Convert the ads7871 driver from the legacy hwmon_device_register() to the
modern hwmon_device_register_with_info() API. This migration simplifies
the driver by using the structured hwmon_channel_info approach and
prepares the codebase for the transition to a shared DMA-safe buffer.

Signed-off-by: Tabrez Ahmed <tabreztalks@gmail.com>
---
 drivers/hwmon/ads7871.c | 76 ++++++++++++++++++++++-------------------
 1 file changed, 41 insertions(+), 35 deletions(-)

diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
index 9bfdf9e6bcd77..41a1e9bbd4050 100644
--- a/drivers/hwmon/ads7871.c
+++ b/drivers/hwmon/ads7871.c
@@ -56,7 +56,6 @@
 #include <linux/init.h>
 #include <linux/spi/spi.h>
 #include <linux/hwmon.h>
-#include <linux/hwmon-sysfs.h>
 #include <linux/err.h>
 #include <linux/delay.h>
 
@@ -65,10 +64,20 @@
 struct ads7871_data {
 	struct spi_device *spi;
 };
+static umode_t ads7871_is_visible(const void *data,
+				  enum hwmon_sensor_types type,
+				  u32 attr, int channel)
+{
+	if (type == hwmon_in && attr == hwmon_in_input)
+		return 0444;
+
+	return 0;
+}
 
 static int ads7871_read_reg8(struct spi_device *spi, int reg)
 {
 	int ret;
+
 	reg = reg | INST_READ_BM;
 	ret = spi_w8r8(spi, reg);
 	return ret;
@@ -77,6 +86,7 @@ static int ads7871_read_reg8(struct spi_device *spi, int reg)
 static int ads7871_read_reg16(struct spi_device *spi, int reg)
 {
 	int ret;
+
 	reg = reg | INST_READ_BM | INST_16BIT_BM;
 	ret = spi_w8r16(spi, reg);
 	return ret;
@@ -85,19 +95,20 @@ static int ads7871_read_reg16(struct spi_device *spi, int reg)
 static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
 {
 	u8 tmp[2] = {reg, val};
+
 	return spi_write(spi, tmp, sizeof(tmp));
 }
 
-static ssize_t voltage_show(struct device *dev, struct device_attribute *da,
-			    char *buf)
+static int ads7871_read(struct device *dev, enum hwmon_sensor_types type,
+			u32 attr, int channel, long *val)
 {
 	struct ads7871_data *pdata = dev_get_drvdata(dev);
 	struct spi_device *spi = pdata->spi;
-	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
-	int ret, val, i = 0;
-	uint8_t channel, mux_cnv;
+	int ret, raw_val, i = 0;
+	uint8_t mux_cnv;
 
-	channel = attr->index;
+	if (type != hwmon_in || attr != hwmon_in_input)
+		return -EOPNOTSUPP;
 	/*
 	 * TODO: add support for conversions
 	 * other than single ended with a gain of 1
@@ -127,39 +138,34 @@ static ssize_t voltage_show(struct device *dev, struct device_attribute *da,
 	}
 
 	if (mux_cnv == 0) {
-		val = ads7871_read_reg16(spi, REG_LS_BYTE);
-		if (val < 0)
-			return val;
+		raw_val = ads7871_read_reg16(spi, REG_LS_BYTE);
+		if (raw_val < 0)
+			return raw_val;
+
 		/*result in volts*10000 = (val/8192)*2.5*10000*/
-		val = ((val >> 2) * 25000) / 8192;
-		return sysfs_emit(buf, "%d\n", val);
+		*val = ((raw_val >> 2) * 25000) / 8192;
+		return 0;
 	}
 
 	return -ETIMEDOUT;
 }
 
-static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0);
-static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1);
-static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2);
-static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3);
-static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4);
-static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5);
-static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6);
-static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7);
-
-static struct attribute *ads7871_attrs[] = {
-	&sensor_dev_attr_in0_input.dev_attr.attr,
-	&sensor_dev_attr_in1_input.dev_attr.attr,
-	&sensor_dev_attr_in2_input.dev_attr.attr,
-	&sensor_dev_attr_in3_input.dev_attr.attr,
-	&sensor_dev_attr_in4_input.dev_attr.attr,
-	&sensor_dev_attr_in5_input.dev_attr.attr,
-	&sensor_dev_attr_in6_input.dev_attr.attr,
-	&sensor_dev_attr_in7_input.dev_attr.attr,
+static const struct hwmon_channel_info * const ads7871_info[] = {
+	HWMON_CHANNEL_INFO(in,
+		HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT,
+		HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT),
 	NULL
 };
 
-ATTRIBUTE_GROUPS(ads7871);
+static const struct hwmon_ops ads7871_hwmon_ops = {
+	.is_visible = ads7871_is_visible,
+	.read = ads7871_read,
+};
+
+static const struct hwmon_chip_info ads7871_chip_info = {
+	.ops = &ads7871_hwmon_ops,
+	.info = ads7871_info,
+};
 
 static int ads7871_probe(struct spi_device *spi)
 {
@@ -194,10 +200,10 @@ static int ads7871_probe(struct spi_device *spi)
 		return -ENOMEM;
 
 	pdata->spi = spi;
-
-	hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
-							   pdata,
-							   ads7871_groups);
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, spi->modalias,
+							 pdata,
+							 &ads7871_chip_info,
+							 NULL);
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }
 
-- 
2.43.0

Hi,

On 3/29/26 00:33, Tabrez Ahmed wrote:
> Convert the ads7871 driver from the legacy hwmon_device_register() to the
> modern hwmon_device_register_with_info() API. This migration simplifies
> the driver by using the structured hwmon_channel_info approach and
> prepares the codebase for the transition to a shared DMA-safe buffer.
> 

Please add: "While at it, fix checkpatch violations" since you fixed the
"empty line after variable declarations" problem.

.. but please fix all of them. See inline.

Thanks,
Guenter

> Signed-off-by: Tabrez Ahmed <tabreztalks@gmail.com>
> ---
>   drivers/hwmon/ads7871.c | 76 ++++++++++++++++++++++-------------------
>   1 file changed, 41 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
> index 9bfdf9e6bcd77..41a1e9bbd4050 100644
> --- a/drivers/hwmon/ads7871.c
> +++ b/drivers/hwmon/ads7871.c
> @@ -56,7 +56,6 @@
>   #include <linux/init.h>
>   #include <linux/spi/spi.h>
>   #include <linux/hwmon.h>
> -#include <linux/hwmon-sysfs.h>
>   #include <linux/err.h>
>   #include <linux/delay.h>
>   
> @@ -65,10 +64,20 @@
>   struct ads7871_data {
>   	struct spi_device *spi;
>   };

Add empty line (checkpatch reports that, plus a couple more formatting issues).

> +static umode_t ads7871_is_visible(const void *data,
> +				  enum hwmon_sensor_types type,
> +				  u32 attr, int channel)
> +{
> +	if (type == hwmon_in && attr == hwmon_in_input)
> +		return 0444;
> +
> +	return 0;
> +}
>   
>   static int ads7871_read_reg8(struct spi_device *spi, int reg)
>   {
>   	int ret;
> +
>   	reg = reg | INST_READ_BM;
>   	ret = spi_w8r8(spi, reg);
>   	return ret;
> @@ -77,6 +86,7 @@ static int ads7871_read_reg8(struct spi_device *spi, int reg)
>   static int ads7871_read_reg16(struct spi_device *spi, int reg)
>   {
>   	int ret;
> +
>   	reg = reg | INST_READ_BM | INST_16BIT_BM;
>   	ret = spi_w8r16(spi, reg);
>   	return ret;
> @@ -85,19 +95,20 @@ static int ads7871_read_reg16(struct spi_device *spi, int reg)
>   static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
>   {
>   	u8 tmp[2] = {reg, val};
> +
>   	return spi_write(spi, tmp, sizeof(tmp));
>   }
>   
> -static ssize_t voltage_show(struct device *dev, struct device_attribute *da,
> -			    char *buf)
> +static int ads7871_read(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long *val)
>   {
>   	struct ads7871_data *pdata = dev_get_drvdata(dev);
>   	struct spi_device *spi = pdata->spi;
> -	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> -	int ret, val, i = 0;
> -	uint8_t channel, mux_cnv;
> +	int ret, raw_val, i = 0;
> +	uint8_t mux_cnv;
>   
> -	channel = attr->index;
> +	if (type != hwmon_in || attr != hwmon_in_input)
> +		return -EOPNOTSUPP;

That doesn't hurt but isn't really needed here.

>   	/*
>   	 * TODO: add support for conversions
>   	 * other than single ended with a gain of 1
> @@ -127,39 +138,34 @@ static ssize_t voltage_show(struct device *dev, struct device_attribute *da,
>   	}
>   
>   	if (mux_cnv == 0) {
> -		val = ads7871_read_reg16(spi, REG_LS_BYTE);
> -		if (val < 0)
> -			return val;
> +		raw_val = ads7871_read_reg16(spi, REG_LS_BYTE);
> +		if (raw_val < 0)
> +			return raw_val;
> +
>   		/*result in volts*10000 = (val/8192)*2.5*10000*/
> -		val = ((val >> 2) * 25000) / 8192;
> -		return sysfs_emit(buf, "%d\n", val);
> +		*val = ((raw_val >> 2) * 25000) / 8192;
> +		return 0;

Sashiko suggests to make the 16-bit operations endianness safe.

https://sashiko.dev/#/patchset/20260329073352.270451-1-tabreztalks%40gmail.com

Not mandatory, but just in case you have the time ...

>   	}
>   
>   	return -ETIMEDOUT;
>   }
>   
> -static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0);
> -static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1);
> -static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2);
> -static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3);
> -static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4);
> -static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5);
> -static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6);
> -static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7);
> -
> -static struct attribute *ads7871_attrs[] = {
> -	&sensor_dev_attr_in0_input.dev_attr.attr,
> -	&sensor_dev_attr_in1_input.dev_attr.attr,
> -	&sensor_dev_attr_in2_input.dev_attr.attr,
> -	&sensor_dev_attr_in3_input.dev_attr.attr,
> -	&sensor_dev_attr_in4_input.dev_attr.attr,
> -	&sensor_dev_attr_in5_input.dev_attr.attr,
> -	&sensor_dev_attr_in6_input.dev_attr.attr,
> -	&sensor_dev_attr_in7_input.dev_attr.attr,
> +static const struct hwmon_channel_info * const ads7871_info[] = {
> +	HWMON_CHANNEL_INFO(in,
> +		HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT,
> +		HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT),
>   	NULL
>   };
>   
> -ATTRIBUTE_GROUPS(ads7871);
> +static const struct hwmon_ops ads7871_hwmon_ops = {
> +	.is_visible = ads7871_is_visible,
> +	.read = ads7871_read,
> +};
> +
> +static const struct hwmon_chip_info ads7871_chip_info = {
> +	.ops = &ads7871_hwmon_ops,
> +	.info = ads7871_info,
> +};
>   
>   static int ads7871_probe(struct spi_device *spi)
>   {
> @@ -194,10 +200,10 @@ static int ads7871_probe(struct spi_device *spi)
>   		return -ENOMEM;
>   
>   	pdata->spi = spi;
> -
> -	hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
> -							   pdata,
> -							   ads7871_groups);
> +	hwmon_dev = devm_hwmon_device_register_with_info(dev, spi->modalias,
> +							 pdata,
> +							 &ads7871_chip_info,
> +							 NULL);
>   	return PTR_ERR_OR_ZERO(hwmon_dev);
>   }
>