Re: [PATCH] staging: iio: adc: ad7816: remove obsolete driver

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 12 Oct 2026 15:41:42 +0100
Nuno Sá <nuno.sa@analog.com> wrote:

> On Tue, Oct 06, 2026 at 11:51:19AM +0000, Joshua Crofts wrote:
> > The AD7816 driver has been in staging for 16 years and hasn't seen any
> > significant improvements for it to mature out of staging.
> > 
> > Additionally, the AD7816/AD7817/AD7818 have been obsolete for ~11 years.

AD7817 is marked production.
https://www.analog.com/en/products/ad7817.html

That's the only reason I didn't drop this last time I checked the
staging parts.  
Still Nuno acked, so bye bye driver :)

Applied.


> > 
> > Remove the entire adc/ subdirectory and references to it as this is the
> > only driver in it.
> > 
> > Signed-off-by: Joshua Crofts <joshua.crofts1@gmail.com>
> > ---
> > If people want to use the AD7816, Analog Devices have their own fork of
> > the kernel where the driver is present [1].  
> 
> Just note that we do update the kernel so the removal will come to us
> :). Anyways, the part is indeed marked as obsolete so I'm not expecting
> any effort for updating the driver and remove it out of staging. So, fine
> by me. If any customers shouts, we can add the driver back in our fork
> (or add proper support for it) - but odds are low
> 
> So it is only fair to ack this:
> 
> Acked-by: Nuno Sá <nuno.sa@analog.com>
> 
> > 
> > Also, I don't see a point in keeping the driver for newcomers to
> > practice on, as all mechanical changes (checkpatch, cocci) have been
> > applied.
> > 
> > [1] https://github.com/analogdevicesinc/linux/blob/main/drivers/staging/iio/adc/ad7816.c
> > ---
> >  drivers/staging/iio/Kconfig      |   1 -
> >  drivers/staging/iio/Makefile     |   1 -
> >  drivers/staging/iio/adc/Kconfig  |  18 --
> >  drivers/staging/iio/adc/Makefile |   6 -
> >  drivers/staging/iio/adc/ad7816.c | 464 -------------------------------
> >  5 files changed, 490 deletions(-)
> >  delete mode 100644 drivers/staging/iio/adc/Kconfig
> >  delete mode 100644 drivers/staging/iio/adc/Makefile
> >  delete mode 100644 drivers/staging/iio/adc/ad7816.c
> > 
> > diff --git a/drivers/staging/iio/Kconfig b/drivers/staging/iio/Kconfig
> > index bf6addf2974f..58d6859e039a 100644
> > --- a/drivers/staging/iio/Kconfig
> > +++ b/drivers/staging/iio/Kconfig
> > @@ -5,7 +5,6 @@
> >  menu "IIO staging drivers"
> >  	depends on IIO
> >  
> > -source "drivers/staging/iio/adc/Kconfig"
> >  source "drivers/staging/iio/addac/Kconfig"
> >  source "drivers/staging/iio/frequency/Kconfig"
> >  source "drivers/staging/iio/impedance-analyzer/Kconfig"
> > diff --git a/drivers/staging/iio/Makefile b/drivers/staging/iio/Makefile
> > index 739e4cbf9a7a..7768c4a8d278 100644
> > --- a/drivers/staging/iio/Makefile
> > +++ b/drivers/staging/iio/Makefile
> > @@ -3,7 +3,6 @@
> >  # Makefile for the industrial I/O core.
> >  #
> >  
> > -obj-y += adc/
> >  obj-y += addac/
> >  obj-y += frequency/
> >  obj-y += impedance-analyzer/
> > diff --git a/drivers/staging/iio/adc/Kconfig b/drivers/staging/iio/adc/Kconfig
> > deleted file mode 100644
> > index 2f0d6cf048d2..000000000000
> > --- a/drivers/staging/iio/adc/Kconfig
> > +++ /dev/null
> > @@ -1,18 +0,0 @@
> > -# SPDX-License-Identifier: GPL-2.0
> > -#
> > -# ADC drivers
> > -#
> > -menu "Analog to digital converters"
> > -
> > -config AD7816
> > -	tristate "Analog Devices AD7816/7/8 temperature sensor and ADC driver"
> > -	depends on SPI
> > -	depends on GPIOLIB || COMPILE_TEST
> > -	help
> > -	  Say yes here to build support for Analog Devices AD7816/7/8
> > -	  temperature sensors and ADC.
> > -
> > -	  To compile this driver as a module, choose M here: the
> > -	  module will be called ad7816.
> > -
> > -endmenu
> > diff --git a/drivers/staging/iio/adc/Makefile b/drivers/staging/iio/adc/Makefile
> > deleted file mode 100644
> > index 1e2a94c4db84..000000000000
> > --- a/drivers/staging/iio/adc/Makefile
> > +++ /dev/null
> > @@ -1,6 +0,0 @@
> > -# SPDX-License-Identifier: GPL-2.0
> > -#
> > -# Makefile for industrial I/O ADC drivers
> > -#
> > -
> > -obj-$(CONFIG_AD7816) += ad7816.o
> > diff --git a/drivers/staging/iio/adc/ad7816.c b/drivers/staging/iio/adc/ad7816.c
> > deleted file mode 100644
> > index 2a15d7598abb..000000000000
> > --- a/drivers/staging/iio/adc/ad7816.c
> > +++ /dev/null
> > @@ -1,464 +0,0 @@
> > -// SPDX-License-Identifier: GPL-2.0+
> > -/*
> > - * AD7816 digital temperature sensor driver supporting AD7816/7/8
> > - *
> > - * Copyright 2010 Analog Devices Inc.
> > - */
> > -
> > -#include <linux/cleanup.h>
> > -#include <linux/device.h>
> > -#include <linux/gpio/consumer.h>
> > -#include <linux/interrupt.h>
> > -#include <linux/kernel.h>
> > -#include <linux/list.h>
> > -#include <linux/module.h>
> > -#include <linux/mutex.h>
> > -#include <linux/slab.h>
> > -#include <linux/spi/spi.h>
> > -#include <linux/sysfs.h>
> > -
> > -#include <linux/iio/events.h>
> > -#include <linux/iio/iio.h>
> > -#include <linux/iio/sysfs.h>
> > -
> > -/*
> > - * AD7816 config masks
> > - */
> > -#define AD7816_FULL			0x1
> > -#define AD7816_PD			0x2
> > -#define AD7816_CS_MASK			0x7
> > -#define AD7816_CS_MAX			0x4
> > -
> > -/*
> > - * AD7816 temperature masks
> > - */
> > -#define AD7816_VALUE_OFFSET		6
> > -#define AD7816_BOUND_VALUE_BASE		0x8
> > -#define AD7816_BOUND_VALUE_MIN		-95
> > -#define AD7816_BOUND_VALUE_MAX		152
> > -#define AD7816_TEMP_FLOAT_OFFSET	2
> > -#define AD7816_TEMP_FLOAT_MASK		0x3
> > -
> > -/*
> > - * struct ad7816_chip_info - chip specific information
> > - */
> > -
> > -struct ad7816_chip_info {
> > -	kernel_ulong_t id;
> > -	struct spi_device *spi_dev;
> > -	struct gpio_desc *rdwr_pin;
> > -	struct gpio_desc *convert_pin;
> > -	struct gpio_desc *busy_pin;
> > -	struct mutex lock; /* protect device state during SPI transfers */
> > -	u8  oti_data[AD7816_CS_MAX + 1];
> > -	u8  channel_id;	/* 0 always be temperature */
> > -	u8  mode;
> > -};
> > -
> > -enum ad7816_type {
> > -	ID_AD7816,
> > -	ID_AD7817,
> > -	ID_AD7818,
> > -};
> > -
> > -/*
> > - * ad7816 data access by SPI
> > - */
> > -static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data)
> > -{
> > -	struct spi_device *spi_dev = chip->spi_dev;
> > -	int ret;
> > -	__be16 buf;
> > -
> > -	guard(mutex)(&chip->lock);
> > -
> > -	gpiod_set_value(chip->rdwr_pin, 1);
> > -	gpiod_set_value(chip->rdwr_pin, 0);
> > -	ret = spi_write_then_read(spi_dev, &chip->channel_id, sizeof(chip->channel_id), NULL, 0);
> > -	if (ret < 0) {
> > -		dev_err(&spi_dev->dev, "SPI channel setting error\n");
> > -		return ret;
> > -	}
> > -	gpiod_set_value(chip->rdwr_pin, 1);
> > -
> > -	if (chip->mode == AD7816_PD) { /* operating mode 2 */
> > -		gpiod_set_value(chip->convert_pin, 1);
> > -		gpiod_set_value(chip->convert_pin, 0);
> > -	} else { /* operating mode 1 */
> > -		gpiod_set_value(chip->convert_pin, 0);
> > -		gpiod_set_value(chip->convert_pin, 1);
> > -	}
> > -
> > -	if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
> > -		while (gpiod_get_value(chip->busy_pin))
> > -			cpu_relax();
> > -	}
> > -
> > -	gpiod_set_value(chip->rdwr_pin, 0);
> > -	gpiod_set_value(chip->rdwr_pin, 1);
> > -	ret = spi_write_then_read(spi_dev, NULL, 0, &buf, sizeof(buf));
> > -	if (ret < 0) {
> > -		dev_err(&spi_dev->dev, "SPI data read error\n");
> > -		return ret;
> > -	}
> > -
> > -	*data = be16_to_cpu(buf);
> > -
> > -	return ret;
> > -}
> > -
> > -static int ad7816_spi_write(struct ad7816_chip_info *chip, u8 data)
> > -{
> > -	struct spi_device *spi_dev = chip->spi_dev;
> > -	int ret;
> > -
> > -	guard(mutex)(&chip->lock);
> > -
> > -	gpiod_set_value(chip->rdwr_pin, 1);
> > -	gpiod_set_value(chip->rdwr_pin, 0);
> > -	ret = spi_write_then_read(spi_dev, &data, sizeof(data), NULL, 0);
> > -	if (ret < 0)
> > -		dev_err(&spi_dev->dev, "SPI oti data write error\n");
> > -
> > -	return ret;
> > -}
> > -
> > -static ssize_t ad7816_show_mode(struct device *dev,
> > -				struct device_attribute *attr,
> > -				char *buf)
> > -{
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > -	struct ad7816_chip_info *chip = iio_priv(indio_dev);
> > -
> > -	if (chip->mode)
> > -		return sysfs_emit(buf, "power-save\n");
> > -	return sysfs_emit(buf, "full\n");
> > -}
> > -
> > -static ssize_t ad7816_store_mode(struct device *dev,
> > -				 struct device_attribute *attr,
> > -				 const char *buf,
> > -				 size_t len)
> > -{
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > -	struct ad7816_chip_info *chip = iio_priv(indio_dev);
> > -
> > -	guard(mutex)(&chip->lock);
> > -
> > -	if (strcmp(buf, "full") == 0) {
> > -		gpiod_set_value(chip->rdwr_pin, 1);
> > -		chip->mode = AD7816_FULL;
> > -	} else {
> > -		gpiod_set_value(chip->rdwr_pin, 0);
> > -		chip->mode = AD7816_PD;
> > -	}
> > -
> > -	return len;
> > -}
> > -
> > -static IIO_DEVICE_ATTR(mode, 0644,
> > -		ad7816_show_mode,
> > -		ad7816_store_mode,
> > -		0);
> > -
> > -static ssize_t ad7816_show_available_modes(struct device *dev,
> > -					   struct device_attribute *attr,
> > -					   char *buf)
> > -{
> > -	return sysfs_emit(buf, "full\npower-save\n");
> > -}
> > -
> > -static IIO_DEVICE_ATTR(available_modes, 0444, ad7816_show_available_modes,
> > -			NULL, 0);
> > -
> > -static ssize_t ad7816_show_channel(struct device *dev,
> > -				   struct device_attribute *attr,
> > -				   char *buf)
> > -{
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > -	struct ad7816_chip_info *chip = iio_priv(indio_dev);
> > -
> > -	return sysfs_emit(buf, "%d\n", chip->channel_id);
> > -}
> > -
> > -static ssize_t ad7816_store_channel(struct device *dev,
> > -				    struct device_attribute *attr,
> > -				    const char *buf,
> > -				    size_t len)
> > -{
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > -	struct ad7816_chip_info *chip = iio_priv(indio_dev);
> > -	unsigned long data;
> > -	int ret;
> > -
> > -	ret = kstrtoul(buf, 10, &data);
> > -	if (ret)
> > -		return ret;
> > -
> > -	if (data > AD7816_CS_MAX && data != AD7816_CS_MASK) {
> > -		dev_err(&chip->spi_dev->dev, "Invalid channel id %lu for %s.\n",
> > -			data, indio_dev->name);
> > -		return -EINVAL;
> > -	} else if (strcmp(indio_dev->name, "ad7818") == 0 && data > 1) {
> > -		dev_err(&chip->spi_dev->dev,
> > -			"Invalid channel id %lu for ad7818.\n", data);
> > -		return -EINVAL;
> > -	} else if (strcmp(indio_dev->name, "ad7816") == 0 && data > 0) {
> > -		dev_err(&chip->spi_dev->dev,
> > -			"Invalid channel id %lu for ad7816.\n", data);
> > -		return -EINVAL;
> > -	}
> > -
> > -	guard(mutex)(&chip->lock);
> > -
> > -	chip->channel_id = data;
> > -
> > -	return len;
> > -}
> > -
> > -static IIO_DEVICE_ATTR(channel, 0644,
> > -		ad7816_show_channel,
> > -		ad7816_store_channel,
> > -		0);
> > -
> > -static ssize_t ad7816_show_value(struct device *dev,
> > -				 struct device_attribute *attr,
> > -				 char *buf)
> > -{
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > -	struct ad7816_chip_info *chip = iio_priv(indio_dev);
> > -	u16 data;
> > -	s8 value;
> > -	int ret;
> > -
> > -	ret = ad7816_spi_read(chip, &data);
> > -	if (ret)
> > -		return -EIO;
> > -
> > -	data >>= AD7816_VALUE_OFFSET;
> > -
> > -	if (chip->channel_id == 0) {
> > -		value = (s8)((data >> AD7816_TEMP_FLOAT_OFFSET) - 103);
> > -		data &= AD7816_TEMP_FLOAT_MASK;
> > -		if (value < 0)
> > -			data = BIT(AD7816_TEMP_FLOAT_OFFSET) - data;
> > -		return sysfs_emit(buf, "%d.%.2d\n", value, data * 25);
> > -	}
> > -	return sysfs_emit(buf, "%u\n", data);
> > -}
> > -
> > -static IIO_DEVICE_ATTR(value, 0444, ad7816_show_value, NULL, 0);
> > -
> > -static struct attribute *ad7816_attributes[] = {
> > -	&iio_dev_attr_available_modes.dev_attr.attr,
> > -	&iio_dev_attr_mode.dev_attr.attr,
> > -	&iio_dev_attr_channel.dev_attr.attr,
> > -	&iio_dev_attr_value.dev_attr.attr,
> > -	NULL,
> > -};
> > -
> > -static const struct attribute_group ad7816_attribute_group = {
> > -	.attrs = ad7816_attributes,
> > -};
> > -
> > -/*
> > - * temperature bound events
> > - */
> > -
> > -#define IIO_EVENT_CODE_AD7816_OTI IIO_UNMOD_EVENT_CODE(IIO_TEMP,	\
> > -						       0,		\
> > -						       IIO_EV_TYPE_THRESH, \
> > -						       IIO_EV_DIR_FALLING)
> > -
> > -static irqreturn_t ad7816_event_handler(int irq, void *private)
> > -{
> > -	iio_push_event(private, IIO_EVENT_CODE_AD7816_OTI,
> > -		       iio_get_time_ns(private));
> > -	return IRQ_HANDLED;
> > -}
> > -
> > -static ssize_t ad7816_show_oti(struct device *dev,
> > -			       struct device_attribute *attr,
> > -			       char *buf)
> > -{
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > -	struct ad7816_chip_info *chip = iio_priv(indio_dev);
> > -	int value;
> > -
> > -	if (chip->channel_id > AD7816_CS_MAX) {
> > -		dev_err(dev, "Invalid oti channel id %d.\n", chip->channel_id);
> > -		return -EINVAL;
> > -	} else if (chip->channel_id == 0) {
> > -		value = AD7816_BOUND_VALUE_MIN +
> > -			(chip->oti_data[chip->channel_id] -
> > -			AD7816_BOUND_VALUE_BASE);
> > -		return sysfs_emit(buf, "%d\n", value);
> > -	}
> > -	return sysfs_emit(buf, "%u\n", chip->oti_data[chip->channel_id]);
> > -}
> > -
> > -static inline ssize_t ad7816_set_oti(struct device *dev,
> > -				     struct device_attribute *attr,
> > -				     const char *buf,
> > -				     size_t len)
> > -{
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > -	struct ad7816_chip_info *chip = iio_priv(indio_dev);
> > -	long value;
> > -	u8 data;
> > -	int ret;
> > -
> > -	ret = kstrtol(buf, 10, &value);
> > -	if (ret)
> > -		return ret;
> > -
> > -	if (chip->channel_id > AD7816_CS_MAX) {
> > -		dev_err(dev, "Invalid oti channel id %d.\n", chip->channel_id);
> > -		return -EINVAL;
> > -	} else if (chip->channel_id == 0) {
> > -		if (value < AD7816_BOUND_VALUE_MIN ||
> > -		    value > AD7816_BOUND_VALUE_MAX)
> > -			return -EINVAL;
> > -
> > -		data = (u8)(value - AD7816_BOUND_VALUE_MIN +
> > -			AD7816_BOUND_VALUE_BASE);
> > -	} else {
> > -		if (value < AD7816_BOUND_VALUE_BASE || value > 255)
> > -			return -EINVAL;
> > -
> > -		data = (u8)value;
> > -	}
> > -
> > -	ret = ad7816_spi_write(chip, data);
> > -	if (ret)
> > -		return -EIO;
> > -
> > -	chip->oti_data[chip->channel_id] = data;
> > -
> > -	return len;
> > -}
> > -
> > -static IIO_DEVICE_ATTR(oti, 0644,
> > -		       ad7816_show_oti, ad7816_set_oti, 0);
> > -
> > -static struct attribute *ad7816_event_attributes[] = {
> > -	&iio_dev_attr_oti.dev_attr.attr,
> > -	NULL,
> > -};
> > -
> > -static const struct attribute_group ad7816_event_attribute_group = {
> > -	.attrs = ad7816_event_attributes,
> > -	.name = "events",
> > -};
> > -
> > -static const struct iio_info ad7816_info = {
> > -	.attrs = &ad7816_attribute_group,
> > -	.event_attrs = &ad7816_event_attribute_group,
> > -};
> > -
> > -/*
> > - * device probe and remove
> > - */
> > -
> > -static int ad7816_probe(struct spi_device *spi_dev)
> > -{
> > -	struct ad7816_chip_info *chip;
> > -	struct iio_dev *indio_dev;
> > -	int i, ret;
> > -
> > -	indio_dev = devm_iio_device_alloc(&spi_dev->dev, sizeof(*chip));
> > -	if (!indio_dev)
> > -		return -ENOMEM;
> > -	chip = iio_priv(indio_dev);
> > -
> > -	ret = devm_mutex_init(&spi_dev->dev, &chip->lock);
> > -	if (ret)
> > -		return ret;
> > -
> > -	chip->spi_dev = spi_dev;
> > -	for (i = 0; i <= AD7816_CS_MAX; i++)
> > -		chip->oti_data[i] = 203;
> > -
> > -	chip->id = spi_get_device_id(spi_dev)->driver_data;
> > -	chip->rdwr_pin = devm_gpiod_get(&spi_dev->dev, "rdwr", GPIOD_OUT_HIGH);
> > -	if (IS_ERR(chip->rdwr_pin)) {
> > -		ret = PTR_ERR(chip->rdwr_pin);
> > -		dev_err(&spi_dev->dev, "Failed to request rdwr GPIO: %d\n",
> > -			ret);
> > -		return ret;
> > -	}
> > -	chip->convert_pin = devm_gpiod_get(&spi_dev->dev, "convert",
> > -					   GPIOD_OUT_HIGH);
> > -	if (IS_ERR(chip->convert_pin)) {
> > -		ret = PTR_ERR(chip->convert_pin);
> > -		dev_err(&spi_dev->dev, "Failed to request convert GPIO: %d\n",
> > -			ret);
> > -		return ret;
> > -	}
> > -	if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
> > -		chip->busy_pin = devm_gpiod_get(&spi_dev->dev, "busy",
> > -						GPIOD_IN);
> > -		if (IS_ERR(chip->busy_pin)) {
> > -			ret = PTR_ERR(chip->busy_pin);
> > -			dev_err(&spi_dev->dev, "Failed to request busy GPIO: %d\n",
> > -				ret);
> > -			return ret;
> > -		}
> > -	}
> > -
> > -	indio_dev->name = spi_get_device_id(spi_dev)->name;
> > -	indio_dev->info = &ad7816_info;
> > -	indio_dev->modes = INDIO_DIRECT_MODE;
> > -
> > -	if (spi_dev->irq) {
> > -		/* Only low trigger is supported in ad7816/7/8 */
> > -		ret = devm_request_threaded_irq(&spi_dev->dev, spi_dev->irq,
> > -						NULL,
> > -						&ad7816_event_handler,
> > -						IRQF_TRIGGER_LOW | IRQF_ONESHOT,
> > -						indio_dev->name,
> > -						indio_dev);
> > -		if (ret)
> > -			return ret;
> > -	}
> > -
> > -	ret = devm_iio_device_register(&spi_dev->dev, indio_dev);
> > -	if (ret)
> > -		return ret;
> > -
> > -	dev_info(&spi_dev->dev, "%s temperature sensor and ADC registered.\n",
> > -		 indio_dev->name);
> > -
> > -	return 0;
> > -}
> > -
> > -static const struct of_device_id ad7816_of_match[] = {
> > -	{ .compatible = "adi,ad7816", },
> > -	{ .compatible = "adi,ad7817", },
> > -	{ .compatible = "adi,ad7818", },
> > -	{ }
> > -};
> > -MODULE_DEVICE_TABLE(of, ad7816_of_match);
> > -
> > -static const struct spi_device_id ad7816_id[] = {
> > -	{ .name = "ad7816", .driver_data = ID_AD7816 },
> > -	{ .name = "ad7817", .driver_data = ID_AD7817 },
> > -	{ .name = "ad7818", .driver_data = ID_AD7818 },
> > -	{ }
> > -};
> > -
> > -MODULE_DEVICE_TABLE(spi, ad7816_id);
> > -
> > -static struct spi_driver ad7816_driver = {
> > -	.driver = {
> > -		.name = "ad7816",
> > -		.of_match_table = ad7816_of_match,
> > -	},
> > -	.probe = ad7816_probe,
> > -	.id_table = ad7816_id,
> > -};
> > -module_spi_driver(ad7816_driver);
> > -
> > -MODULE_AUTHOR("Sonic Zhang <sonic.zhang@analog.com>");
> > -MODULE_DESCRIPTION("Analog Devices AD7816/7/8 digital temperature sensor driver");
> > -MODULE_LICENSE("GPL v2");
> > -- 
> > 2.47.3
> >