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

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.



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