iio: core: Add optional symbolic label to device attributes

If a label is defined in the device tree for this device add that
to the device specific attributes. This is useful for userspace to
be able to identify an individual device when multiple identical
chips are present in the system.
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -1238,6 +1238,16 @@ static ssize_t iio_show_dev_name(struct device *dev,
 
 static DEVICE_ATTR(name, S_IRUGO, iio_show_dev_name, NULL);
 
+static ssize_t iio_show_dev_label(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	return snprintf(buf, PAGE_SIZE, "%s\n", indio_dev->label);
+}
+
+static DEVICE_ATTR(label, S_IRUGO, iio_show_dev_label, NULL);
+
 static ssize_t iio_show_timestamp_clock(struct device *dev,
 					struct device_attribute *attr,
 					char *buf)
@@ -1354,6 +1364,8 @@ static int iio_device_register_sysfs(struct iio_dev *indio_dev)
 
 	if (indio_dev->name)
 		attrcount++;
+	if (indio_dev->label)
+		attrcount++;
 	if (clk)
 		attrcount++;
 
@@ -1376,6 +1388,8 @@ static int iio_device_register_sysfs(struct iio_dev *indio_dev)
 		indio_dev->chan_attr_group.attrs[attrn++] = &p->dev_attr.attr;
 	if (indio_dev->name)
 		indio_dev->chan_attr_group.attrs[attrn++] = &dev_attr_name.attr;
+	if (indio_dev->label)
+		indio_dev->chan_attr_group.attrs[attrn++] = &dev_attr_label.attr;
 	if (clk)
 		indio_dev->chan_attr_group.attrs[attrn++] = clk;
 
@@ -1647,6 +1661,9 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
 	if (!indio_dev->dev.of_node && indio_dev->dev.parent)
 		indio_dev->dev.of_node = indio_dev->dev.parent->of_node;
 
+	indio_dev->label = of_get_property(indio_dev->dev.of_node, "label",
+					   NULL);
+
 	ret = iio_check_unique_scan_index(indio_dev);
 	if (ret < 0)
 		return ret;

include/linux/iio/iio.h

@@ -510,6 +510,7 @@ struct iio_buffer_setup_ops {
  *			attributes
  * @chan_attr_group:	[INTERN] group for all attrs in base directory
  * @name:		[DRIVER] name of the device.
+ * @label:              [DRIVER] unique name to identify which device this is
  * @info:		[DRIVER] callbacks and constant info from driver
  * @clock_id:		[INTERN] timestamping clock posix identifier
  * @info_exist_lock:	[INTERN] lock to prevent use during removal
@@ -553,6 +554,7 @@ struct iio_dev {
 	struct list_head		channel_attr_list;
 	struct attribute_group		chan_attr_group;
 	const char			*name;
+	const char			*label;
 	const struct iio_info		*info;
 	clockid_t			clock_id;
 	struct mutex			info_exist_lock;