Re: [PATCH v1 1/1] device property: Document how to check for the property presence

[Sakari Ailus]

Hi Andy,

On Wed, Mar 18, 2026 at 10:03:27AM +0200, Andy Shevchenko wrote:
> On Wed, Mar 18, 2026 at 12:27:24AM +0200, Sakari Ailus wrote:
> > On Tue, Mar 17, 2026 at 10:08:28PM +0100, Andy Shevchenko wrote:
> 
> ...
> 
> > > + * In order to check for the property presence, use device_property_present().
> > 
> > Do you really think we should add this clause for each of these functions?
> 
> Yes, as Guenter pointed out that this has to be documented clearly.
> 
> > I don't think it belongs here.
> 
> And? What should we do then (taking into account my below comments)?
> 
> > The error code list doesn't document what is returned if a property doesn't
> > exist (-EINVAL) and it'd be helpful to add this.
> 
> No, this change is exactly against this. Because using an error code that may
> cover not only that case is at bare minimum fragile and layering violation.
> APIs that require to know the implementation details are not good APIs.

I have to say I disagree with that, there's nothing wrong with checking
error codes if you need to.

Either way, I checked the original patch. If you really think you need to
check for property presence and use default in the case the property isn't
found and error out on other errors, add helper functions for the purpose
instead of open-coding it all.

> 
> > It would have been best to have a separate error code for this albeit
> > changing this now might not be that troublesome either: very, very few
> > callers depend on receiving such an error code but there are still many
> > callers.
> 
> I'm against this because we have already a dedicated API to check for property
> presence, why do we need to have another (confusing!) way of doing the same?
> 
> Having a dedicated code may help to debug, but shouldn't be used as a main
> feature in my opinion.

-- 
Regards,

Sakari Ailus