Re: [PATCH 9/9] PM / Domains: Add dev_pm_domain_attach_by_id() to manage multi PM domains

[Jon Hunter]

On 25/05/18 11:45, Ulf Hansson wrote:

...

> > Right, but this case still seems like an error. My understanding is that
> > only drivers will use this API directly and it will not be used by the
> > device driver core (unlike dev_pm_domain_attach), so if anyone calls this
> > attempting to attach another PM domain when one is already attached, they
> > are doing something wrong.
>
> [...]
>
> You may be right!
>
> What I was thinking of is whether multiple PM domains may be optional
> in some cases, but instead a PM domain have already been attached by
> dev_pm_domain_attach(), prior the driver starts to probe.
>
> Then, assuming we return an error for this case, that means the caller
> then need to check the dev->pm_domain pointer, prior calling
> dev_pm_domain_attach_by_id(). Wouldn't it? Perhaps that is more clear
> though?

IMO the driver should know whether is needs multiple power-domains or 
not and if it needs multiple then it should just call 
dev_pm_domain_attach_by_id() N times without needing to checking 
dev->pm_domain first. If it fails then either the PM domain core did 
something wrong or power-domains are missing from DT, but either way 
there is an error, so let it fail.

Cheers
Jon

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nvpublic