Hi, On Tue, Jul 26, 2011 at 4:42 PM, Oliver Neukum <oneukum@xxxxxxx> wrote: > Am Dienstag, 26. Juli 2011, 10:17:59 schrieb Ming Lei: >> > This precise instruction is a fairly clear indication that the >> > rhdev->bus_mA value is a per-port limit and not a global hub limit. >> > Otherwise, there wouldn't have been this maximum value of 500mA. >> >> I understand 500mA is shared by all bus-powered devices attached to >> the port of root hub, so rhdev->bus_mA should be used as global value. >> And for each individual port of root hub, the max power is 500mA. > > Some very small battery powered devices (IIRC it was reported for a > device called Spitz by Pavel Machek) cannot supply the full 500mA. > Hence we have code to deal with this special situation. Currently hcd->power_budget is used for such purpose, for example, the max power provided by otg controller is 100mA. But what Thomas is wanting is that the max power provided by individual port in root hub can be customized, which is not supported by current kernel, but looks like not difficult to do it. thanks, -- Ming Lei -- 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
