iio: core: Add optional symbolic label to a device channel

If a label is defined in the device tree for this channel add that
to the channel specific attributes. This is useful for userspace to
be able to identify an individual channel.

Signed-off-by: Cristian Pop <cristian.pop@analog.com>
Link: https://lore.kernel.org/r/20200928090959.88842-1-cristian.pop@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 9955672fc16ae85990bf3830a6063bc2ee7b8338..0402be441ffb5a9adb4fc4f0b44e101eb4872b32 100644 (file)
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -673,6 +673,19 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
 }
 EXPORT_SYMBOL_GPL(iio_format_value);
 
+static ssize_t iio_read_channel_label(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_label)
+               return -EINVAL;
+
+       return indio_dev->info->read_label(indio_dev, this_attr->c, buf);
+}
+
 static ssize_t iio_read_channel_info(struct device *dev,
                                     struct device_attribute *attr,
                                     char *buf)
@@ -1141,6 +1154,29 @@ error_iio_dev_attr_free:
        return ret;
 }
 
+static int iio_device_add_channel_label(struct iio_dev *indio_dev,
+                                        struct iio_chan_spec const *chan)
+{
+       struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+       int ret;
+
+       if (!indio_dev->info->read_label)
+               return 0;
+
+       ret = __iio_add_chan_devattr("label",
+                                    chan,
+                                    &iio_read_channel_label,
+                                    NULL,
+                                    0,
+                                    IIO_SEPARATE,
+                                    &indio_dev->dev,
+                                    &iio_dev_opaque->channel_attr_list);
+       if (ret < 0)
+               return ret;
+
+       return 1;
+}
+
 static int iio_device_add_info_mask_type(struct iio_dev *indio_dev,
                                         struct iio_chan_spec const *chan,
                                         enum iio_shared_by shared_by,
@@ -1274,6 +1310,11 @@ static int iio_device_add_channel_sysfs(struct iio_dev *indio_dev,
                return ret;
        attrcount += ret;
 
+       ret = iio_device_add_channel_label(indio_dev, chan);
+       if (ret < 0)
+               return ret;
+       attrcount += ret;
+
        if (chan->ext_info) {
                unsigned int i = 0;
                for (ext_info = chan->ext_info; ext_info->name; ext_info++) {

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 2e45b3ceafa7c8e7492d31d890dcbf2cf64946f6..9a3cf481514851cccbbec343642a864383f2b012 100644 (file)
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -362,6 +362,8 @@ struct iio_trigger; /* forward declaration */
  *                     and max. For lists, all possible values are enumerated.
  * @write_raw:         function to write a value to the device.
  *                     Parameters are the same as for read_raw.
+ * @read_label:                function to request label name for a specified label,
+ *                     for better channel identification.
  * @write_raw_get_fmt: callback function to query the expected
  *                     format/precision. If not set by the driver, write_raw
  *                     returns IIO_VAL_INT_PLUS_MICRO.
@@ -420,6 +422,10 @@ struct iio_info {
                         int val2,
                         long mask);
 
+       int (*read_label)(struct iio_dev *indio_dev,
+                        struct iio_chan_spec const *chan,
+                        char *label);
+
        int (*write_raw_get_fmt)(struct iio_dev *indio_dev,
                         struct iio_chan_spec const *chan,
                         long mask);