On Tue, 8 Jan 2013, Lan Tianyu wrote:
> On 2013年01月08日 02:44, Alan Stern wrote:
> > On Sun, 6 Jan 2013, 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.
> >
> >> @@ -165,8 +166,12 @@ int usb_hub_create_port_device(struct usb_hub *hub, int port1)
> >> if (retval)
> >> goto error_register;
> >>
> >> - pm_runtime_set_active(&port_dev->dev);
> >> - pm_runtime_enable(&port_dev->dev);
> >> + if (!dev_pm_qos_expose_flags(&port_dev->dev,
> >> + PM_QOS_FLAG_NO_POWER_OFF)) {
> >> + pm_runtime_set_active(&port_dev->dev);
> >> + pm_runtime_enable(&port_dev->dev);
> >> + }
> >
> > I don't understand this. Why does this code need to be conditional?
> >
> If expose pm qos flag failed, user space couldn't prevent device from
> being powered off. This will be dangerous. So for safety, disable port's
> runtime pm if it failed.
Then the pm_runtime_enable call should be conditional, but the
pm_runtime_set_active call should not be. You also might add a comment
explaining this.
Alan Stern
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