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 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.

HID Mouse Configuration

In the kernel configuration stage, you need to turn on USB Human Interface Device (HID) support and Mouse Support 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.

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.

• You need to edit the XF86Config file (usually /usr/X11R6/lib/X11/XF86Config or /etc/X11/XF86Config).
• If you are using XFree86 version 4.0 or later, add a InputDevice section that looks like the following:

  Section "InputDevice" Identifier "USB Mice" Driver "mouse" Option "Protocol" "IMPS/2" Option "Device" "/dev/input/mice" EndSection

  or, if you want to use a wheel mouse, something like:

  Section "InputDevice" Identifier "USB Mice" Driver "mouse" Option "Protocol" "IMPS/2" Option "Device" "/dev/input/mice" Option "ZAxisMapping" "4 5" Option "Buttons" "5" EndSection

  may be more useful. Consult the XFree86 documentation for a detailed explaination and more examples.
  You also need to add an entry to each applicable ServerLayout Section. These are normally at the end of the configuration file. If you only have a USB mouse (or USB mice), then replace the line with the "CorePointer" entry with the following line:

  InputDevice "USB Mice" "CorePointer"

  If you want to use both a USB mouse (or USB mice) and some other kind of pointer device, then add (do not replace) the following line to the applicable ServerLayout sections:

  InputDevice "USB Mice" "SendCoreEvents"

• If you are using only a USB mouse (or USB mice) with XFree86 3.3, edit the Pointer section so that it looks like the following:

  Section "Pointer" Protocol "IMPS/2" Device "/dev/input/mice" EndSection

• If you are trying to use a USB mouse (or USB mice) in addition to another pointer type device with XFree86 3.3, then you need to use the XInput extensions. Keep the existing Pointer (or modify it as required for the other device if you are doing an initial installation), and add the following entry (anywhere sensible, ideally in the Input devices area):

  Section "Xinput" SubSection "Mouse" DeviceName "USB Mice" Protocol "IMPS/2" Port "/dev/input/mice" AlwaysCore EndSubSection EndSection

• Restart the X server. If you don't have any mouse support at this point, remember that Ctrl-Alt-F1 will get you a virtual terminal that you can use to kill the xserver and start debugging from the error messages.

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 and Keyboard 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 and Joystick 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.

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.