Keyboard mapping, the problem

From: Alain RICHARD (
Date: Thu Dec 28 2000 - 05:07:27 EST


one of the new feature of the new 2.2.18 kernel (at least ppc kernel,
I don't know about the standard kernel) is the new
keyboard mapping.

The idea is that if you set
/proc/sys/dev/mac_hid/keyboard_sends_linux_keycodes to 1, the raw
kaycodes sent by the keyboard are mapped to the "standard" linux
keycodes, i.e. intel PC raw keycodes.

This seams to be a good idea because once this is done, you may use
the standard keyboard mapping tables from the intel linux and don't
have to setup mapping for each plateforms.

The problem is that it is in fact not such a good idea. For example
on the french market here are the description of two mostly
encountered keyboards :

French PC keyboard :

ESC F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12
^2 &/1 /2/~ "/3/# '/4/{ (/5/[ -/6/| /7/` _/8/\ /9/^ /0/@
)//] =/+/} BS
TAB a/A z/Z e/E/ r/R t/T y/Y u/U i/I o/O p/P ^/
$/ CR
CAPS q/Q s/S d/D f/F g/G h/H j/J k/K l/L m/M /% */
SHIFT </> w/W x/X c/C v/V b/B n/N ,/? ;/. :// !/ SHIFT

French Mac Keyboard :

ESC F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12
@/# &/1 /2 "/3 '/4 (/5 /6 /7 !/8 /9 /0 )/
-/_ BS
TAB a/A z/Z e/E r/R t/T y/Y u/U i/I o/O p/P ^/
$/*/ CR
CAPS q/Q s/S d/D f/F g/G h/H j/J k/K l/L m/M /% `/
SHIFT </> w/W x/X c/C v/V b/B n/N ,/? ;/. :// =/+ SHIFT

You may see there are a lot of similarities and differences :

- french keyboards are AZERTY and not QWERTY and both implements the
letters at the same place.

- there is no standard on the french market for the special
characters {} [] _ @ # | ` \ = + ! < > that are very common on a
computer. So PC plateforms implements them very differently than on
the mac plateform, but also than on other plateforms or typewritters.
The problem here is that the french mapping is printed on the
keyboard, so using a french intel linux mapping on a french mac
keyboard is useless (if you type = you get !, and so on).

- on the two plateforms, there are different way of getting the other
characters than lowercase and uppercase. On the PC side, some keys
return a third character by using the ALTGR key (at the right of the
space bar). On the mac side you have to use the OPTION key on either
the left or right of the space bar. This OPTION key is also printed
with as ALT but its function is the same as the ALTGR and not ALT PC

- PC keyboards have several keys without equivalent on the mac side
(WIN keys for example). Mac keyboards also have special keys (for
example the new eject key on recent USB keyboards).

- both plateforms has different ways of mapping special characters.
On the PC side, the ALTGR key is used only on keys with a third
character mapped on it, or with the keypad to generate any ISO-1
code, and there is no special logic on this mapping. On the mac side,
the option key try to have some logic on the mapping and almost all
keys may generate 4 mappings (a, shift a=A, Opt a= (ae), Shift Opt
a= (AE)). In fact on a french mac keyboard, the only key that have
more than 2 characters printed on it is the $/*/ key because of the
recent Euro character addition. Mac users do not need the ALTGR key
99% of the time !

So the new way of mapping mac french keyboard (and probably french
keyboard from the other plateforms but intel) is very bad and
useless. So in all cases, the intel french keyboard mapping is
useless as is on a french mac keyboard and we need to make a special

So the problem is what is the interest if the new mapping ? Why is it
now the new default settings ? In my experience, 80% of the support
problem I have encountered with Linux users on the mac side is with
the setting of a decent keyboard mapping on the console AND on the X

The new raw keycodes mapping is the worst thing we have got for the
linuxppc support; we now have :

- 2 raw keycodes mapping (old ADB one and new keyboard_sends_linux_keycodes)
- 2 logical keycode mapping : one for the console and an other for X.
- at least 4 different X servers to support (XFree 3.3, Xpmac, XFree
4.0, XFree 4.0.[12]). All of theses X server have a different
approach to the mapping problem !
- french logical keyboard mapping are not standard in the
distribution, so the user have to get files elsewhere.

as you may see, this is a lot of different combinations and the user
is very clever when he manage to get its keyboard working !

I think the main problem is that linux do not consider the keyboard
as a real device with a real driver associated with it, so it tries
to implement only one keyboard driver or one keyboard driver per bus
(ADB/USB/PS2), but I think this is not the good solution. For example
there are USB keyboard targetted to the Mac market that have a Mac
mapping printed on it and there are USB keyboards targetted mainly
for the PC market that have a PC mapping printed on it. All are
useable as it under linux intel or linux ppc and this is not the USB
bus that must implies the mapping (this is why I think the remapping
of ADB keycodes to intel linux raw keycodes is not a such good idea).

So we need a clever keyboard abstraction in the linux kernel.

And don't forget that if this problem is not present on the english
market, the rest of the world use diatrical marks or several bytes
per characters (95% of the market ?).

Alain RICHARD <>
Tel : +33 477 79 48 00	 Fax : +33 477 79 48 01
Applications client/serveur, ingnierie rseau et Linux
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