On Fri, 30 Nov 2012, Lan Tianyu wrote:

> On 2012年11月29日 01:44, Alan Stern wrote:
> > On Sat, 17 Nov 2012, Lan Tianyu wrote:
> > 
> >> This patch is to expose usb port's pm qos flags(pm_qos_no_power_off,
> >> pm_qos_remote_wakeup) to user space. User can set pm_qos_no_power_off
> >> flag to prohibit the port from being power off.
> > 
> > Do we really need this?  The user already can prevent the port from
> > being powered off by writing "on" to the power/control attribute.
> > 
> Hi Alan:
>       First, I think your suggestion could work. But I still have some 
> concerns.
>       (1) power/control is to control runtime pm rather than power off, this
> maybe confuse user space to use it to prevent power off. PM qos would be
> more generic and friendly since it is dedicated to power off control.

Well, power-off is a form of power management, so preventing power-off 
by preventing runtime PM makes sense.

>       (2) Some other buses(e.g SATA, PCI and etc) would also use PM qos to
> control power off, too. So, I think we should keep consistency to be
> convenient for user space to control. Keep using one same attribute to
> control all kinds of devices.

This second point is a very good one.  You should include it in the 
patch description.

Alan Stern

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