[PATCH v6 1/4] iio: core: Add optional symbolic label to a device channel

[PATCH v6 1/4] iio: core: Add optional symbolic label to a device channel

[Cristian Pop]

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>
---
Changes in V6:
 - Fix indentation
 - Check for "read_label callback" inside "iio_device_add_channel_label"
 
 drivers/iio/industrialio-core.c | 40 +++++++++++++++++++++++++++++++++
 include/linux/iio/iio.h         |  6 +++++
 2 files changed, 46 insertions(+)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 6e388293c828..b577fff35641 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -669,6 +669,19 @@ 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)
@@ -1137,6 +1150,28 @@ int __iio_add_chan_devattr(const char *postfix,
 	return ret;
 }
 
+static int iio_device_add_channel_label(struct iio_dev *indio_dev,
+					 struct iio_chan_spec const *chan)
+{
+	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,
+				     &indio_dev->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,
@@ -1270,6 +1305,11 @@ 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 2e45b3ceafa7..9a3cf4815148 100644
--- 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);
-- 
2.17.1

[PATCH v6 2/4] iio:Documentation: Add documentation for label channel attribute

[Cristian Pop]

If a label is defined 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>
---
Changes in v6:
 - Fix documentation
 Documentation/ABI/testing/sysfs-bus-iio | 72 +++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index a9d51810a3ba..53c5156362af 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1715,6 +1715,78 @@ Description:
 
 		Raw counter device counters direction for channel Y.
 
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_powerY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_powerY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_accelY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_accelY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_angl_velY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_angl_velY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_magnY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_magnY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_lightY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_lightY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_intensityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_intensityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_proximityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_proximityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_tempY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_tempY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_incliY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_incliY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_rotY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_rotY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_anglY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_anglY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_timestampY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_timestampY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_capacitanceY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_capacitanceY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_altvoltageY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_cctY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_cctY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_pressureY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_pressureY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_humidityrelativeY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_humidityrelativeY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_activityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_activityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_stepsY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_stepsY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_energyY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_energyY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_distanceY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_distanceY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_velocityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_velocityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_concentrationY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_concentrationY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_resistanceY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_resistanceY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_phY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_phY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_uvindexY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_uvindexY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_electricalconductivityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_electricalconductivityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_countY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_indexY_label
+What:		/sys/bus/iio/devices/iio:deviceX/in_gravityY_label
+What:		/sys/bus/iio/devices/iio:deviceX/out_gravityY_label
+KernelVersion:	5.8
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Optional symbolic label to a device channel.
+		If a label is defined for this channel add that to the channel
+		specific attributes. This is useful for userspace to be able to
+		better identify an individual channel.
+
 What:		/sys/bus/iio/devices/iio:deviceX/in_phaseY_raw
 KernelVersion:	4.18
 Contact:	linux-iio@vger.kernel.org
-- 
2.17.1

[PATCH v6 3/4] iio: adc: ad7768-1: Add channel labels.

[Cristian Pop]

For better identification of the channels.

Signed-off-by: Cristian Pop <cristian.pop@analog.com>
---
Changes in v6:
 - Use static variable for labels
 drivers/iio/adc/ad7768-1.c | 41 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 0e93b0766eb4..5c0cbee03230 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -161,6 +161,7 @@ struct ad7768_state {
 	struct completion completion;
 	struct iio_trigger *trig;
 	struct gpio_desc *gpio_sync_in;
+	const char *labels[ARRAY_SIZE(ad7768_channels)];
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
@@ -407,6 +408,14 @@ static int ad7768_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static int ad7768_read_label(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan, char *label)
+{
+	struct ad7768_state *st = iio_priv(indio_dev);
+
+	return sprintf(label, "%s\n", st->labels[chan->channel]);
+}
+
 static struct attribute *ad7768_attributes[] = {
 	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
 	NULL
@@ -420,6 +429,7 @@ static const struct iio_info ad7768_info = {
 	.attrs = &ad7768_group,
 	.read_raw = &ad7768_read_raw,
 	.write_raw = &ad7768_write_raw,
+	.read_label = ad7768_read_label,
 	.debugfs_reg_access = &ad7768_reg_access,
 };
 
@@ -532,6 +542,33 @@ static void ad7768_clk_disable(void *data)
 	clk_disable_unprepare(st->mclk);
 }
 
+static int ad7768_set_channel_label(struct iio_dev *indio_dev,
+						int num_channels)
+{
+	struct ad7768_state *st = iio_priv(indio_dev);
+	struct device *device = indio_dev->dev.parent;
+	struct fwnode_handle *fwnode;
+	struct fwnode_handle *child;
+	const char *label;
+	int crt_ch = 0;
+
+	fwnode = dev_fwnode(device);
+	fwnode_for_each_child_node(fwnode, child) {
+		if (fwnode_property_read_u32(child, "reg", &crt_ch))
+			continue;
+
+		if (crt_ch >= num_channels)
+			continue;
+
+		if (fwnode_property_read_string(child, "label", &label))
+			continue;
+
+		st->labels[crt_ch] = label;
+	}
+
+	return 0;
+}
+
 static int ad7768_probe(struct spi_device *spi)
 {
 	struct ad7768_state *st;
@@ -604,6 +641,10 @@ static int ad7768_probe(struct spi_device *spi)
 
 	init_completion(&st->completion);
 
+	ret = ad7768_set_channel_label(indio_dev, ARRAY_SIZE(ad7768_channels));
+	if (ret)
+		return ret;
+
 	ret = devm_request_irq(&spi->dev, spi->irq,
 			       &ad7768_interrupt,
 			       IRQF_TRIGGER_RISING | IRQF_ONESHOT,
-- 
2.17.1

[PATCH v6 4/4] dt-bindings:iio:adc:adi,ad7768-1: Add documentation for channel label

[Cristian Pop]

Optional attribute for better identification of the channels.

Signed-off-by: Cristian Pop <cristian.pop@analog.com>
---
 .../bindings/iio/adc/adi,ad7768-1.yaml        | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
index d3733ad8785a..0c75ce73ffe9 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
@@ -29,6 +29,12 @@ properties:
   interrupts:
     maxItems: 1
 
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
   vref-supply:
     description:
       ADC reference voltage supply
@@ -61,6 +67,23 @@ required:
   - spi-cpha
   - adi,sync-in-gpios
 
+patternProperties:
+  "^channel@([0-9]|1[0-5])$":
+    type: object
+    description: |
+      Represents the external channels which are connected to the device.
+
+    properties:
+      reg:
+        description: |
+          The channel number.
+
+      label:
+        description: |
+          Unique name to identify which channel this is.
+    required:
+      - rega
+
 additionalProperties: false
 
 examples:
@@ -84,6 +107,14 @@ examples:
             reset-gpios = <&gpio 27 GPIO_ACTIVE_LOW>;
             clocks = <&ad7768_mclk>;
             clock-names = "mclk";
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 {
+                reg = <0>;
+                label = "channel_0";
+            };
         };
     };
 ...
-- 
2.17.1

Re: [PATCH v6 4/4] dt-bindings:iio:adc:adi,ad7768-1: Add documentation for channel label

[Jonathan Cameron]

On Mon, 21 Sep 2020 16:30:20 +0300
Cristian Pop <cristian.pop@analog.com> wrote:

Hi Cristian,

> Optional attribute for better identification of the channels.
Dt-bindings need to be sent to the dt-binding maintainer and
list.
+CC.

I'll definitely be looking for a review from Rob on this one as we are defining
a new generic binding.

@Rob, the only new bit in here is the label for an individual channel.
The rest has been defined for a while to allow us to control channel
specific aspects of an ADC.

We should also look to add it to the top level docs.

In this case, probably
Documentation/device-tree/bindings/iio/adc/adc.txt

Currently only ADCs have a channel description to add this to.
We can look at making this more generic if it turns out to make sense
for other types of IIO device.

Thanks,

Jonathan


> 
> Signed-off-by: Cristian Pop <cristian.pop@analog.com>
> ---
>  .../bindings/iio/adc/adi,ad7768-1.yaml        | 31 +++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> index d3733ad8785a..0c75ce73ffe9 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> @@ -29,6 +29,12 @@ properties:
>    interrupts:
>      maxItems: 1
>  
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
>    vref-supply:
>      description:
>        ADC reference voltage supply
> @@ -61,6 +67,23 @@ required:
>    - spi-cpha
>    - adi,sync-in-gpios
>  
> +patternProperties:
> +  "^channel@([0-9]|1[0-5])$":
> +    type: object
> +    description: |
> +      Represents the external channels which are connected to the device.
> +
> +    properties:
> +      reg:
> +        description: |
> +          The channel number.
> +
> +      label:
> +        description: |
> +          Unique name to identify which channel this is.
> +    required:
> +      - rega
rega?  Also, one I learnt the other day.  Need to have

       additionalProperties: false

for child nodes as well as the base node.

> +
>  additionalProperties: false
>  
>  examples:
> @@ -84,6 +107,14 @@ examples:
>              reset-gpios = <&gpio 27 GPIO_ACTIVE_LOW>;
>              clocks = <&ad7768_mclk>;
>              clock-names = "mclk";
> +
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            channel@0 {
> +                reg = <0>;
> +                label = "channel_0";
> +            };
>          };
>      };
>  ...

Re: [PATCH v6 2/4] iio:Documentation: Add documentation for label channel attribute

[Jonathan Cameron]

On Mon, 21 Sep 2020 16:30:18 +0300
Cristian Pop <cristian.pop@analog.com> wrote:

> If a label is defined 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>
> ---
> Changes in v6:
>  - Fix documentation
>  Documentation/ABI/testing/sysfs-bus-iio | 72 +++++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index a9d51810a3ba..53c5156362af 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -1715,6 +1715,78 @@ Description:
>  
>  		Raw counter device counters direction for channel Y.
>  
> +What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_label

Please limit this to those channels for which we are implementing it
in this patch set.  Others should be added if/as we use them.

For some channel types I'm not sure it will ever be used.  It doesn't necessarily
make sense to define a label for the xaxis of an accelerometer for example.

Thanks,

Jonathan

> +What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_powerY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_powerY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_accelY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_accelY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_angl_velY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_angl_velY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_magnY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_magnY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_lightY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_lightY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_intensityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_intensityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_proximityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_proximityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_tempY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_tempY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_incliY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_incliY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_rotY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_rotY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_anglY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_anglY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_timestampY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_timestampY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_capacitanceY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_capacitanceY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_altvoltageY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_cctY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_cctY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_pressureY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_pressureY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_humidityrelativeY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_humidityrelativeY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_activityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_activityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_stepsY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_stepsY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_energyY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_energyY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_distanceY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_distanceY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_velocityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_velocityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_concentrationY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_concentrationY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_resistanceY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_resistanceY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_phY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_phY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_uvindexY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_uvindexY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_electricalconductivityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_electricalconductivityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_countY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_countY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_indexY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/in_gravityY_label
> +What:		/sys/bus/iio/devices/iio:deviceX/out_gravityY_label
> +KernelVersion:	5.8
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Optional symbolic label to a device channel.
> +		If a label is defined for this channel add that to the channel
> +		specific attributes. This is useful for userspace to be able to
> +		better identify an individual channel.
> +
>  What:		/sys/bus/iio/devices/iio:deviceX/in_phaseY_raw
>  KernelVersion:	4.18
>  Contact:	linux-iio@vger.kernel.org

Re: [PATCH v6 1/4] iio: core: Add optional symbolic label to a device channel

[Jonathan Cameron]

On Mon, 21 Sep 2020 16:30:17 +0300
Cristian Pop <cristian.pop@analog.com> wrote:

> 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>
Hi Cristian,

Looks good to me as does patch 3.  Just the docs and DT to tidy up now.

Thanks,

Jonathan

> ---
> Changes in V6:
>  - Fix indentation
>  - Check for "read_label callback" inside "iio_device_add_channel_label"
>  
>  drivers/iio/industrialio-core.c | 40 +++++++++++++++++++++++++++++++++
>  include/linux/iio/iio.h         |  6 +++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 6e388293c828..b577fff35641 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -669,6 +669,19 @@ 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)
> @@ -1137,6 +1150,28 @@ int __iio_add_chan_devattr(const char *postfix,
>  	return ret;
>  }
>  
> +static int iio_device_add_channel_label(struct iio_dev *indio_dev,
> +					 struct iio_chan_spec const *chan)
> +{
> +	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,
> +				     &indio_dev->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,
> @@ -1270,6 +1305,11 @@ 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 2e45b3ceafa7..9a3cf4815148 100644
> --- 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);