On Thu, 27 Sep 2012, Ming Lei wrote: > This patch sets hub device's default autosuspend delay as 0 to > speedup bus suspend, see comments in code for details. > > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > --- a/drivers/usb/core/hub.c > +++ b/drivers/usb/core/hub.c > @@ -1629,6 +1629,40 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id) > desc = intf->cur_altsetting; > hdev = interface_to_usbdev(intf); > > + /* > + * Set default autosuspend delay as 0 to speedup bus suspend, > + * based on the below considerations: > + * > + * - Unlike other drivers, the hub driver does not rely on the > + * autosuspend delay to provide enough time to handle a wakeup > + * event, and the submitted status URB is just to check future > + * change on hub downstream ports, so it is safe to do it. > + * > + * - The patch might cause one or more auto supend/resume for > + * below very rare devices when they are plugged into hub > + * first time: > + * > + * devices having trouble initializing, and disconnect > + * themselves from the bus and then reconnect a second > + * or so later > + * > + * devices just for downloading firmware, and disconnects > + * themselves after completing it > + * > + * These quite rare devices still can change the autosuspend > + * delay of their parent hub in the probe() to one appropriate > + * value to avoid the subtle problem if someone does care it. It's not a good idea for some random USB driver to start changing the parent hub's autosuspend delay. In fact, it's not a good idea for _any_ driver to start changing settings for devices it doesn't own. 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
