On Thu, Apr 01, 2010 at 11:23:16AM +0200, Jiri Kosina wrote: > On Thu, 1 Apr 2010, Attila Nagy wrote: > > > >>>> I've just found this thread: > > >>>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/492056 and the > > >>>> following patch: > > >>>> http://launchpadlibrarian.net/38497329/0001-HID-handle-joysticks-with-large-number-of-buttons.patch > > >>>> > > >>>> If I understand, this pushes the limit on the number of the buttons > > >>>> per joystick to 56? > > >>>> > > >>>> Shouldn't this limit be raised to some more? In fact if I understand > > >>>> the HID specification one could define 65K buttons per device. Well > > >>>> that's a bit silly, but I found this bug when I was about to build a > > >>>> hid device that has 64 buttons (or maybe more). > > >>>> > > >>>> I wonder if there's a possibility to push this limit a bit further? I > > >>>> guess 256 could be a reasonable limit for a while. > > >>> > > >>> Is this still a joystick though? Wouldn't it better to have those be KEY_* > > >>> events? > > >> > > >> Thanks for your reply. > > >> > > >> This is a bit philosophical question. In the practical side people > > >> like me choose to implement joystick hardware, because games have a > > >> decent support for joys with many buttons. If I have an interface, > > >> that has 64 buttons, I can map them in a game to functions as I want, > > >> without interferencing with the keyboard events. > > >> > > >> In the terms of the HID usage tables, one might should define these > > >> things as a game pad, or a "simulation control device", but support > > >> for such devices in current operating systems isn't that self > > >> understanding like support for a joystick. > > > I'll test it with 128 buttons today. > > > > I've tried 128 buttons. Currently the mapping space goes until 0x2ff, > > thus leaving room for 64 effective buttons per device. Over that only > > the lower 64 is reported and working, buttons over that are silently > > ignored. > > > > The attached patch raises this limit to 128 per device. Only two > > constants need to be modified, and after that everything did work fine > > for me. > > > > Could this hurt something, I didn't notice? > > > > > > [if I'm knocking on the wrong door, then please redirect me to the > > appropriate people] > > This should definitely go through Dmitry. Adding him, and linux-input@, to > CC. > I do not think it makes much sense - userspace has no way of knowing what actions these 'events' are supposed to signal (as opposed to BTN_THUMB, etc). These are purely programmable. So instead of inflating keymap tables, maybe such devices should just use ABS_MISC to transmit state and we may even think about teaching joydev to recognize it. -- 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
