>> But there is this comment in the usb_suspend function,
>>
>> /* If udev is already suspended, we can skip this suspend and
>> * we should also skip the upcoming system resume. High-speed
>> * root hubs are an exception; they need to resume whenever the
>> * system wakes up in order for USB-PERSIST port handover to work
>> * properly.
>> */
>> if (udev->state == USB_STATE_SUSPENDED) {
>> if (udev->parent || udev->speed != USB_SPEED_HIGH)
>> udev->skip_sys_resume = 1;
>> return 0;
>> }
>>
>>
>> My question is, if the host is connnecting to a high speed device,
>> what would be the impact to remove the condition "udev->speed !=
>> USB_SPEED_HIGH" in this function?
>Removing that test would cause full-speed root hubs (i.e., USB-1.1 root
>hubs) to be resumed unnecessarily. This is true regardless of whether
the host is connected to a high-speed device.
I think I was confused by the logic :(, so for any non-high-speed udev,
skip_sys_resume would be set to 1, but for high speed udev,
skip_sys_resume would be set only if udev->parent is valid.
I'm still not sure how to interprete the comment "High-speed root hubs
are an exception; they need to resume whenever the system wakes up in
order for USB-PERSIST port handover to work properly". What is broken if
we set skip_sys_resume regardless of the speed?
Thanks,
Fei
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
