Re: [PATCH v2 2/2] iio: adc: ti-ads1015: Add support for label

[Flaviu Nistor <flaviu.nistor@gmail.com>]

On Thu, Sep 3, 2026 at 9:18 AM, Andy Shevchenko wrote:
>On Wed, Sep 02, 2026 at 01:37:45PM -0500, David Lechner wrote:
>> On 9/2/26 12:22 PM, Flaviu Nistor wrote:
>
>...
>
>> > +		if (fwnode_property_present(node, "label")) {
>> > +			ret = fwnode_property_read_string(node, "label", &label);
>> > +			if (ret) {
>> > +				dev_err(dev, "invalid label on %pfw\n", node);
>> > +				return ret;
>
>				return dev_err_probe(...);
>
>> > +			}
>> > +			data->channel_data[channel].label = label;
>> > +		} else {
>> > +			data->channel_data[channel].label = "";
>> 
>> I think the normal way to do this is to return -EINVAL on channels with no
>> label rather than an empty string.
>
>
>In this case the whole dance with property_present is not required.
>(What you are saying sounds like label is mandatory property, but
> how the old DT will work that have no such property?)
>

I also consider that since label is not a mandatory property it should
not return -EINVAL just be simply not being used in the device tree for
that channel. Since the iio core exposes in sysfs the in_volatagex_label
for all channels, there are 3 situations:
1. The channel is defined in the dts and has the optional label property
assigned, in which case a string is returned in the console in user space.
2. The channel is defined in the dts but has no optional label property
defined in the dts, in which case it an empty string "" (a default) is
returned.
3. The channel is not defined in the dts (in_voltagex_label is still visible
in the sysfs), and reading the label will cause "(null)\n" to be printed in
the console (as indicated also by Sashiko boot), since the default "" value
is not assigned during device_for_each_child_node_scoped(). I think this is
not an issue since is just the way sysfs_emit() handles an NULL string.

My initial version (v1) handeled all 3 cases, for case 2 and 3, an empty string
"" was printed out.

What would you prefer? Any further suggestions?

Best regards,
Flaviu Nistor

>> > +		}
>
>-- 
>With Best Regards,
>Andy Shevchenko