On Sun, 11 Nov 2012, Lan Tianyu wrote: > On 2012/11/10 0:10, Alan Stern wrote: > > On Fri, 9 Nov 2012, Lan Tianyu wrote: > > > >> Some usb devices can't be resumed correctly after power off. This > >> patch is to add pm qos flags request to change NO_POWER_OFF and > >> provide usb_device_allow_power_off() for device drivers to allow or > >> prohibit usb core to power off the device. > > > > If the reason for adding this request is to prevent the device from > > being powered off, then shouldn't the PM QOS flag be associated with > > device rather than with the port? > Hi Alan: > Great thanks for your review and good suggestions. > For pm qos flags, If put it on the port device, there is an advantage > that it can cover port without device or unused port and this part > didn't present in my this patchset. Right. That's a big advantage. > > In fact, it seems reasonable to have such a flag for both the device > > and the port. > You mean for usb device or usb interface device? USB device. > I think port and device are bound. Power off port also means to power > off device. So prevent device from power off also means to prevent port > from power off. They just like a power domain. Because power is on the > port and so I thought we just needed to have pm qos flag on the port. Consider what happens when the device is unplugged. The restriction against powering off the device won't be needed any more, but the PM QOS flag will still be set for the port. > This maybe a simple version. If necessary, I also could add pm qos flag > for usb or usb interface device later. Okay. Alan Stern -- 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
