On Thu, Aug 21, 2008 at 10:10:33AM +1000, Neil Brown wrote: > On Monday August 18, dmitry.torokhov@xxxxxxxxx wrote: > > On Mon, Aug 18, 2008 at 10:51:33AM +1000, Neil Brown wrote: > > > But the X server still needs to know a little bit about /dev/tty to > > > make sure that control-C doesn't get delivered the wrong way. That's > > > awkward. > > > > Does it need to do anything besides switching VC into the raw mode? > > Probably not, no. > > > > > > It also negates much of the power of the input layer (easy hot-plug). > > > I don't much like that approach. > > > > > > > I think this is the only sensible approach though. X needs to have > > native hotplug capabilities anyway because of all these new mice that > > have bazillion of buttons on them that PS/2 emulation simply can not > > support. And once you have hotplug support in X and don't rely on > > myultiplexors anymore you can remove bunch of things, like grabbing > > devices in one fashion or another and you can even keep the devices > > open while switching to the text mode - no need to close and reopen > > them all the time. > > So your position is that for anything non-trivial, the clever stuff in > the input layer like multiplexing and simulating PS2 mice is not > sufficiently powerful and not worth fixing, and it should all be left > to userspace. Correct? Yes, due to limitations of the PS/2 protocol itself among other things. I am sure Vojtech will correct me but I believe he made /dev/input/mice as a stop-gap measure until X is ready... well, it was 8 some years ago ;( > I must confess a certain sympathy for that position, but it does make > solving my current problem harder - which dampens my enthusiasm :-) > Yeah, I can understand that. > So: The X server need to support hotplug of input devices. > Apparently there is code out there (for nearly 2 years) but it doesn't > seem to be in a release yet. > Quoting http://wiki.x.org/wiki/XInputHotplug > > The X.org server supports hotplugging input devices since November > 2006 > http://lists.freedesktop.org/archives/xorg/2006-October/019007.html > (X11R7.2 will NOT have hotplug support yet). > > So both the kernel and the X server could provide the hotplug support > required, but neither are really quite usable at the moment for very > different reasons. Sad. > Options... > First: problem description. > Device with a touchscreen wants: > - touch screen events to be delivered as absolute events to X > server. > - Other programs to be able to monitor the touch screen to > e.g. detect activity independently of whether an X server is in > use or direct fbdev access is happening (e.g. Qtopia). > - hot-plugged mice (e.g. bluetooth) should be recognised by > X server. > > We could: > 1/ Wait for X11 XInputHotplug to be released. > 2/ Hack a little input driver for X which somehow finds > mouse devices and interprets them. > 3/ Use kernel's input multiplexing and: > 3a/ change EVIOCGRAB to not exclude other evdev devices > 3b/ change EVIOCGRAB to optionally not exclude other evdev devices. > 3c/ somehow convince mousedev never to listen on the touchscreen. > > Did I miss anything? > > 3a is what the openmoko kernel (and presumably others) do today. But > it breaks backwards compatibility . > 3b is what I suggested but you don't like. > 1 does not provide a solution in a reasonable time frame > 2 is likely to be very messy and error prone > > So I'm now wondering about 3c. All these solutions require changes to userspace/drivers. I feel that this time is better spent on the X itself rather on various drivers re-implementing the same thing and stumbling over the same problems. > While I can understand the value of pretending that a touch-pad looks > like a mouse, a touch-screen is a very different thing. I don't > think it would ever make sense for a touch screen to generate > relative events. It probaibly was a mistake to make touchscreens go through /dev/input/mice. Again, the adea was to allow limitied use until proper driver is installed. > So how might we make our touchscreen appear uninteresting to > mousedev? > > We could get it to return some other 'key' rather one of > BTN_TOUCH BTN_TOOL_FINGER BTN_LEFT > > Maybe BTN_STYLUS. Given that the touchpad is designed for finger > usage it is a bit of a lie. But it would work. > > This is really sidestepping the issue. We really want to be able to > say "This is a device where relative events are completely > meaningless". I suspect that isn't going to happen though. > > tslib doesn't seem to care much about what key is sent. It only > looks for BTN_TOUCH, but all it sees is when the value goes to zero > as a "finger is removed" event. It equally gets that from > ABS_PRESSURE going to zero. > > So if I just arranged for the touchscreen to deliver BTN_STYLUS > instead of BTN_TOUCH it would hide it from all the mousedev devices > (which I think is the correct thing) and mean that the Xserver > doesn't need to use EVIOCGRAB, so we don't need to break it in the > kernel. > > OK, I think I can go forward with that. Thanks for listening. > Maybe openmoko could just patch mousedev to ignore touchscreens for now, until X is fixed? -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
