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SubjectRe: [PATCH v3 2/2] PM / Runtime: Add pm_runtime_enable_recursive
On 19 May 2015 at 19:49, Alan Stern <> wrote:
> On Tue, 19 May 2015, Tomeu Vizoso wrote:
>> This function makes less cumbersome to enable runtime PM in a device and
>> its descendants.
>> Signed-off-by: Tomeu Vizoso <>
> I don't see the point of this. In the scenario you have in mind, are
> the device and all its descendants registered by the same
> subsystem/driver?

Not quite, the scenario here is a driver (uvcvideo) that deals with a
specific piece of hardware and knows that all the descendants of the
device it's bound to are virtual.

The subtree is:

1-1:1.0 (bound to uvcvideo)

I liked how the force_direct_complete flag played out here, but I
agree with Rafael that it can be abused as the PM domain or the bus
type weren't able to prevent going directly to complete.

This is my testing branch, btw:

> If they are, can't the subsystem/driver code enable
> runtime PM for each of them when they are registered, by adding a
> single call in the right spot?
> If they don't all belong to the same subsystem/driver, who is going to
> call your pm_runtime_enable_recursive routine? No single caller will
> have the right to enable runtime PM for all these devices.

Yeah, I was thinking that uvcvideo might be able to decide that, but
I'm not really sure about it.



> Alan Stern
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