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* [PATCH] staging: iio: adc: ad7816: remove obsolete driver
@ 2026-10-06 11:51 Joshua Crofts
  2026-10-12 14:41 ` Nuno Sá
  0 siblings, 1 reply; 2+ messages in thread
From: Joshua Crofts @ 2026-10-06 11:51 UTC (permalink / raw)
  To: Jonathan Cameron, Greg Kroah-Hartman, David Lechner, Nuno Sá,
	Andy Shevchenko, Michael Hennerich
  Cc: linux-kernel, linux-iio, linux-staging, linux

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.

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].

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


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