Messages in this thread | | | Date | Tue, 22 Feb 2022 09:42:12 +0200 | Subject | Re: [RFC PATCH] iio: core: provide a default value `label` property | From | Nandor Han <> |
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On 2/20/22 15:18, Jonathan Cameron wrote: > On Wed, 16 Feb 2022 15:56:04 +0200 > Nandor Han <nandor.han@vaisala.com> wrote: >
Thanks for reviewing the patch and provide feed back.
>> The label property is used to correctly identify the same IIO device >> over reboots. The implementation requires that a value will be provided >> through device-tree. This sometime could requires many changes to >> device-trees when multiple devices want to use the label property. >> In order to prevent this, we could use the device-tree node >> name as default value. The device-tree node name is unique and >> also reflects the device which makes it a good choice as default value. >> This change is backward compatible since doesn't affect the users that >> do configure a label using the device-tree or the ones that are not >> using the labels at all. >> >> Use the device-tree node name as a default value for `label` property, >> in case there isn't one configured through device-tree. > > Interesting idea. However a few concerns come to mind. > 1) If we start having a default for this, then it will get used as ABI > and if a label is applied later to the DT then we will end up breaking > userspace scripts.
When a label is explicitly configured means that the userspace expects to have that value available. Therefore, I don't see this as ABI change, given that this affects the property label content and not for example the property name.
> 2) If we do this it should be firmware agnostics (we need to fix > the existing code to be such as well).
Not sure I understand this. If you could explain a bit more I would really appriciate.
> 3) Is the node name always unique (think multiple accelerometers on > different i2c masters)? > 3) I'm fairly sure this information is readily available anyway. > either via the of_node link for the iio\:deviceX > So why not have your usespace use that instead of label? > I'm not a fan of duplicating information that is readily available > anyway - be it as name and reg in the of_node directory. >
The node name supposed to be unique AFAIK and you're right it is available already in the userspace. My point with this patch is to provide a default value for the label content and I'm open to suggestions related to content. The of_node name was something that I thought that is unique and easy to use, but if somebody has better suggestions I'm really open to these.
> Thanks, > > Jonathan >
<snip>
Thanks again and regards, Nandor
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