iio: event: add optional event label support

This adds a new optional field to struct iio_info to allow drivers to
specify a label for the event. This is useful for cases where there are
many events or the event attribute name is not descriptive enough or
where an event doesn't have any other attributes.

The implementation is based on the existing label support for channels.
So either all events of a device have a label attribute or none do.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231005-ad2s1210-mainline-v4-12-ec00746840fc@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

2 files changed, 63 insertions, 0 deletions

diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
index 19f7a91157ee..910c1f14abd5 100644
--- a/drivers/iio/industrialio-event.c
+++ b/drivers/iio/industrialio-event.c
@@ -355,6 +355,21 @@ static ssize_t iio_ev_value_store(struct device *dev,
 	return len;
 }
 
+static ssize_t iio_ev_label_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+
+	if (indio_dev->info->read_event_label)
+		return indio_dev->info->read_event_label(indio_dev,
+				 this_attr->c, iio_ev_attr_type(this_attr),
+				 iio_ev_attr_dir(this_attr), buf);
+
+	return -EINVAL;
+}
+
 static int iio_device_add_event(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan, unsigned int spec_index,
 	enum iio_event_type type, enum iio_event_direction dir,
@@ -411,6 +426,41 @@ static int iio_device_add_event(struct iio_dev *indio_dev,
 	return attrcount;
 }
 
+static int iio_device_add_event_label(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan,
+				      unsigned int spec_index,
+				      enum iio_event_type type,
+				      enum iio_event_direction dir)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	char *postfix;
+	int ret;
+
+	if (!indio_dev->info->read_event_label)
+		return 0;
+
+	if (dir != IIO_EV_DIR_NONE)
+		postfix = kasprintf(GFP_KERNEL, "%s_%s_label",
+				iio_ev_type_text[type],
+				iio_ev_dir_text[dir]);
+	else
+		postfix = kasprintf(GFP_KERNEL, "%s_label",
+				iio_ev_type_text[type]);
+	if (postfix == NULL)
+		return -ENOMEM;
+
+	ret = __iio_add_chan_devattr(postfix, chan, &iio_ev_label_show, NULL,
+				spec_index, IIO_SEPARATE, &indio_dev->dev, NULL,
+				&iio_dev_opaque->event_interface->dev_attr_list);
+
+	kfree(postfix);
+
+	if (ret < 0)
+		return ret;
+
+	return 1;
+}
+
 static int iio_device_add_event_sysfs(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan)
 {
@@ -448,6 +498,11 @@ static int iio_device_add_event_sysfs(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 		attrcount += ret;
+
+		ret = iio_device_add_event_label(indio_dev, chan, i, type, dir);
+		if (ret < 0)
+			return ret;
+		attrcount += ret;
 	}
 	ret = attrcount;
 	return ret;
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 7bfa1b9bc8a2..d0ce3b71106a 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -427,6 +427,8 @@ struct iio_trigger; /* forward declaration */
  * @write_event_config:	set if the event is enabled.
  * @read_event_value:	read a configuration value associated with the event.
  * @write_event_value:	write a configuration value for the event.
+ * @read_event_label:	function to request label name for a specified label,
+ *			for better event identification.
  * @validate_trigger:	function to validate the trigger when the
  *			current trigger gets changed.
  * @update_scan_mode:	function to configure device and scan buffer when
@@ -511,6 +513,12 @@ struct iio_info {
 				 enum iio_event_direction dir,
 				 enum iio_event_info info, int val, int val2);
 
+	int (*read_event_label)(struct iio_dev *indio_dev,
+				struct iio_chan_spec const *chan,
+				enum iio_event_type type,
+				enum iio_event_direction dir,
+				char *label);
+
 	int (*validate_trigger)(struct iio_dev *indio_dev,
 				struct iio_trigger *trig);
 	int (*update_scan_mode)(struct iio_dev *indio_dev,