linux-kernel - Re: [PATCH v2 7/7] USB / PM: Allow USB devices to remain runtime-suspended when sleeping

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Date:	Fri, 03 Apr 2015 23:23:32 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	linux-pm@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Scot Doyle <lkml14@...tdoyle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Dan Williams <dan.j.williams@...el.com>,
	Julius Werner <jwerner@...omium.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Pratyush Anand <pratyush.anand@...com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] USB / PM: Allow USB devices to remain runtime-suspended when sleeping

On Friday, April 03, 2015 01:44:36 PM Dmitry Torokhov wrote:
> Hi Tomeu,
> 
> On Fri, Apr 03, 2015 at 02:57:56PM +0200, Tomeu Vizoso wrote:
> > Have dev_pm_ops.prepare return 1 for USB devices, interfaces, endpoints
> > and ports so that USB devices can remain runtime-suspended when the
> > system goes to a sleep state, if their wakeup state is correct.
> > 
> > Also enable runtime PM for endpoints, which is another requirement for
> > the above to work.
> 
> After patching I think the 4th unrelated subsystem with stubs for
> prepare() I think it is pretty clear that this approach is not the right
> one.
> 
> If your driver does not care about any children hanging off it there is
> dev->ignore_children flag that either already does what you want, or
> maybe needs adjusted to support your use case.

I wouldn't overload ignore_children with that meaning.  That said adding
a "return 1 from device_prepare() if this is set" flag might be a good idea.


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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