iio: humidity: hts221: update probe and logging implementations

Replace the custom oversampling_ratio_available sysfs attributes with the standard IIO read_avail() callback. This lets the IIO core create and format *_available attributes and exposes the lists to in-kernel consumers.

Signed-off-by Adi Nata <[email protected]>

---
 drivers/iio/humidity/hts221_core.c | 106 +++++++++++------------------
 1 file changed, 40 insertions(+), 66 deletions(-)

drivers/iio/humidity/hts221_core.c +40 -66

index bfeb0a60d3af..76a391f421f5 100644
@@ -10,7 +10,6 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/device.h>
-#include <linux/iio/sysfs.h>
 #include <linux/delay.h>
 #include <linux/pm.h>
 #include <linux/regmap.h>

@@ -49,7 +48,7 @@ struct hts221_odr {
 struct hts221_avg {
 	u8 addr;
 	u8 mask;
-	u16 avg_avl[HTS221_AVG_DEPTH];
+	int avg_avl[HTS221_AVG_DEPTH];
 };
 
 static const struct hts221_odr hts221_odr_table[] = {

@@ -58,6 +57,8 @@ static const struct hts221_odr hts221_odr_table[] = {
 	{ 13, 0x03 },	/* 12.5Hz */
 };
 
+static const int hts221_odr_avail[] = { 1, 7, 13 };
+
 static const struct hts221_avg hts221_avg_list[] = {
 	{
 		.addr = 0x10,

@@ -97,7 +98,11 @@ static const struct iio_chan_spec hts221_channels[] = {
 				      BIT(IIO_CHAN_INFO_OFFSET) |
 				      BIT(IIO_CHAN_INFO_SCALE) |
 				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.info_mask_separate_available =
+				BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_all_available =
+				BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.scan_index = 0,
 		.scan_type = {
 			.sign = 's',

@@ -113,7 +118,11 @@ static const struct iio_chan_spec hts221_channels[] = {
 				      BIT(IIO_CHAN_INFO_OFFSET) |
 				      BIT(IIO_CHAN_INFO_SCALE) |
 				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.info_mask_separate_available =
+				BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_all_available =
+				BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.scan_index = 1,
 		.scan_type = {
 			.sign = 's',

@@ -192,53 +201,35 @@ static int hts221_update_avg(struct hts221_hw *hw,
 	return 0;
 }
 
-static ssize_t hts221_sysfs_sampling_freq(struct device *dev,
-					  struct device_attribute *attr,
-					  char *buf)
-{
-	int i;
-	ssize_t len = 0;
-
-	for (i = 0; i < ARRAY_SIZE(hts221_odr_table); i++)
-		len += scnprintf(buf + len, PAGE_SIZE - len, "%d ",
-				 hts221_odr_table[i].hz);
-	buf[len - 1] = '\n';
-
-	return len;
-}
-
-static ssize_t
-hts221_sysfs_rh_oversampling_avail(struct device *dev,
-				   struct device_attribute *attr,
-				   char *buf)
-{
-	const struct hts221_avg *avg = &hts221_avg_list[HTS221_SENSOR_H];
-	ssize_t len = 0;
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(avg->avg_avl); i++)
-		len += scnprintf(buf + len, PAGE_SIZE - len, "%d ",
-				 avg->avg_avl[i]);
-	buf[len - 1] = '\n';
-
-	return len;
-}
-
-static ssize_t
-hts221_sysfs_temp_oversampling_avail(struct device *dev,
-				     struct device_attribute *attr,
-				     char *buf)
+static int hts221_read_avail(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     const int **vals, int *type, int *length,
+			     long mask)
 {
-	const struct hts221_avg *avg = &hts221_avg_list[HTS221_SENSOR_T];
-	ssize_t len = 0;
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(avg->avg_avl); i++)
-		len += scnprintf(buf + len, PAGE_SIZE - len, "%d ",
-				 avg->avg_avl[i]);
-	buf[len - 1] = '\n';
-
-	return len;
+	switch (mask) {
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->type) {
+		case IIO_HUMIDITYRELATIVE:
+			*vals = hts221_avg_list[HTS221_SENSOR_H].avg_avl;
+			*length = ARRAY_SIZE(hts221_avg_list[HTS221_SENSOR_H].avg_avl);
+			break;
+		case IIO_TEMP:
+			*vals = hts221_avg_list[HTS221_SENSOR_T].avg_avl;
+			*length = ARRAY_SIZE(hts221_avg_list[HTS221_SENSOR_T].avg_avl);
+			break;
+		default:
+			return -EINVAL;
+		}
+		*type = IIO_VAL_INT;
+		return IIO_AVAIL_LIST;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*vals = hts221_odr_avail;
+		*type = IIO_VAL_INT;
+		*length = ARRAY_SIZE(hts221_odr_avail);
+		return IIO_AVAIL_LIST;
+	default:
+		return -EINVAL;
+	}
 }
 
 int hts221_set_enable(struct hts221_hw *hw, bool enable)

@@ -521,27 +512,10 @@ static int hts221_validate_trigger(struct iio_dev *iio_dev,
 	return hw->trig == trig ? 0 : -EINVAL;
 }
 
-static IIO_DEVICE_ATTR(in_humidity_oversampling_ratio_available, S_IRUGO,
-		       hts221_sysfs_rh_oversampling_avail, NULL, 0);
-static IIO_DEVICE_ATTR(in_temp_oversampling_ratio_available, S_IRUGO,
-		       hts221_sysfs_temp_oversampling_avail, NULL, 0);
-static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(hts221_sysfs_sampling_freq);
-
-static struct attribute *hts221_attributes[] = {
-	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
-	&iio_dev_attr_in_humidity_oversampling_ratio_available.dev_attr.attr,
-	&iio_dev_attr_in_temp_oversampling_ratio_available.dev_attr.attr,
-	NULL,
-};
-
-static const struct attribute_group hts221_attribute_group = {
-	.attrs = hts221_attributes,
-};
-
 static const struct iio_info hts221_info = {
-	.attrs = &hts221_attribute_group,
 	.read_raw = hts221_read_raw,
 	.write_raw = hts221_write_raw,
+	.read_avail = hts221_read_avail,
 	.validate_trigger = hts221_validate_trigger,
 };
 

Quoted 4 lines

Replace the custom oversampling_ratio_available sysfs attributes with the standard IIO read_avail() callback. This lets the IIO core create and format *_available attributes and exposes the lists to in-kernel consumers.

Sashiko points out that there is an ABI change in here as oddly the driver uses in_humidity_oversampling_ratio_available rather than in_humidityrelative_oversampling_ratio_available

Which makes this an ABI fix. Therefore this should have a fixes tag and be moved to the start of the set. Please check that logic though as maybe I'm missing something.

Hi Jonathan,

Thanks for the feedback. I have checked with what Sachiko is saying is correct. The custom attribute was in_humidity_oversampling_ratio_available while the current on is in_humidityrelative_oversampling_ratio_available because in industrial_core.c only has [IIO_HUMIDITYRELATIVE] = "humidityrelative".

For this humidity case in particular, would it be better to keep the legacy implementation while adding the new read_avail()?

The other case declaration will remain changed.

Quoted 13 lines

Quoted 4 lines

Replace the custom oversampling_ratio_available sysfs attributes with the standard IIO read_avail() callback. This lets the IIO core create and format *_available attributes and exposes the lists to in-kernel consumers.

Sashiko points out that there is an ABI change in here as oddly the driver uses in_humidity_oversampling_ratio_available rather than in_humidityrelative_oversampling_ratio_available

Which makes this an ABI fix. Therefore this should have a fixes tag and be moved to the start of the set. Please check that logic though as maybe I'm missing something.

Quoted 2 lines

For this humidity case in particular, would it be better to keep the legacy implementation while adding the new read_avail()?

To me it seems vanishingly unlikely there is any code out there jumping through the hoops to read the wrong ABI element to figure out a possible value to write to in_humidityrelative_oversampling_ratio

So I think this is in the category of ABI that we can change as long as no one notices. For IIO I will also generally take ABI fixes on basis we actually want to know if anyone is using the broken ABI (and they very rarely are!)

Hi Jonathan,
Thanks for the input. In this case, we can proceed with the current implementation?

Quoted 12 lines

Quoted 3 lines

For this humidity case in particular, would it be better to keep the legacy implementation while adding the new read_avail()?

To me it seems vanishingly unlikely there is any code out there jumping through the hoops to read the wrong ABI element to figure out a possible value to write to in_humidityrelative_oversampling_ratio

So I think this is in the category of ABI that we can change as long as no one notices. For IIO I will also generally take ABI fixes on basis we actually want to know if anyone is using the broken ABI (and they very rarely are!)

Quoted 4 lines

Replace the custom oversampling_ratio_available sysfs attributes with the standard IIO read_avail() callback. This lets the IIO core create and format *_available attributes and exposes the lists to in-kernel consumers.

Sashiko points out that there is an ABI change in here as oddly the driver uses in_humidity_oversampling_ratio_available rather than in_humidityrelative_oversampling_ratio_available

Which makes this an ABI fix. Therefore this should have a fixes tag and be moved to the start of the set. Please check that logic though as maybe I'm missing something.

Quoted 4 lines · On Sat, 8 Aug 2026 17:00:22 +0800 Adi Nata…

Replace the custom oversampling_ratio_available sysfs attributes with the standard IIO read_avail() callback. This lets the IIO core create and format *_available attributes and exposes the lists to in-kernel consumers.

Sashiko points out that there is an ABI change in here as oddly the driver uses in_humidity_oversampling_ratio_available rather than in_humidityrelative_oversampling_ratio_available

Which makes this an ABI fix. Therefore this should have a fixes tag and be moved to the start of the set. Please check that logic though as maybe I'm missing something.

J

Quoted 171 lines

Signed-off-by Adi Nata <[email protected]>

---
 drivers/iio/humidity/hts221_core.c | 106 +++++++++++------------------
 1 file changed, 40 insertions(+), 66 deletions(-)

drivers/iio/humidity/hts221_core.c +40 -66

index bfeb0a60d3af..76a391f421f5 100644
@@ -10,7 +10,6 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/device.h>
-#include <linux/iio/sysfs.h>
 #include <linux/delay.h>
 #include <linux/pm.h>
 #include <linux/regmap.h>

@@ -49,7 +48,7 @@ struct hts221_odr {
 struct hts221_avg {
      u8 addr;
      u8 mask;
-     u16 avg_avl[HTS221_AVG_DEPTH];
+     int avg_avl[HTS221_AVG_DEPTH];
 };
 
 static const struct hts221_odr hts221_odr_table[] = {

@@ -58,6 +57,8 @@ static const struct hts221_odr hts221_odr_table[] = {
      { 13, 0x03 },   /* 12.5Hz */
 };
 
+static const int hts221_odr_avail[] = { 1, 7, 13 };
+
 static const struct hts221_avg hts221_avg_list[] = {
      {
              .addr = 0x10,

@@ -97,7 +98,11 @@ static const struct iio_chan_spec hts221_channels[] = {
                                    BIT(IIO_CHAN_INFO_OFFSET) |
                                    BIT(IIO_CHAN_INFO_SCALE) |
                                    BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+             .info_mask_separate_available =
+                             BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
              .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+             .info_mask_shared_by_all_available =
+                             BIT(IIO_CHAN_INFO_SAMP_FREQ),
              .scan_index = 0,
              .scan_type = {
                      .sign = 's',

@@ -113,7 +118,11 @@ static const struct iio_chan_spec hts221_channels[] = {
                                    BIT(IIO_CHAN_INFO_OFFSET) |
                                    BIT(IIO_CHAN_INFO_SCALE) |
                                    BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+             .info_mask_separate_available =
+                             BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
              .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+             .info_mask_shared_by_all_available =
+                             BIT(IIO_CHAN_INFO_SAMP_FREQ),
              .scan_index = 1,
              .scan_type = {
                      .sign = 's',

@@ -192,53 +201,35 @@ static int hts221_update_avg(struct hts221_hw *hw,
      return 0;
 }
 
-static ssize_t hts221_sysfs_sampling_freq(struct device *dev,
-                                       struct device_attribute *attr,
-                                       char *buf)
-{
-     int i;
-     ssize_t len = 0;
-
-     for (i = 0; i < ARRAY_SIZE(hts221_odr_table); i++)
-             len += scnprintf(buf + len, PAGE_SIZE - len, "%d ",
-                              hts221_odr_table[i].hz);
-     buf[len - 1] = '\n';
-
-     return len;
-}
-
-static ssize_t
-hts221_sysfs_rh_oversampling_avail(struct device *dev,
-                                struct device_attribute *attr,
-                                char *buf)
-{
-     const struct hts221_avg *avg = &hts221_avg_list[HTS221_SENSOR_H];
-     ssize_t len = 0;
-     int i;
-
-     for (i = 0; i < ARRAY_SIZE(avg->avg_avl); i++)
-             len += scnprintf(buf + len, PAGE_SIZE - len, "%d ",
-                              avg->avg_avl[i]);
-     buf[len - 1] = '\n';
-
-     return len;
-}
-
-static ssize_t
-hts221_sysfs_temp_oversampling_avail(struct device *dev,
-                                  struct device_attribute *attr,
-                                  char *buf)
+static int hts221_read_avail(struct iio_dev *indio_dev,
+                          struct iio_chan_spec const *chan,
+                          const int **vals, int *type, int *length,
+                          long mask)
 {
-     const struct hts221_avg *avg = &hts221_avg_list[HTS221_SENSOR_T];
-     ssize_t len = 0;
-     int i;
-
-     for (i = 0; i < ARRAY_SIZE(avg->avg_avl); i++)
-             len += scnprintf(buf + len, PAGE_SIZE - len, "%d ",
-                              avg->avg_avl[i]);
-     buf[len - 1] = '\n';
-
-     return len;
+     switch (mask) {
+     case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+             switch (chan->type) {
+             case IIO_HUMIDITYRELATIVE:
+                     *vals = hts221_avg_list[HTS221_SENSOR_H].avg_avl;
+                     *length = ARRAY_SIZE(hts221_avg_list[HTS221_SENSOR_H].avg_avl);
+                     break;
+             case IIO_TEMP:
+                     *vals = hts221_avg_list[HTS221_SENSOR_T].avg_avl;
+                     *length = ARRAY_SIZE(hts221_avg_list[HTS221_SENSOR_T].avg_avl);
+                     break;
+             default:
+                     return -EINVAL;
+             }
+             *type = IIO_VAL_INT;
+             return IIO_AVAIL_LIST;
+     case IIO_CHAN_INFO_SAMP_FREQ:
+             *vals = hts221_odr_avail;
+             *type = IIO_VAL_INT;
+             *length = ARRAY_SIZE(hts221_odr_avail);
+             return IIO_AVAIL_LIST;
+     default:
+             return -EINVAL;
+     }
 }
 
 int hts221_set_enable(struct hts221_hw *hw, bool enable)

@@ -521,27 +512,10 @@ static int hts221_validate_trigger(struct iio_dev *iio_dev,
      return hw->trig == trig ? 0 : -EINVAL;
 }
 
-static IIO_DEVICE_ATTR(in_humidity_oversampling_ratio_available, S_IRUGO,
-                    hts221_sysfs_rh_oversampling_avail, NULL, 0);
-static IIO_DEVICE_ATTR(in_temp_oversampling_ratio_available, S_IRUGO,
-                    hts221_sysfs_temp_oversampling_avail, NULL, 0);
-static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(hts221_sysfs_sampling_freq);
-
-static struct attribute *hts221_attributes[] = {
-     &iio_dev_attr_sampling_frequency_available.dev_attr.attr,
-     &iio_dev_attr_in_humidity_oversampling_ratio_available.dev_attr.attr,
-     &iio_dev_attr_in_temp_oversampling_ratio_available.dev_attr.attr,
-     NULL,
-};
-
-static const struct attribute_group hts221_attribute_group = {
-     .attrs = hts221_attributes,
-};
-
 static const struct iio_info hts221_info = {
-     .attrs = &hts221_attribute_group,
      .read_raw = hts221_read_raw,
      .write_raw = hts221_write_raw,
+     .read_avail = hts221_read_avail,
      .validate_trigger = hts221_validate_trigger,
 };
 

Improve code readability per checkpatch warning

The WHOAMI check currently returns -ENODEV when the chip ID is not 0xbc. That rejects Device Tree fallback compatibles.

Keep failing if the WHOAMI register cannot be read. On an unexpected ID, log it and continue so OF fallback matching can work.

Use dev_err_probe() for the read-failure path.

static int hts221_check_whoami(struct hts221_hw *hw)

int err, data;

Convert remaining probe-time error logs to dev_err_probe() so the errno is included and deferred probe failures stay quiet.

Why hw->dev and not simply dev?!
Also in all cases.