On Mon, Dec 17, 2001 at 12:02:06PM -0800, Greg KH wrote: > > That deferring may not always be possible. As an example, take a system > > in use by a friend of mine, basically a laptop with the keyboard not > > part of the main unit, but on the end of a USB lead that has to be > > disconnected to get it in its carrycase - and it has FOUR USB ports on > > the main case. As it happens, Simon uses it exclusively under Win2K, and > > that doesn't care what port the keyboard is plugged into on resume. If > > he chose to run it under Linux, would that care? > > Both Linux and Windows multiplex all keyboards together (USB and ps2), > so no, Linux does not care about where on the USB tree it exists.
But it will at some point in 2.5, because of multihead support. > > Remember, one of the basic design aims of USB was that the location a > > device is plugged in is irrelevant to the user. > > Heh, that might have been a nice goal at the beginning of the USB spec > process, but then reality hit :) That's a pretty exact description. > USB printer drivers on Windows for some manufacturers use the device > serial number to keep track of where the user plugged in a specific > printer, to keep that printer's settings correct. Lots of printers do > not have serial numbers, so those driver authors have to use the > topology. > > USB to serial drivers on Windows also do this same thing (mostly they > rely on the usb topology). > > And in talking with some of the core USB spec authors, they wish they > had mandated the serial number option to help alleviate some of the > problems that now happen. The problem with serial numbers is that you have to program every device's ROM you manufacture separately - no way to use non-programmable silicon mask ROMs, which are much cheaper in mass production. > Not true at all. If a driver knows where a device is, it can do more > things. Currently no Linux driver cares about topology, but that might > change in 2.5. The new HID drivers do care and pass that info to the input core. And it'll be very useful, namely for multihead and other fun stuff. -- Vojtech Pavlik SuSE Labs _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
