Enabling XO features on other distributions

It is fairly straightforward to get Linux distributions to boot and run on the XO, since it is a "just" an X86 computer. The XO has several unique features that require additional steps to enable.

This work is present in the Fedora adaptation that is the normal operating system for OLPC OS images (presumably the changes are either in olpc-specific packages or modifications to Fedora packages, see a recent build log). This page documents the changes that other Linux distributions require.

Input controls

Controlling the backlight

The XO display has two controls

1. The backlight brightness (range 0-15)

control or read the brightness through the sysfs file (as of 2.6.25) /sys/class/backlight/dcon-bl/brightness

2. Display mode (high-res vs simulated RGB)

Control or read the mode through the sysfs file (as of 2.6.25) /sys/devices/platform/dcon/output

The high-res mode is 1200x900, the blurred mode is ~800x600.

A 'normal' display has three color pixels for each display pixel, the XO display has one color for each display pixel, and the color is always on when the backlight is on, so to display a color display (or even a white point). this means that if the mode is not in simulated RGB mode and the backlight is on the display will look very strange as different pixels will have different colors.

the standard software for the XO switches to high-res mode when the backlight turns off completely, and simulated RGB mode when the backlight is on.

• See http://dev.laptop.org/~pgf/brightness.sh.txt for an example script to control the brightness and switch the mode appropriatly.

Gamepad keys

You can see what the kernel receives with "showkey --scancodes", see what it translates them to with "showkey", and see what X thinks about it with "xev".

On a traditional PC keyboard, the keypad area to the right contains duplicate arrow, pgup/down and home/end keys that are operational when numlock is not in effect. The gamepad produces the same keycodes that those keypad keys do, thus the dpad produces keypad up/down/left/right, and the circle/cross/square/check keys produce the traditional keypad page up/down and home/end.

To act on the keys, you could run a very simple daemon that eavesdrops on an /dev/input/eventNN node in order to support XO's multi-media keyboard keys. if there's not already a packaged way of doing it.

Scan codes

See Ec specification#KeyCodes for Buttons for the direction pad, gamepad, and screen rotate keys around the XO-1 display.

Some other keys on the keyboard:

key	press	release
Search key (to Journal), 2nd key from the left on the top row of keys	press e0 79	release e0 f9
2nd key from the right on the top row of keys	press e0 6e	release e0 ee
frame (right key on top row)	press e0 5d	release e0 dd
x/ (below keyboard)	press 73	release f3
left hand	press e0 5b	release e0 db
right hand	press e0 5c	release e0 dc
right alt	press e0 38	release e0 b8
view source key	(fn + space) 59 (fn key) followed by e0 56	release is e0 d6 (the d9 release of the fn key may come before or after the release of the view source key)

See https://bugzilla.redhat.com/show_bug.cgi?id=468744 for a possible keymap to use

Predefined function key actions

The XO keyboard's function keys have pre-defined meanings printed on them, e.g. F11 is volume down.

The Sugar code that implements some of these meanings is view/keyhandler.py, see source in git.

xbindkeys

A distro could use xbindkeys to bind the special XO keys. In .xbindkeysrc, you would add an entry for the screen rotate keys that invokes /usr/bin/rotate_screen.py.

Stylus pad

The extended stylus pad either side of the track pad. Note this feature may be removed from future hardware.

Lid sensors

These need to trigger screen off or enter e-book mode.

Suspend/resume

Should work if you use the official OLPC kernel and install the OHM packages.

EC interface

The embedded controller can provide battery info and charge status. This may show up under the power interfaces, may not have stable API.

Mesh mode

XO uses special firmware to implement a early draft of 802.11s mesh networking (??)

See also

Distro version migration nastiness records some of the changes to Fedora packages that the OLPC OS images require.