>   NVIDIA (rivafb and nvidiafb) FRAMEBUFFER DRIVER
>   M:	Antonino Daplas <adaplas@gmail.com>
>   L:	linux-fbdev@vger.kernel.org
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 03c1e4e3eea4..07ccc32f9985 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -558,6 +558,16 @@ config MFD_MX25_TSADC
>   	  i.MX25 processors. They consist of a conversion queue for general
>   	  purpose ADC and a queue for Touchscreens.
>   
> +config MFD_NCT6694
> +	tristate "Nuvoton NCT6694 support"
> +	select MFD_CORE
> +	depends on USB
> +	help
> +	  This adds support for Nuvoton USB device NCT6694 sharing peripherals
> +	  This includes the USB devcie driver and core APIs.
> +	  Additional drivers must be enabled in order to use the functionality
> +	  of the device.
> +
>   config MFD_HI6421_PMIC
>   	tristate "HiSilicon Hi6421 PMU/Codec IC"
>   	depends on OF
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index e057d6d6faef..9d0365ba6a26 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -117,6 +117,8 @@ obj-$(CONFIG_TWL6040_CORE)	+= twl6040.o
>   
>   obj-$(CONFIG_MFD_MX25_TSADC)	+= fsl-imx25-tsadc.o
>   
> +obj-$(CONFIG_MFD_NCT6694)	+= nct6694.o
> +
>   obj-$(CONFIG_MFD_MC13XXX)	+= mc13xxx-core.o
>   obj-$(CONFIG_MFD_MC13XXX_SPI)	+= mc13xxx-spi.o
>   obj-$(CONFIG_MFD_MC13XXX_I2C)	+= mc13xxx-i2c.o
> diff --git a/drivers/mfd/nct6694.c b/drivers/mfd/nct6694.c
> new file mode 100644
> index 000000000000..071333d13eae
> --- /dev/null
> +++ b/drivers/mfd/nct6694.c
> @@ -0,0 +1,382 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Nuvoton NCT6694 MFD driver based on USB interface.
> + *
> + * Copyright (C) 2024 Nuvoton Technology Corp.
> + */
> +
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/irqdomain.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mfd/nct6694.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/usb.h>
> +
> +#define MFD_DEV_SIMPLE(_name)				\
> +{							\
> +	.name = NCT6694_DEV_##_name,			\
> +}							\
> +
> +#define MFD_DEV_WITH_ID(_name, _id)			\
> +{							\
> +	.name = NCT6694_DEV_##_name,			\
> +	.id = _id,					\
> +}
> +
> +/* MFD device resources */
> +static const struct mfd_cell nct6694_dev[] = {
> +	MFD_DEV_WITH_ID(GPIO, 0x0),
> +	MFD_DEV_WITH_ID(GPIO, 0x1),
> +	MFD_DEV_WITH_ID(GPIO, 0x2),
> +	MFD_DEV_WITH_ID(GPIO, 0x3),
> +	MFD_DEV_WITH_ID(GPIO, 0x4),
> +	MFD_DEV_WITH_ID(GPIO, 0x5),
> +	MFD_DEV_WITH_ID(GPIO, 0x6),
> +	MFD_DEV_WITH_ID(GPIO, 0x7),
> +	MFD_DEV_WITH_ID(GPIO, 0x8),
> +	MFD_DEV_WITH_ID(GPIO, 0x9),
> +	MFD_DEV_WITH_ID(GPIO, 0xA),
> +	MFD_DEV_WITH_ID(GPIO, 0xB),
> +	MFD_DEV_WITH_ID(GPIO, 0xC),
> +	MFD_DEV_WITH_ID(GPIO, 0xD),
> +	MFD_DEV_WITH_ID(GPIO, 0xE),
> +	MFD_DEV_WITH_ID(GPIO, 0xF),
> +
> +	MFD_DEV_WITH_ID(I2C, 0x0),
> +	MFD_DEV_WITH_ID(I2C, 0x1),
> +	MFD_DEV_WITH_ID(I2C, 0x2),
> +	MFD_DEV_WITH_ID(I2C, 0x3),
> +	MFD_DEV_WITH_ID(I2C, 0x4),
> +	MFD_DEV_WITH_ID(I2C, 0x5),
> +
> +	MFD_DEV_WITH_ID(CAN, 0x0),
> +	MFD_DEV_WITH_ID(CAN, 0x1),
> +
> +	MFD_DEV_WITH_ID(WDT, 0x0),
> +	MFD_DEV_WITH_ID(WDT, 0x1),
> +
> +	MFD_DEV_SIMPLE(HWMON),
> +	MFD_DEV_SIMPLE(RTC),
> +};
> +
> +static int nct6694_response_err_handling(struct nct6694 *nct6694,
> +					 unsigned char err_status)
> +{
> +	struct device *dev = &nct6694->udev->dev;
> +
> +	switch (err_status) {
> +	case NCT6694_NO_ERROR:
> +		return err_status;
> +	case NCT6694_NOT_SUPPORT_ERROR:
> +		dev_dbg(dev, "%s: Command is not support!\n", __func__);
> +		break;
> +	case NCT6694_NO_RESPONSE_ERROR:
> +		dev_dbg(dev, "%s: Command is no response!\n", __func__);
> +		break;
> +	case NCT6694_TIMEOUT_ERROR:
> +		dev_dbg(dev, "%s: Command is timeout!\n", __func__);
> +		break;
> +	case NCT6694_PENDING:
> +		dev_dbg(dev, "%s: Command is pending!\n", __func__);
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return -EIO;
> +}
> +
> +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;

RCT violation

> +	struct usb_device *udev = nct6694->udev;
> +	int tx_len, rx_len, ret;
> +
> +	guard(mutex)(&nct6694->access_lock);
> +
> +	/* 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;

Same as above

> +	struct usb_device *udev = nct6694->udev;
> +	int tx_len, rx_len, ret;
> +
> +	guard(mutex)(&nct6694->access_lock);
> +
> +	/* 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_SET;
> +	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;
> +
> +	ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, NCT6694_BULK_OUT_EP),
> +			   buf, length, &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_write_msg);
> +
> +static void usb_int_callback(struct urb *urb)
> +{
> +	struct nct6694 *nct6694 = urb->context;
> +	struct device *dev = &nct6694->udev->dev;
> +	unsigned int *int_status = urb->transfer_buffer;

Again RCT violation

> +	int ret;
> +
> +	switch (urb->status) {
> +	case 0:
> +		break;
> +	case -ECONNRESET:
> +	case -ENOENT:
> +	case -ESHUTDOWN:
> +		return;
> +	default:
> +		goto resubmit;
> +	}
> +
> +	while (*int_status) {
> +		int irq = __ffs(*int_status);
> +
> +		if (*int_status & (1 << irq))
> +			generic_handle_irq_safe(irq_find_mapping(nct6694->domain, irq));
> +
> +		*int_status &= ~(1 << irq);
> +	}
> +
> +resubmit:
> +	ret = usb_submit_urb(urb, GFP_ATOMIC);
> +	if (ret)
> +		dev_dbg(dev, "%s: Failed to resubmit urb, status %d",
> +			__func__, ret);
> +}
> +
> +static void nct6694_irq_lock(struct irq_data *data)
> +{
> +	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
> +
> +	mutex_lock(&nct6694->irq_lock);
> +}
> +
> +static void nct6694_irq_sync_unlock(struct irq_data *data)
> +{
> +	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
> +
> +	mutex_unlock(&nct6694->irq_lock);
> +}
> +
> +static void nct6694_irq_enable(struct irq_data *data)
> +{
> +	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
> +	unsigned int irq = data->hwirq;
> +
> +	nct6694->irq_enable |= (1 << irq);

I wonder if this is necessary to create local variable irq
if this is used only once. Maybe instead:

nct6694->irq_enable |= (1 << data->hwirq);

Not big thing though

> +}
> +
> +static void nct6694_irq_disable(struct irq_data *data)
> +{
> +	struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
> +	unsigned int irq = data->hwirq;
> +
> +	nct6694->irq_enable &= ~(1 << irq);
> +}
> +
> +static struct irq_chip nct6694_irq_chip = {
> +	.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_irq_domain_map(struct irq_domain *d, unsigned int irq,
> +				  irq_hw_number_t hw)
> +{
> +	struct nct6694 *nct6694 = d->host_data;
> +
> +	irq_set_chip_data(irq, nct6694);
> +	irq_set_chip_and_handler(irq, &nct6694_irq_chip, handle_simple_irq);
> +
> +	return 0;
> +}
> +
> +static void nct6694_irq_domain_unmap(struct irq_domain *d, unsigned int irq)
> +{
> +	irq_set_chip_and_handler(irq, NULL, NULL);
> +	irq_set_chip_data(irq, NULL);
> +}
> +
> +static const struct irq_domain_ops nct6694_irq_domain_ops = {
> +	.map	= nct6694_irq_domain_map,
> +	.unmap	= nct6694_irq_domain_unmap,
> +};
> +
> +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;

Please follow RCT rule

> +
> +	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);
> +	if (!nct6694->int_buffer)
> +		return -ENOMEM;
> +
> +	nct6694->int_in_urb = usb_alloc_urb(0, GFP_KERNEL);
> +	if (!nct6694->int_in_urb)
> +		return -ENOMEM;> +
> +	nct6694->domain = irq_domain_add_simple(NULL, NCT6694_NR_IRQS, 0,
> +						&nct6694_irq_domain_ops,
> +						nct6694);
> +	if (!nct6694->domain)
> +		return -ENODEV;
> +
> +	nct6694->udev = udev;
> +	nct6694->timeout = NCT6694_URB_TIMEOUT;	/* Wait until urb complete */
> +	nct6694->cmd_header = cmd_header;
> +	nct6694->response_header = response_header;
> +
> +	mutex_init(&nct6694->access_lock);
> +	mutex_init(&nct6694->irq_lock);
> +
> +	usb_fill_int_urb(nct6694->int_in_urb, udev, pipe,
> +			 nct6694->int_buffer, maxp, usb_int_callback,
> +			 nct6694, int_endpoint->bInterval);
> +	ret = usb_submit_urb(nct6694->int_in_urb, GFP_KERNEL);
> +	if (ret)
> +		goto err_urb;
> +
> +	dev_set_drvdata(dev, nct6694);
> +	usb_set_intfdata(iface, nct6694);
> +
> +	ret = mfd_add_hotplug_devices(dev, nct6694_dev, ARRAY_SIZE(nct6694_dev));
> +	if (ret)
> +		goto err_mfd;
> +
> +	dev_info(dev, "Probed device: (%04X:%04X)\n", id->idVendor, id->idProduct);
> +	return 0;
> +
> +err_mfd:
> +	usb_kill_urb(nct6694->int_in_urb);
> +err_urb:
> +	usb_free_urb(nct6694->int_in_urb);
> +	return dev_err_probe(dev, ret, "Probe failed\n");
> +}
> +
> +static void nct6694_usb_disconnect(struct usb_interface *iface)
> +{
> +	struct usb_device *udev = interface_to_usbdev(iface);
> +	struct nct6694 *nct6694 = usb_get_intfdata(iface);
> +
> +	mfd_remove_devices(&udev->dev);
> +	usb_kill_urb(nct6694->int_in_urb);
> +	usb_free_urb(nct6694->int_in_urb);
> +}
> +
> +static const struct usb_device_id nct6694_ids[] = {
> +	{ USB_DEVICE_AND_INTERFACE_INFO(NCT6694_VENDOR_ID,
> +					NCT6694_PRODUCT_ID,
> +					0xFF, 0x00, 0x00)},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(usb, nct6694_ids);
> +
> +static struct usb_driver nct6694_usb_driver = {
> +	.name	= "nct6694",
> +	.id_table = nct6694_ids,
> +	.probe = nct6694_usb_probe,
> +	.disconnect = nct6694_usb_disconnect,
> +};
> +
> +module_usb_driver(nct6694_usb_driver);
> +
> +MODULE_DESCRIPTION("USB-MFD driver for NCT6694");
> +MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/mfd/nct6694.h b/include/linux/mfd/nct6694.h
> new file mode 100644
> index 000000000000..9733d47f5a01
> --- /dev/null
> +++ b/include/linux/mfd/nct6694.h
> @@ -0,0 +1,139 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Nuvoton NCT6694 USB transaction and data structure.
> + *
> + * Copyright (C) 2024 Nuvoton Technology Corp.
> + */
> +
> +#ifndef __MFD_NCT6694_H
> +#define __MFD_NCT6694_H
> +
> +#define NCT6694_DEV_GPIO	"nct6694-gpio"
> +#define NCT6694_DEV_I2C		"nct6694-i2c"
> +#define NCT6694_DEV_CAN		"nct6694-can"
> +#define NCT6694_DEV_WDT		"nct6694-wdt"
> +#define NCT6694_DEV_HWMON	"nct6694-hwmon"
> +#define NCT6694_DEV_RTC		"nct6694-rtc"
> +
> +#define NCT6694_VENDOR_ID	0x0416
> +#define NCT6694_PRODUCT_ID	0x200B
> +#define NCT6694_INT_IN_EP	0x81
> +#define NCT6694_BULK_IN_EP	0x02
> +#define NCT6694_BULK_OUT_EP	0x03
> +#define NCT6694_MAX_PACKET_SZ	0x200
> +
> +#define NCT6694_CMD_PACKET_SZ	0x8
> +#define NCT6694_HCTRL_SET	0x40
> +#define NCT6694_HCTRL_GET	0x80
> +
> +#define NCT6694_URB_TIMEOUT	1000
> +
> +enum nct6694_irq_id {
> +	NCT6694_IRQ_GPIO0 = 0,
> +	NCT6694_IRQ_GPIO1,
> +	NCT6694_IRQ_GPIO2,
> +	NCT6694_IRQ_GPIO3,
> +	NCT6694_IRQ_GPIO4,
> +	NCT6694_IRQ_GPIO5,
> +	NCT6694_IRQ_GPIO6,
> +	NCT6694_IRQ_GPIO7,
> +	NCT6694_IRQ_GPIO8,
> +	NCT6694_IRQ_GPIO9,
> +	NCT6694_IRQ_GPIOA,
> +	NCT6694_IRQ_GPIOB,
> +	NCT6694_IRQ_GPIOC,
> +	NCT6694_IRQ_GPIOD,
> +	NCT6694_IRQ_GPIOE,
> +	NCT6694_IRQ_GPIOF,
> +	NCT6694_IRQ_CAN1,
> +	NCT6694_IRQ_CAN2,
> +	NCT6694_IRQ_RTC,
> +	NCT6694_NR_IRQS,
> +};
> +
> +enum nct6694_response_err_status {
> +	NCT6694_NO_ERROR = 0,
> +	NCT6694_FORMAT_ERROR,
> +	NCT6694_RESERVED1,
> +	NCT6694_RESERVED2,
> +	NCT6694_NOT_SUPPORT_ERROR,
> +	NCT6694_NO_RESPONSE_ERROR,
> +	NCT6694_TIMEOUT_ERROR,
> +	NCT6694_PENDING,
> +};
> +
> +struct nct6694 {
> +	struct usb_device *udev;
> +	struct urb *int_in_urb;
> +	struct irq_domain *domain;
> +	struct nct6694_cmd_header *cmd_header;
> +	struct nct6694_response_header *response_header;
> +	struct mutex access_lock;
> +	struct mutex irq_lock;
> +	unsigned char *int_buffer;
> +	unsigned int irq_enable;
> +	/* time in msec to wait for the urb to the complete */
> +	long timeout;
> +};
> +
> +struct nct6694_cmd_header {
> +	unsigned char rsv1;
> +	unsigned char mod;
> +	unsigned char cmd;
> +	unsigned char sel;
> +	unsigned char hctrl;
> +	unsigned char rsv2;
> +	unsigned short len;
> +} __packed;
> +
> +struct nct6694_response_header {
> +	unsigned char sequence_id;
> +	unsigned char sts;
> +	unsigned int rsv;
> +	unsigned short len;
> +} __packed;
> +
> +/*
> + * nct6694_read_msg - Receive data from NCT6694 USB device
> + *
> + * @nct6694 - Nuvoton NCT6694 structure
> + * @mod - Module byte
> + * @offset - Offset byte or (Select byte | Command byte)
> + * @length - Length byte
> + * @buf - Read data from rx buffer
> + *
> + * USB Transaction format:
> + *
> + *	OUT	|RSV|MOD|CMD|SEL|HCTL|RSV|LEN_L|LEN_H|
> + *	OUT	|SEQ|STS|RSV|RSV|RSV|RSV||LEN_L|LEN_H|
> + *	IN	|-------D------A------D------A-------|
> + *	IN			......
> + *	IN	|-------D------A------D------A-------|
> + */
> +int nct6694_read_msg(struct nct6694 *nct6694, u8 mod, u16 offset,
> +		     u16 length, void *buf);
> +
> +/*
> + * nct6694_read_msg - Transmit data to NCT6694 USB device
> + *
> + * @nct6694 - Nuvoton NCT6694 structure
> + * @mod - Module byte
> + * @offset - Offset byte or (Select byte | Command byte)
> + * @length - Length byte
> + * @buf - Write data to tx buffer
> + *
> + * USB Transaction format:
> + *
> + *	OUT	|RSV|MOD|CMD|SEL|HCTL|RSV|LEN_L|LEN_H|
> + *	OUT	|-------D------A------D------A-------|
> + *	OUT			......
> + *	OUT	|-------D------A------D------A-------|
> + *	IN	|SEQ|STS|RSV|RSV|RSV|RSV||LEN_L|LEN_H|
> + *	IN	|-------D------A------D------A-------|
> + *	IN			......
> + *	IN	|-------D------A------D------A-------|
> + */
> +int nct6694_write_msg(struct nct6694 *nct6694, u8 mod, u16 offset,
> +		      u16 length, void *buf);
> +
> +#endif

On Tue, 10 Dec 2024 11:57:41 +0100 Mateusz Polchlopek wrote:
> > +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;  
> 
> RCT violation

This code is not under net not drivers/net
As a general rule please focus on functional review, formatting and
process issues are harder to judge unless you read all of the mailing
list traffic.