[PATCH v1 1/9] mfd: Add core driver for Nuvoton NCT6694

Ming Yu
2024-10-24T08:59:50Z

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 register
a handler function 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 | 394 ++++++++++++++++++++++++++++++++++++
include/linux/mfd/nct6694.h | 168 +++++++++++++++
5 files changed, 581 insertions(+)
create mode 100644 drivers/mfd/nct6694.c
create mode 100644 include/linux/mfd/nct6694.h

diff --git a/MAINTAINERS b/MAINTAINERS
index e9659a5a7fb3..30157ca95cf3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16434,6 +16434,13 @@ 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 f9325bcce1b9..da2600958697 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -546,6 +546,16 @@ 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 2a9f91e81af8..2cf816d67d03 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -116,6 +116,8 @@ 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..9838c7be0b98
--- /dev/null
+++ b/drivers/mfd/nct6694.c
@@ -0,0 +1,394 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 MFD driver based on USB interface.
+ *
+ * Copyright (C) 2024 Nuvoton Technology Corp.
+ */
+
+#include <linux/io.h>
+#include <linux/usb.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/nct6694.h>
+
+#define DRVNAME "nct6694-usb_mfd"
+
+#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(IIO),
+ MFD_DEV_SIMPLE(HWMON),
+ MFD_DEV_SIMPLE(PWM),
+ MFD_DEV_SIMPLE(RTC),
+};
+
+int nct6694_register_handler(struct nct6694 *nct6694, int irq_bit,
+ void (*handler)(void *), void *private_data)
+{
+ struct nct6694_handler_entry *entry;
+ unsigned long flags;
+
+ entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry)
+ return -ENOMEM;
+
+ entry->irq_bit = irq_bit;
+ entry->handler = handler;
+ entry->private_data = private_data;
+
+ spin_lock_irqsave(&nct6694->lock, flags);
+ list_add_tail(&entry->list, &nct6694->handler_list);
+ spin_unlock_irqrestore(&nct6694->lock, flags);
+
+ return 0;
+}
+EXPORT_SYMBOL(nct6694_register_handler);
+
+int nct6694_read_msg(struct nct6694 *nct6694, u8 mod, u16 offset, u16 length,
+ u8 rd_idx, u8 rd_len, unsigned char *buf)
+{
+ struct usb_device *udev = nct6694->udev;
+ unsigned char err_status;
+ int len, packet_len, tx_len, rx_len;
+ int i, ret;
+
+ mutex_lock(&nct6694->access_lock);
+
+ /* Send command packet to USB device */
+ nct6694->cmd_buffer[REQUEST_MOD_IDX] = mod;
+ nct6694->cmd_buffer[REQUEST_CMD_IDX] = offset & 0xFF;
+ nct6694->cmd_buffer[REQUEST_SEL_IDX] = (offset >> 8) & 0xFF;
+ nct6694->cmd_buffer[REQUEST_HCTRL_IDX] = HCTRL_GET;
+ nct6694->cmd_buffer[REQUEST_LEN_L_IDX] = length & 0xFF;
+ nct6694->cmd_buffer[REQUEST_LEN_H_IDX] = (length >> 8) & 0xFF;
+
+ ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, BULK_OUT_ENDPOINT),
+ nct6694->cmd_buffer, CMD_PACKET_SZ, &tx_len,
+ nct6694->timeout);
+ if (ret)
+ goto err;
+
+ /* Receive response packet from USB device */
+ ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, BULK_IN_ENDPOINT),
+ nct6694->rx_buffer, CMD_PACKET_SZ, &rx_len,
+ nct6694->timeout);
+ if (ret)
+ goto err;
+
+ err_status = nct6694->rx_buffer[RESPONSE_STS_IDX];
+
+ /*
+ * Segmented reception of messages that exceed the size of USB bulk
+ * pipe packets.
+ */
+ for (i = 0, len = length; len > 0; i++, len -= packet_len) {
+ if (len > nct6694->maxp)
+ packet_len = nct6694->maxp;
+ else
+ packet_len = len;
+
+ ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, BULK_IN_ENDPOINT),
+ nct6694->rx_buffer + nct6694->maxp * i,
+ packet_len, &rx_len, nct6694->timeout);
+ if (ret)
+ goto err;
+ }
+
+ for (i = 0; i < rd_len; i++)
+ buf[i] = nct6694->rx_buffer[i + rd_idx];
+
+ if (err_status) {
+ pr_debug("%s: MSG CH status = %2Xh\n", __func__, err_status);
+ ret = -EIO;
+ }
+
+err:
+ mutex_unlock(&nct6694->access_lock);
+ return ret;
+}
+EXPORT_SYMBOL(nct6694_read_msg);
+
+int nct6694_write_msg(struct nct6694 *nct6694, u8 mod, u16 offset,
+ u16 length, unsigned char *buf)
+{
+ struct usb_device *udev = nct6694->udev;
+ unsigned char err_status;
+ int len, packet_len, tx_len, rx_len;
+ int i, ret;
+
+ mutex_lock(&nct6694->access_lock);
+
+ /* Send command packet to USB device */
+ nct6694->cmd_buffer[REQUEST_MOD_IDX] = mod;
+ nct6694->cmd_buffer[REQUEST_CMD_IDX] = offset & 0xFF;
+ nct6694->cmd_buffer[REQUEST_SEL_IDX] = (offset >> 8) & 0xFF;
+ nct6694->cmd_buffer[REQUEST_HCTRL_IDX] = HCTRL_SET;
+ nct6694->cmd_buffer[REQUEST_LEN_L_IDX] = length & 0xFF;
+ nct6694->cmd_buffer[REQUEST_LEN_H_IDX] = (length >> 8) & 0xFF;
+
+ ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, BULK_OUT_ENDPOINT),
+ nct6694->cmd_buffer, CMD_PACKET_SZ, &tx_len,
+ nct6694->timeout);
+ if (ret)
+ goto err;
+
+ /*
+ * Segmented transmission of messages that exceed the size of USB bulk
+ * pipe packets.
+ */
+ for (i = 0, len = length; len > 0; i++, len -= packet_len) {
+ if (len > nct6694->maxp)
+ packet_len = nct6694->maxp;
+ else
+ packet_len = len;
+
+ memcpy(nct6694->tx_buffer + nct6694->maxp * i,
+ buf + nct6694->maxp * i, packet_len);
+
+ ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, BULK_OUT_ENDPOINT),
+ nct6694->tx_buffer + nct6694->maxp * i,
+ packet_len, &tx_len, nct6694->timeout);
+ if (ret)
+ goto err;
+ }
+
+ /* Receive response packet from USB device */
+ ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, BULK_IN_ENDPOINT),
+ nct6694->rx_buffer, CMD_PACKET_SZ, &rx_len,
+ nct6694->timeout);
+ if (ret)
+ goto err;
+
+ err_status = nct6694->rx_buffer[RESPONSE_STS_IDX];
+
+ /*
+ * Segmented reception of messages that exceed the size of USB bulk
+ * pipe packets.
+ */
+ for (i = 0, len = length; len > 0; i++, len -= packet_len) {
+ if (len > nct6694->maxp)
+ packet_len = nct6694->maxp;
+ else
+ packet_len = len;
+
+ ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, BULK_IN_ENDPOINT),
+ nct6694->rx_buffer + nct6694->maxp * i,
+ packet_len, &rx_len, nct6694->timeout);
+ if (ret)
+ goto err;
+ }
+
+ memcpy(buf, nct6694->rx_buffer, length);
+
+ if (err_status) {
+ pr_debug("%s: MSG CH status = %2Xh\n", __func__, err_status);
+ ret = -EIO;
+ }
+
+err:
+ mutex_unlock(&nct6694->access_lock);
+ return ret;
+}
+EXPORT_SYMBOL(nct6694_write_msg);
+
+static void usb_int_callback(struct urb *urb)
+{
+ unsigned char *int_status = urb->transfer_buffer;
+ struct nct6694 *nct6694 = urb->context;
+ struct nct6694_handler_entry *entry;
+ unsigned long flags;
+ int ret;
+
+ switch (urb->status) {
+ case 0:
+ break;
+ case -ECONNRESET:
+ case -ENOENT:
+ case -ESHUTDOWN:
+ return;
+ default:
+ goto resubmit;
+ }
+
+ spin_lock_irqsave(&nct6694->lock, flags);
+
+ list_for_each_entry(entry, &nct6694->handler_list, list) {
+ if (int_status[INT_IN_IRQ_IDX] & entry->irq_bit)
+ entry->handler(entry->private_data);
+ }
+
+ spin_unlock_irqrestore(&nct6694->lock, flags);
+
+resubmit:
+ ret = usb_submit_urb(urb, GFP_ATOMIC);
+ if (ret)
+ pr_debug("%s: Failed to resubmit urb, status %d",
+ __func__, ret);
+}
+
+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;
+ int pipe, maxp, bulk_pipe;
+ int ret = EINVAL;
+
+ interface = iface->cur_altsetting;
+ /* Binding interface class : 0xFF */
+ if (interface->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC ||
+ interface->desc.bInterfaceSubClass != 0x00 ||
+ interface->desc.bInterfaceProtocol != 0x00)
+ return -ENODEV;
+
+ int_endpoint = &interface->endpoint[0].desc;
+ if (!usb_endpoint_is_int_in(int_endpoint))
+ return -ENODEV;
+
+ nct6694 = devm_kzalloc(&udev->dev, sizeof(*nct6694), GFP_KERNEL);
+ if (!nct6694)
+ return -ENOMEM;
+
+ pipe = usb_rcvintpipe(udev, INT_IN_ENDPOINT);
+ maxp = usb_maxpacket(udev, pipe);
+
+ nct6694->cmd_buffer = devm_kcalloc(dev, CMD_PACKET_SZ,
+ sizeof(unsigned char), GFP_KERNEL);
+ if (!nct6694->cmd_buffer)
+ return -ENOMEM;
+ nct6694->rx_buffer = devm_kcalloc(dev, MAX_PACKET_SZ,
+ sizeof(unsigned char), GFP_KERNEL);
+ if (!nct6694->rx_buffer)
+ return -ENOMEM;
+ nct6694->tx_buffer = devm_kcalloc(dev, MAX_PACKET_SZ,
+ sizeof(unsigned char), GFP_KERNEL);
+ if (!nct6694->tx_buffer)
+ return -ENOMEM;
+ nct6694->int_buffer = devm_kcalloc(dev, 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) {
+ dev_err(&udev->dev, "Failed to allocate INT-in urb!\n");
+ return -ENOMEM;
+ }
+
+ /* Bulk pipe maximum packet for each transaction */
+ bulk_pipe = usb_sndbulkpipe(udev, BULK_OUT_ENDPOINT);
+ nct6694->maxp = usb_maxpacket(udev, bulk_pipe);
+
+ mutex_init(&nct6694->access_lock);
+ nct6694->udev = udev;
+ nct6694->timeout = URB_TIMEOUT; /* Wait until urb complete */
+
+ INIT_LIST_HEAD(&nct6694->handler_list);
+ spin_lock_init(&nct6694->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(&udev->dev, nct6694);
+ usb_set_intfdata(iface, nct6694);
+
+ ret = mfd_add_hotplug_devices(&udev->dev, nct6694_dev,
+ ARRAY_SIZE(nct6694_dev));
+ if (ret) {
+ dev_err(&udev->dev, "Failed to add mfd's child device\n");
+ goto err_mfd;
+ }
+
+ nct6694->async_workqueue = alloc_ordered_workqueue("asyn_workqueue", 0);
+
+ dev_info(&udev->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 ret;
+}
+
+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);
+ flush_workqueue(nct6694->async_workqueue);
+ destroy_workqueue(nct6694->async_workqueue);
+ usb_set_intfdata(iface, NULL);
+ usb_kill_urb(nct6694->int_in_urb);
+ usb_free_urb(nct6694->int_in_urb);
+}
+
+static const struct usb_device_id nct6694_ids[] = {
+ { USB_DEVICE(NCT6694_VENDOR_ID, NCT6694_PRODUCT_ID)},
+ {},
+};
+MODULE_DEVICE_TABLE(usb, nct6694_ids);
+
+static struct usb_driver nct6694_usb_driver = {
+ .name = DRVNAME,
+ .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..0797564363be
--- /dev/null
+++ b/include/linux/mfd/nct6694.h
@@ -0,0 +1,168 @@
+/* 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_IIO "nct6694-iio"
+#define NCT6694_DEV_HWMON "nct6694-hwmon"
+#define NCT6694_DEV_PWM "nct6694-pwm"
+#define NCT6694_DEV_RTC "nct6694-rtc"
+
+#define NCT6694_VENDOR_ID 0x0416
+#define NCT6694_PRODUCT_ID 0x200B
+#define INT_IN_ENDPOINT 0x81
+#define BULK_IN_ENDPOINT 0x82
+#define BULK_OUT_ENDPOINT 0x03
+#define MAX_PACKET_SZ 0x100
+
+#define CMD_PACKET_SZ 0x8
+#define HCTRL_SET 0x40
+#define HCTRL_GET 0x80
+
+#define REQUEST_MOD_IDX 0x01
+#define REQUEST_CMD_IDX 0x02
+#define REQUEST_SEL_IDX 0x03
+#define REQUEST_HCTRL_IDX 0x04
+#define REQUEST_LEN_L_IDX 0x06
+#define REQUEST_LEN_H_IDX 0x07
+
+#define RESPONSE_STS_IDX 0x01
+
+#define INT_IN_IRQ_IDX 0x00
+#define GPIO_IRQ_STATUS BIT(0)
+#define CAN_IRQ_STATUS BIT(2)
+#define RTC_IRQ_STATUS BIT(3)
+
+#define URB_TIMEOUT 1000
+
+/*
+ * struct nct6694 - Nuvoton NCT6694 structure
+ *
+ * @udev: Pointer to the USB device
+ * @int_in_urb: Interrupt pipe urb
+ * @access_lock: USB transaction lock
+ * @handler_list: List of registered handlers
+ * @async_workqueue: Workqueue of processing asynchronous work
+ * @tx_buffer: USB write message buffer
+ * @rx_buffer: USB read message buffer
+ * @cmd_buffer: USB send command message buffer
+ * @int_buffer: USB receive interrupt message buffer
+ * @lock: Handlers lock
+ * @timeout: URB timeout
+ * @maxp: Maximum packet of bulk pipe
+ */
+struct nct6694 {
+ struct usb_device *udev;
+ struct urb *int_in_urb;
+ struct list_head handler_list;
+ struct workqueue_struct *async_workqueue;
+
+ /* Make sure that every USB transaction is not interrupted */
+ struct mutex access_lock;
+
+ unsigned char *tx_buffer;
+ unsigned char *rx_buffer;
+ unsigned char *cmd_buffer;
+ unsigned char *int_buffer;
+
+ /* Prevent races within handlers */
+ spinlock_t lock;
+
+ /* time in msec to wait for the urb to the complete */
+ long timeout;
+
+ /* Bulk pipe maximum packet for each transaction */
+ int maxp;
+};
+
+/*
+ * struct nct6694_handler_entry - Stores the interrupt handling information
+ * for each registered peripheral
+ *
+ * @irq_bit: The bit in irq_status[INT_IN_IRQ_IDX] representing interrupt
+ * @handler: Function pointer to the interrupt handler of the peripheral
+ * @private_data: Private data specific to the peripheral driver
+ * @list: Node used to link to the handler_list
+ */
+struct nct6694_handler_entry {
+ int irq_bit;
+ void (*handler)(void *private_data);
+ void *private_data;
+ struct list_head list;
+};
+
+/*
+ * nct6694_register_handler - Register a handler with private data for
+ * interrupt pipe irq event
+ *
+ * @nct6694 - Nuvoton NCT6694 structure
+ * @irq_bit - The irq for which to register a handler
+ * @handler - The handler function
+ * @private_data - Private data for which to register a handler
+ *
+ * This function is called when peripherals need to register a handler
+ * for receiving interrupt pipe.
+ *
+ * Don't use the wait_for_completion function in handler function, as
+ * it is in interrupt context.
+ */
+int nct6694_register_handler(struct nct6694 *nct6694, int irq_bit,
+ void (*handler)(void *),
+ void *private_data);
+
+/*
+ * 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
+ * @rd_idx - Read data from rx buffer at index
+ * @rd_len - Read length from rx buffer
+ * @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, u8 rd_idx, u8 rd_len,
+ unsigned char *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, unsigned char *buf);
+
+#endif
--
2.34.1