Re: Do we need asynchronous pm_runtime_get()? (was: Re: bisected regression ...)

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On Mon, 6 Aug 2012, Ming Lei wrote:

> Maybe the return value should be passed to caller. Also the race between
> 'func' and its .runtime_resume callback should be stated in comment.
> 
> In fact, maybe it is better to call 'func' always first, then call
> ' rpm_resume(dev, RPM_ASYNC);', otherwise the driver may
> be confused about the order between 'func' and its .runtime_resume
> callback.

> Another way is to define 'func' as 'runtime_pre_resume'
> in 'struct dev_pm_ops', and there are some advantages about this way:
> 
>         - save one pointer in 'struct devices, since most of devices
> don't need the 'func'
>         - well documents on 'runtime_pre_resume'
>         - caller of pm_runtime_get_and_call may be happier, maybe just
>         pm_runtime_get or *_aync is enough.

No, no, you have completely misunderstood the whole point of this 
change.

The idea is for "func" to be called at a time when it is known that the 
device is at full power.  That means it _has_ to be called after the 
runtime_resume callback returns.

Also, "func" should not be stored in dev_pm_ops because it won't be a 
read-only value.

Alan Stern

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