missing iio_channel_get_label(const struct iio_channel *chn) function

[rgetz]

While libiio supports reading device labels for the last three years.

Some devices (ion hwmon) have channel labels - which seems to be a good idea for userspace:

        hwmon18: max15301 (label: VCCPSINT)
                5 channels found:
                        curr1:  (input)
                        4 channel-specific attributes found:
                                attr  0: crit (curr1_crit) value: 11015
                                attr  1: crit_alarm (curr1_crit_alarm) value: 0
                                attr  2: input (curr1_input) value: 1560
                                attr  3: label (curr1_label) value: iout1
                        temp2:  (input)
                        3 channel-specific attributes found:
                                attr  0: crit (temp2_crit) value: 115000
                                attr  1: crit_alarm (temp2_crit_alarm) value: 0
                                attr  2: input (temp2_input) value: 44375
                        in1:  (input)
                        3 channel-specific attributes found:
                                attr  0: alarm (in1_alarm) value: 0
                                attr  1: input (in1_input) value: 12000
                                attr  2: label (in1_label) value: vin
                        temp1:  (input)
                        3 channel-specific attributes found:
                                attr  0: crit (temp1_crit) value: 115000
                                attr  1: crit_alarm (temp1_crit_alarm) value: 0
                                attr  2: input (temp1_input) value: 41375
                        in2:  (input)
                        3 channel-specific attributes found:
                                attr  0: alarm (in2_alarm) value: 0
                                attr  1: input (in2_input) value: 849
                                attr  2: label (in2_label) value: vout1
                No trigger on this device

vin and vout1 is much more user intuitive than in1 and in2.

Supporting this with a function like:

   iio_channel_get_label(const struct iio_channel *chn)

seems like a no brainer...

See hwmon sysfs Doc:

in[0-*]_label	Suggested voltage channel label.
		Text string
		Should only be created if the driver has hints about what
		this voltage channel is being used for, and user-space
		doesn't. In all other cases, the label is provided by
		user-space.
		RO

fan[1-*]_label	Suggested fan channel label.
		Text string
		Should only be created if the driver has hints about what
		this fan channel is being used for, and user-space doesn't.
		In all other cases, the label is provided by user-space.
		RO

temp[1-*]_label	Suggested temperature channel label.
		Text string
		Should only be created if the driver has hints about what
		this temperature channel is being used for, and user-space
		doesn't. In all other cases, the label is provided by
		user-space.
		RO

IIO seems to support it as well:

What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_label
What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_label
KernelVersion:	5.8
Contact:	[email protected]
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_anglY_label
KernelVersion:	5.12
Contact:	[email protected]
Description:
		Optional symbolic label for channel Y.
		For Intel hid hinge sensor, the label values are:
		hinge, keyboard, screen. It means the three channels
		each correspond respectively to hinge angle, keyboard angle,
		and screen angle.

What:		/sys/bus/iio/devices/iio:deviceX/events/in_altvoltageY_mag_either_label
What:		/sys/bus/iio/devices/iio:deviceX/events/in_altvoltageY_mag_rising_label
What:		/sys/bus/iio/devices/iio:deviceX/events/in_altvoltageY_thresh_falling_label
What:		/sys/bus/iio/devices/iio:deviceX/events/in_altvoltageY_thresh_rising_label
What:		/sys/bus/iio/devices/iio:deviceX/events/in_anglvelY_mag_rising_label
What:		/sys/bus/iio/devices/iio:deviceX/events/in_anglY_thresh_rising_label
What:		/sys/bus/iio/devices/iio:deviceX/events/in_phaseY_mag_rising_label
KernelVersion:	6.7
Contact:	[email protected]
Description:
		Optional symbolic label to a device channel event.
		If a label is defined for this event add that to the event
		specific attributes. This is useful for userspace to be able to
		better identify an individual event.

its just libiio that does not.

[rgetz]

Here are the sequnce of commits that @pcercuei did for adding device labels - channel labels should be similar:

• Add API function iio_device_get_label()
• Enhance iio_context_find_device() to use labels We should enhance iio_device_find_channel() in this case.
• local: Init device label when found
• xml: Init device label when found

and then bindings:

• C#: Add support for reading device labels
• Python: Add support for reading device labels
• C++ wasn't supported so that will need to be done as well.

and then utils:

• iio_info: Display device label if present
• iio_attr: Display device label if present

and then (as a best practice) make sure that new kernel device drivers have labels if the channels will be mostly constant.

[nunojsa]

Agreed, makes sense to support this...

[rgetz]

would be nice to support this before 1.0 is released ...

??

[mhennerich]

Dan can you please have a look?

[dNechita]

Yes, I will make this a priority.