On 2013年01月08日 23:16, Alan Stern wrote:
> 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.
Ok. I get it and will update soon.
>
> Alan Stern
>
--
Best regards
Tianyu Lan
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