On Fri, May 3, 2013 at 6:29 AM, Simon Farnsworth <simon.farnsworth@xxxxxxxxxx> wrote: > Could you consider a gamepad equivalent of libv4l2 (source found in > http://git.linuxtv.org/v4l-utils.git/tree/HEAD:/lib )? [8<] > A gamepad version would intercept opens of /dev/input/event* nodes, and if > that node was a gamepad, do the remapping from gamepad-specific events to the > standard gamepad events. You can then use this with unmodified apps as an > LD_PRELOAD, or with modified apps as a shared library that only gets in the way > if the app is accessing a gamepad. The problem here is that this really shouldn't be a shared library if it's going to be accessed directly by (say) games. Unless there's something I'm missing, accessing /dev/input/event* requires elevated privileges, and the idea that all games will run as root kind of terrifies me. The only way it makes sense is either: - as a library for the X11 or Wayland server, in which case it might a well be a static library - as a server delivering events over AF_UNIX or AF_INET sockets If non-root clients are going to want to talk to this, it needs to be mediated by something. Unless there's some ELF trickery I don't know about, that means passing through some sort of RPC mechanism, whether it's X11, Wayland or the network stack. I suppose there's d-bus, but I'm reluctant to involve xml parsing in anything with performance requirements. I've got a prototype server now, actually; it isn't binding an address yet, but it should be shortly. It basically throws an inotify watch on /dev/input and maintains a list of active devices that it understands, with open file descriptors. The next stage is to get it binding a port on localhost and dumping appropriately rewritten events via udp. It'd be nice to use SOCK_SEQPACKET, but does anyone other than me actually build their kernel with sctp support? The way I'm currently planning this is essentially in two parts; a static library that deals with slurping and massaging data from evdev, and a server built with it that spews the results out in a udp torrent to whoever is listening. The hope would be that your graphical library of choice (X11, Wayland...) builds against the static lib and delivers the messages through its own standardized RPC mechanism. In the mean time, the server is there partly as a testbed and partly so that you don't have to run your game as root to get a gamepad. Todd. -- Todd Showalter, President, Electron Jump Games, Inc. -- 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
