Re: [PATCH v12 1/7] mfd: Add core driver for Nuvoton NCT6694

[Oliver Neukum <oneukum@suse.com>]

On 04.06.25 06:14, a0282524688@gmail.com wrote:
> From: Ming Yu <tmyu0@nuvoton.com>
> 
> The Nuvoton NCT6694 provides an USB interface to the host to
> access its features.
> 
> Sub-devices 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>
> ---
> Changes since version 11:
> - Modify the irq_domain_add_simple() to irq_domain_create_simple()
> - Fix mfd_cell back to v9, and use Use platform_device's id to replace IDA
>    in sub-drivers
> 
> Changes since version 10:
> - Add change log for the patch
> - Fix mfd_cell to MFD_CELL_NAME()
> - Remove unnecessary blank line
> 
> Changes since version 9:
> - Add KernelDoc to exported functions
> 
> Changes since version 8:
> - Modify the signed-off-by with my work address
> - Rename all MFD cell names to "nct6694-xxx"
> - Fix some comments in nct6694.c and in nct6694.h
> 
> Changes since version 7:
> - Add error handling for devm_mutex_init()
> 
> Changes since version 6:
> 
> Changes since version 5:
> - Fix mfd_cell to MFD_CELL_NAME() and MFD_CELL_BASIC()
> - Drop unnecessary macros
> 
> Changes since version 4:
> - Modify arguments in read/write function to a pointer to cmd_header
> 
> Changes since version 3:
> - Modify array buffer to structure
> - Fix defines and comments
> - Add header <linux/bits.h> and use BIT macro
> - Modify mutex_init() to devm_mutex_init()
> 
> Changes since version 2:
> 
> Changes since version 1:
> - Implement IRQ domain to handle IRQ demux
> - Modify USB_DEVICE to USB_DEVICE_AND_INTERFACE_INFO API
> - Add command structure
> - Fix USB functions
> - Sort each driver's header files alphabetically
> 
>   MAINTAINERS                 |   6 +
>   drivers/mfd/Kconfig         |  15 ++
>   drivers/mfd/Makefile        |   2 +
>   drivers/mfd/nct6694.c       | 386 ++++++++++++++++++++++++++++++++++++
>   include/linux/mfd/nct6694.h |  98 +++++++++
>   5 files changed, 507 insertions(+)
>   create mode 100644 drivers/mfd/nct6694.c
>   create mode 100644 include/linux/mfd/nct6694.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 98201e1f4ab5..29d2d05bac22 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -17679,6 +17679,12 @@ F:	drivers/nubus/
>   F:	include/linux/nubus.h
>   F:	include/uapi/linux/nubus.h
>   
> +NUVOTON NCT6694 MFD DRIVER
> +M:	Ming Yu <tmyu0@nuvoton.com>
> +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 96992af22565..489c1950f1ac 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1078,6 +1078,21 @@ config MFD_MENF21BMC
>   	  This driver can also be built as a module. If so the module
>   	  will be called menf21bmc.
>   
> +config MFD_NCT6694
> +	tristate "Nuvoton NCT6694 support"
> +	select MFD_CORE
> +	depends on USB
> +	help
> +	  This enables support for the Nuvoton USB device NCT6694, which shares
> +	  peripherals.
> +	  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 provides core APIs to access the NCT6694 hardware
> +	  monitoring and control features.
> +	  Additional drivers must be enabled to utilize the specific
> +	  functionalities of the device.
> +
>   config MFD_OCELOT
>   	tristate "Microsemi Ocelot External Control Support"
>   	depends on SPI_MASTER
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 5e5cc279af60..a96204d938fc 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -120,6 +120,8 @@ obj-$(CONFIG_MFD_MC13XXX)	+= mc13xxx-core.o
>   obj-$(CONFIG_MFD_MC13XXX_SPI)	+= mc13xxx-spi.o
>   obj-$(CONFIG_MFD_MC13XXX_I2C)	+= mc13xxx-i2c.o
>   
> +obj-$(CONFIG_MFD_NCT6694)	+= nct6694.o
> +
>   obj-$(CONFIG_MFD_CORE)		+= mfd-core.o
>   
>   ocelot-soc-objs			:= ocelot-core.o ocelot-spi.o
> diff --git a/drivers/mfd/nct6694.c b/drivers/mfd/nct6694.c
> new file mode 100644
> index 000000000000..82d378ee47ed
> --- /dev/null
> +++ b/drivers/mfd/nct6694.c
> @@ -0,0 +1,386 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2025 Nuvoton Technology Corp.
> + *
> + * Nuvoton NCT6694 core driver using USB interface to provide
> + * access to the NCT6694 hardware monitoring and control features.
> + *
> + * The NCT6694 is an integrated controller that provides GPIO, I2C,
> + * CAN, WDT, HWMON and RTC management.
> + */
> +
> +#include <linux/bits.h>
> +#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>
> +
> +static const struct mfd_cell nct6694_devs[] = {
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 0),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 1),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 2),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 3),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 4),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 5),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 6),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 7),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 8),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 9),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 10),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 11),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 12),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 13),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 14),
> +	MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 15),
> +
> +	MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 0),
> +	MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 1),
> +	MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 2),
> +	MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 3),
> +	MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 4),
> +	MFD_CELL_BASIC("nct6694-i2c", NULL, NULL, 0, 5),
> +
> +	MFD_CELL_BASIC("nct6694-canfd", NULL, NULL, 0, 0),
> +	MFD_CELL_BASIC("nct6694-canfd", NULL, NULL, 0, 1),
> +
> +	MFD_CELL_BASIC("nct6694-wdt", NULL, NULL, 0, 0),
> +	MFD_CELL_BASIC("nct6694-wdt", NULL, NULL, 0, 1),
> +
> +	MFD_CELL_NAME("nct6694-hwmon"),
> +
> +	MFD_CELL_NAME("nct6694-rtc"),
> +};
> +
> +static int nct6694_response_err_handling(struct nct6694 *nct6694, unsigned char err_status)
> +{
> +	switch (err_status) {
> +	case NCT6694_NO_ERROR:
> +		return 0;
> +	case NCT6694_NOT_SUPPORT_ERROR:
> +		dev_err(nct6694->dev, "Command is not supported!\n");
> +		break;
> +	case NCT6694_NO_RESPONSE_ERROR:
> +		dev_warn(nct6694->dev, "Command received no response!\n");
> +		break;
> +	case NCT6694_TIMEOUT_ERROR:
> +		dev_warn(nct6694->dev, "Command timed out!\n");
> +		break;
> +	case NCT6694_PENDING:
> +		dev_err(nct6694->dev, "Command is pending!\n");
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return -EIO;
> +}
> +
> +/**
> + * nct6694_read_msg() - Read message from NCT6694 device
> + * @nct6694: NCT6694 device pointer
> + * @cmd_hd: command header structure
> + * @buf: buffer to store the response data
> + *
> + * Sends a command to the NCT6694 device and reads the response.
> + * The command header is specified in @cmd_hd, and the response
> + * data is stored in @buf.
> + *
> + * Return: Negative value on error or 0 on success.
> + */
> +int nct6694_read_msg(struct nct6694 *nct6694, const struct nct6694_cmd_header *cmd_hd, void *buf)
> +{
> +	union nct6694_usb_msg *msg = nct6694->usb_msg;
> +	struct usb_device *udev = nct6694->udev;
> +	int tx_len, rx_len, ret;
> +
> +	guard(mutex)(&nct6694->access_lock);
> +
> +	memcpy(&msg->cmd_header, cmd_hd, sizeof(*cmd_hd));
> +	msg->cmd_header.hctrl = NCT6694_HCTRL_GET;
> +
> +	/* Send command packet to USB device */
> +	ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, NCT6694_BULK_OUT_EP), &msg->cmd_header,
> +			   sizeof(*msg), &tx_len, NCT6694_URB_TIMEOUT);
> +	if (ret)
> +		return ret;
> +
> +	/* Receive response packet from USB device */
> +	ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, NCT6694_BULK_IN_EP), &msg->response_header,
> +			   sizeof(*msg), &rx_len, NCT6694_URB_TIMEOUT);
> +	if (ret)
> +		return ret;
> +
> +	/* Receive data packet from USB device */
> +	ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, NCT6694_BULK_IN_EP), buf,
> +			   le16_to_cpu(cmd_hd->len), &rx_len, NCT6694_URB_TIMEOUT);
> +	if (ret)
> +		return ret;
> +
> +	if (rx_len != le16_to_cpu(cmd_hd->len)) {
> +		dev_err(nct6694->dev, "Expected received length %d, but got %d\n",
> +			le16_to_cpu(cmd_hd->len), rx_len);
> +		return -EIO;
> +	}
> +
> +	return nct6694_response_err_handling(nct6694, msg->response_header.sts);
> +}
> +EXPORT_SYMBOL_GPL(nct6694_read_msg);
> +
> +/**
> + * nct6694_write_msg() - Write message to NCT6694 device
> + * @nct6694: NCT6694 device pointer
> + * @cmd_hd: command header structure
> + * @buf: buffer containing the data to be sent
> + *
> + * Sends a command to the NCT6694 device and writes the data
> + * from @buf. The command header is specified in @cmd_hd.
> + *
> + * Return: Negative value on error or 0 on success.
> + */
> +int nct6694_write_msg(struct nct6694 *nct6694, const struct nct6694_cmd_header *cmd_hd, void *buf)
> +{
> +	union nct6694_usb_msg *msg = nct6694->usb_msg;
> +	struct usb_device *udev = nct6694->udev;
> +	int tx_len, rx_len, ret;
> +
> +	guard(mutex)(&nct6694->access_lock);
> +
> +	memcpy(&msg->cmd_header, cmd_hd, sizeof(*cmd_hd));
> +	msg->cmd_header.hctrl = NCT6694_HCTRL_SET;
> +
> +	/* Send command packet to USB device */
> +	ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, NCT6694_BULK_OUT_EP), &msg->cmd_header,
> +			   sizeof(*msg), &tx_len, NCT6694_URB_TIMEOUT);
> +	if (ret)
> +		return ret;
> +
> +	/* Send data packet to USB device */
> +	ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, NCT6694_BULK_OUT_EP), buf,
> +			   le16_to_cpu(cmd_hd->len), &tx_len, NCT6694_URB_TIMEOUT);
> +	if (ret)
> +		return ret;
> +
> +	/* Receive response packet from USB device */
> +	ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, NCT6694_BULK_IN_EP), &msg->response_header,
> +			   sizeof(*msg), &rx_len, NCT6694_URB_TIMEOUT);
> +	if (ret)
> +		return ret;
> +
> +	/* Receive data packet from USB device */
> +	ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, NCT6694_BULK_IN_EP), buf,
> +			   le16_to_cpu(cmd_hd->len), &rx_len, NCT6694_URB_TIMEOUT);
> +	if (ret)
> +		return ret;
> +
> +	if (rx_len != le16_to_cpu(cmd_hd->len)) {
> +		dev_err(nct6694->dev, "Expected transmitted length %d, but got %d\n",
> +			le16_to_cpu(cmd_hd->len), rx_len);
> +		return -EIO;
> +	}
> +
> +	return nct6694_response_err_handling(nct6694, msg->response_header.sts);
> +}
> +EXPORT_SYMBOL_GPL(nct6694_write_msg);
> +
> +static void usb_int_callback(struct urb *urb)
> +{
> +	struct nct6694 *nct6694 = urb->context;
> +	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);
> +
> +		generic_handle_irq_safe(irq_find_mapping(nct6694->domain, irq));
> +		*int_status &= ~BIT(irq);
> +	}

Does modifying the byte have any benefit?

> +resubmit:
> +	ret = usb_submit_urb(urb, GFP_ATOMIC);
> +	if (ret)
> +		dev_warn(nct6694->dev, "Failed to resubmit urb, status %pe",  ERR_PTR(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);
> +}

Why? Does this do anything but make it _harder_ to tell that you
cannot take the lock in interrupt?

	Regards
		Oliver