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.
> Alan Stern
>
--
Best regards
Tianyu Lan
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