[PATCH v2 2/2] hwmon: iio: Add labels from IIO channels

Sean Anderson
2024-06-24T17:46:28Z

Add labels from IIO channels to our channels. This allows userspace to
display more meaningful names instead of "in0" or "temp5".

Although lm-sensors gracefully handles errors when reading channel
labels, the ABI says the label attribute

> Should only be created if the driver has hints about what this voltage
> channel is being used for, and user-space doesn't.

Therefore, we test to see if the channel has a label before
creating the attribute.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

Changes in v2:
- Check if the label exists before creating the attribute

drivers/hwmon/iio_hwmon.c | 45 ++++++++++++++++++++++++++++++++++-----
1 file changed, 40 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/iio_hwmon.c b/drivers/hwmon/iio_hwmon.c
index 4c8a80847891..5722cb9d81f9 100644
--- a/drivers/hwmon/iio_hwmon.c
+++ b/drivers/hwmon/iio_hwmon.c
@@ -33,6 +33,17 @@ struct iio_hwmon_state {
struct attribute **attrs;
};

+static ssize_t iio_hwmon_read_label(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
+ struct iio_hwmon_state *state = dev_get_drvdata(dev);
+ struct iio_channel *chan = &state->channels[sattr->index];
+
+ return iio_read_channel_label(chan, buf);
+}
+
/*
* Assumes that IIO and hwmon operate in the same base units.
* This is supposed to be true, but needs verification for
@@ -68,12 +79,13 @@ static int iio_hwmon_probe(struct platform_device *pdev)
struct device *dev = &pdev->dev;
struct iio_hwmon_state *st;
struct sensor_device_attribute *a;
- int ret, i;
+ int ret, i, attr = 0;
int in_i = 1, temp_i = 1, curr_i = 1, humidity_i = 1, power_i = 1;
enum iio_chan_type type;
struct iio_channel *channels;
struct device *hwmon_dev;
char *sname;
+ void *buf;

channels = devm_iio_channel_get_all(dev);
if (IS_ERR(channels)) {
@@ -85,17 +97,18 @@ static int iio_hwmon_probe(struct platform_device *pdev)
}

st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
- if (st == NULL)
+ buf = (void *)devm_get_free_pages(dev, GFP_KERNEL, 0);
+ if (!st || !buf)
return -ENOMEM;

st->channels = channels;

- /* count how many attributes we have */
+ /* count how many channels we have */
while (st->channels[st->num_channels].indio_dev)
st->num_channels++;

st->attrs = devm_kcalloc(dev,
- st->num_channels + 1, sizeof(*st->attrs),
+ 2 * st->num_channels + 1, sizeof(*st->attrs),
GFP_KERNEL);
if (st->attrs == NULL)
return -ENOMEM;
@@ -147,9 +160,31 @@ static int iio_hwmon_probe(struct platform_device *pdev)
a->dev_attr.show = iio_hwmon_read_val;
a->dev_attr.attr.mode = 0444;
a->index = i;
- st->attrs[i] = &a->dev_attr.attr;
+ st->attrs[attr++] = &a->dev_attr.attr;
+
+ /* Let's see if we have a label... */
+ if (iio_read_channel_label(&st->channels[i], buf) < 0)
+ continue;
+
+ a = devm_kzalloc(dev, sizeof(*a), GFP_KERNEL);
+ if (a == NULL)
+ return -ENOMEM;
+
+ sysfs_attr_init(&a->dev_attr.attr);
+ a->dev_attr.attr.name = devm_kasprintf(dev, GFP_KERNEL,
+ "%s%d_label",
+ prefix, n);
+ if (!a->dev_attr.attr.name)
+ return -ENOMEM;
+
+ a->dev_attr.show = iio_hwmon_read_label;
+ a->dev_attr.attr.mode = 0444;
+ a->index = i;
+ st->attrs[attr++] = &a->dev_attr.attr;
}

+ devm_free_pages(dev, (unsigned long)buf);
+
st->attr_group.attrs = st->attrs;
st->groups[0] = &st->attr_group;

--
2.35.1.1320.gc452695387.dirty