On Thu, 8 May 2014, Dan Williams wrote: > > I don't understand this last part. Why do we need to guarantee the > > child device has recovered from power loss? Why not proceed the same > > way we do now when the child is suspended? > > Two reasons I believe: > > 1/ The child may be gone, and usb_port_resume() will mark it for disconnect > > 2/ Currently port_event() knows how to handle suspended devices > (USB_PORT_STAT_C_SUSPEND), but in the case of power loss recovery the > status and change bits are different. I figure why special case > port_event()? Just make it so it handles all the same cases that are > presented when the port does not lose power.
How much special casing would really be needed? > > If you take that stuff out, it seems that there won't be any need to > > use wakeup_bits or usb_kick_khubd() for this purpose. > > See 1/ I think we want to handle disconnects right away, hence the khubd kick. If the child has been disconnected, pm_request_resume()'s callback will determine that fact quickly enough. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
