On Fri, 9 Sep 2005, Robert Marquardt wrote: > Alan Stern wrote: > > > That doesn't sound like a very good strategy in general. Configurations > > don't have to be listed in any particular order; why should the first one > > be treated specially? > > There are only two ways possible for preferencing a configuration.
"Preferencing"? Do you mean "indicating which configuration should be preferred"? Or do you mean "choosing which configuration to prefer"? > Ordering of the configurations or the configuration number in the > configuration itself. That number is commonly not used for expressing a > preference. How do you know what is or is not commonly done? Have you made a survey? > > How do you know what strategy Windows uses? > > Simply by testing with a clean device which presents a high power > configuration followed by a low power configuration. > The idea is to have a device being able to draw the max power available > for charging purposes. It should allow the numerous idiots currently > simply drawing power from the USB without a device to build a valid > charger device. > The correct handling of such a device on a low power port should either > be to choose the low power configuration or not to configure the device. > In that situation the device disconnects and reconnects with the > configurations swapped. You made a long speech here, but you didn't answer my question. How do you know which strategy Windows uses? Did somebody at Microsoft tell you? > Currently MacOS 9 correctly chooses the low power configuration. MaxOS X > does not configure the device and accepts it after the reconnect. > Windows XP switches off the port which prevents the reconnect. > Linux configures the device with the high power configuration. > Win XP only behaves badly. Linux is in blatant violation of the spec. > Now such a device may draw all of the 500 mA from a bus powered hub > already serving three other low power devices. A correctly implemented > hub will detect an overcurrent situation and switch off completely > dragging down (at least) three completely innocent devices. > > A bugfix of this is really needed for Linux. It is a violation of the spec. > A simple patch only fixing this by not configuring he device would be > best because it has the best chances to get accepted to the next kernel > release. Anything beyond that is disputable (after all we are currently > in dispute over it :). I keep getting the feeling that you don't read anything I send to you. The patch I pointed out to you contains exactly such a bugfix! Why haven't you tried using it? Alan Stern ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
