Android phone as computer mouse

Question

I created an Android app that serves the touch screen sensor data to a java client that is listening on Debian Lenny machine.

The client maps this data to locations on the screen just like a wacom pad does. I would like to out put the x_loc and y_loc to a file and have the file recognized as a device.(I foggily believe this is how it is supposed to work)

I have experience with Linux but have not had to create a device before. How do I tell Linux that this file is a mouse. Do I have to create a driver?

Answer 1

You can either write a linux device driver to interpret your data as a genuine mouse, or you can convince the X server (or whatever else) to accept input from something else, such as a named pipe.

Actual device files are not files with any content - they are merely references to a major and minor number used to talk to a driver in the kernel which can perform vaguely file-like options on some device. You create device files with mknod, but they won't work until backed by a kernel driver with matching numbers. Believe there are now some stub mechanisms so the bulk of the actual driver can run in userspace.

Answer 2

There's many ways to do this, ranging from writing an actual device driver, over writing X clients to generate X events (using the XTest extension for example), to using kernel interfaces to inject input subsystem events.

I'd go with the last one and use the uinput subsystem. That's part of pretty much all recent kernels and provides /dev/uinput, which you can open regularly and do various ioctls on to create input devices from regular userspace.

Please also note that some mechanisms for this already exist. Bluetooth Human Interface Devices, which work just fine on Linux, are one example. rinputd, a daemon to listen to rinput clients and generating uinput events based on the data they send. is another. You might want to consider just making your Android app akt as an rinput client.