USB Human Interface Device (HID) Configuration

General HID Configuration

There are two options for using a USB mouse or a USB keyboard - the standalone Boot Protocol (HIDBP) way and the full featured HID driver way. The Boot Protocol way is generally inferior, and this document describes the full featured way. The Boot Protocol way may be appropriate for embedded systems and other systems with resource constraints and no real need for the full keyboard and mouse capabilities.

It is important to remember that the HID driver handles those devices (or actually those interfaces on each device) that claim to comply with the Human Interface Device (HID) specification. However the HID specification doesn't say anything about what the HID driver should do with information received from a HID device, or where the information that is sent to a device comes from, since this is obviously dependent on what the device is supposed to be doing, and what the operating system is. Linux (at the operating system kernel level) supports four interfaces to a HID device - keyboard, mouse, joystick and a generic interface, known as the event interface. These are implemented by the Input device level.

HID Mouse Configuration

In the kernel configuration stage, you need to turn on USB Human Interface Device (HID) support in the USB support and Mouse Support in the Input core support. You don't need to worry about the screen resolution entries for a normal mouse - these are for mouse-like devices such as a graphics tablet. Do not turn on USB HIDBP Mouse support. Perform the normal kernel rebuild and installation steps. If you are installing as modules, you need to load the input.o, hid.o and mousedev.o modules.

Plug in a USB mouse and check that your mouse has been correctly sensed by the kernel. If you don't have a kernel message, look for the changes to /proc/bus/usb/devices.

Since USB supports multiple identical devices, you can have multiple mice plugged in. You can get each mouse seperately, or you can get them all mixed together. You almost always want the mixed version, and that is what will be used in this example. You need to set up a device node entry for the mixed mice. It is customary to create the entries for this device in the /dev/input/ directory. Use the following commands:

mkdir /dev/input
mknod /dev/input/mice c 13 63

If you cat /dev/input/mice you should see some bizarre looking characters as you move the mouse or click any of the buttons.

If you want to use the mouse under X, you have various options. Which one you select is dependent on what version of XFree86 you are using and whether you are using only USB for your mouse (or mice), or whether you want to use a USB mouse and some other kind of pointer device.

If you want to use the mouse under gpm, run (or kill and restart if it is already running) gpm with the following options. gpm -m /dev/input/mice -t imps2 (as superuser remember). You can make this the default if you edit the initialisation files. These are typically named something like rc.d and are in /etc/rc.d/ on RedHat distributions.

If you have both a USB mouse (or USB mice) and some other kind of pointer device, you may wish to use gpm in repeater mode. If you have a PS/2 mouse on /dev/psaux and a USB mouse (or USB mice) on /dev/input/mice, then the following gpm command would probably be appropriate: gpm -m /dev/input/mice -t imps2 -M -m /dev/psaux -t ps2 -R imps2. Note that this will make the output appear on /dev/gpmdata, which is a FIFO and does not need to be created in advance. You can use this as the mouse "device" to non-X programs, and both mice will work together.

Keyboard Configuration

You may not need any operating system support at all to use a USB keyboard if you have a PC architecture. There are several BIOS available where the BIOS can provide USB support from a keyboard plugged into the root hub on the motherboard. This may or may not work through other hubs and does not normally work with add-in boards, so you might want to add in support anyway. You definately want to add keyboard support if you add any operating system support, as the Linux USB support will disable the BIOS support. You also need to use Linux USB keyboard support if you want to use any of the "multimedia" types keys that are provided with some USB keybords.

In the kernel configuration stage, you need to turn on USB Human Interface Device (HID) support in USB support and Keyboard support in Input core support. Do not turn on USB HIDBP Keyboard support. Perform the normal kernel rebuild and installation steps. If you are installing as modules, you need to load the hid.o, input.o and keybdev.o modules.

Check the kernel logs to ensure that your keyboard is being correctly sensed by the kernel.

At this point, you should be able to use your USB keyboard as a normal keyboard. Be aware that LILO is not USB aware, and that unless your BIOS supports a USB keyboard, you may not be able to select a non-default boot image using the USB keyboard. I have personally used only a USB keyboard (and USB mouse) and have experienced no problems.

USB Joystick and Gamepad support

In the kernel configuration stage, you need to turn on USB Human Interface Device (HID) support in USB support and Joystick support in Input core support. Perform the normal kernel rebuild and installation steps. If you are installing as modules, you need to load the hid.o, input.o and joydev.o modules.

You need to set up a device node entry for the joystick. It is customary to create the entries for USB device in the /dev/input/ directory. You can use the following commands to create four device nodes, although there is no reason why you can not use more:

mknod /dev/input/js0 c 13 0
mknod /dev/input/js1 c 13 1
mknod /dev/input/js2 c 13 2
mknod /dev/input/js3 c 13 3

If you plug in a gamepad or joystick and cat /dev/input/js0 you should see some bizarre looking characters as you move the stick or click any of the buttons.

You should now be able to use the USB joystick or gamepad with any of the normal games or other joystick compatible applications.