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Thread: HOWTO: Multimedia Keys

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  1. #1
    Join Date
    Nov 2004
    Roma, Italia

    HOWTO: Multimedia Keys

    See also:

    Do you have a keyboard with those neat multimedia buttons, but they don't work with linux? This mini-howto should help you.

    *Quick recipe*
    0. See if your key works with gnome-keybinding-properties, it's under the menu: Desktop/Preferences/Keyboard Shortcuts. If it doesnt' work,

    1. Go to a real console and press your multimedia keys one by one.

    2. Look at the console output to discover which scancodes are generated, you should see something like this:
    atkbd.c: Unknown key pressed (translated set 2, code 0x9e on isa0060/serio0).
    atkbd.c: Use 'setkeycodes e01e <keycode>' to make it known.
    you should find the same information with:
    3. Use setkeycodes to set your keycodes as suggested. (but first use dumpkeys to see which keycodes are free to use).

    4. Put those commands in /etc/init.d/

    5. Open an X terminal:
    xmodmap -pke > xmodmap.conf
    , then edit this file adding the missing keysyms to the right keycodes (use xev to see the keycodes, read the file /usr/lib/X11/XKeysymDB to see which keysyms are available).

    6. From the same terminal:
    sudo cp xmodmap.conf /etc
    cd /etc/X11/gdm/PostLogin
    sudo cp Default.sample Default
    then open the file /etc/X11/gdm/PostLogin/Default with your editor of choice and add this line to it:
    xmodmap /etc/xmodmap.conf
    7. Use gnome keybindings or metacity keybindings to bind actions to your fresh configured keys.

    Woo, that was fast! ;)

    A little background note:
    When you hit a key on your keyboard, the linux kernel generates a raw scancode for it (if it's assigned). Each scancode can be mapped to a keycode.
    This is at _kernel_ level.
    X has a (quasi) total independent way of mapping keys: X reads the kernel keycode table at startup, then map the keycode to its _independent_ keycode table (it's the same as the kernel keycodes but different :)). Then each keycode can be mapped to a keysym, i.e. a string which represent a key or suggest an action.
    Thus to have our keys fully functional, they need a kernel scancode/keycode plus a X keycode/keysym.
    It could seem weird, and it is, but X developers have their reason to keep a separate keyboard mapping from the kernel.
    It's not difficult at all, it's only a quite tedious procedure.

    0.Use gnome-keybinding-properties:
    Try to see if your key works with gnome-keybinding-properties, it's under the menu: Desktop/Preferences/Keyboard Shortcuts.
    If it doesnt' work, or if gnome-keybinding-properties doesn't have a nice default action for your key, you have read the whole howto ;)

    1.Assigning kernel keycodes:
    We are trying to see which keys have already a kernel scancode/keycode and which don't.
    Go to a real console by pressing <ctrl><alt>F1.
    Now if you press your multimedia keys one by one, you should see an output message like this:
    atkbd.c: Unknown key pressed (translated set 2, code 0x9e on isa0060/serio0).
    atkbd.c: Use 'setkeycodes e01e <keycode>' to make it known.
    The same informations can be found typing:
    This is all you need, but before assigning the missing keycode, you need to check which keycodes are available, to avoid conflicts.
    The command returns a list of used scancodes. Just pick the ones without an unassigned keycode (usually from 120 to 255).
    Now you know:
    1.which keys have missing keycodes to map the missing scancode/keycode to make it known
    3.which keycodes are available to use

    So it's time to actually set up these codes, type:
    setkeycodes e01e 120
    where e01e is the scancode suggested in dmesg, and 120 is a free keycode you have to choose.
    Repeat this passage for all your keys which don't generate a scancode/keycode.
    If you want these commands executed at system startup (you want it), add all those setkeycodes statements at the end of the file /etc/init.d/

    Now that you have all your kernel scancodes well generated, move on to:

    2.Assigning X keysyms
    This time you can stay under X ;) X keysyms are a sort of descriptive string like: XF86AudioMedia, XF86WWW etc. but we can't use random names. A list of X keysyms can be found in the file: /usr/lib/X11/XKeysymDB

    Fire up a terminal and type:
    press a multimedia key. If you are lucky it has already a keysym binded to it, so the output of xev for that key will be something like this:
    KeyRelease event, serial 28, synthetic NO, window 0x3200001,
    root 0xb7, subw 0x0, time 137010761, (693,138), root:(705,256),
    state 0x10, keycode 136 (keysym 0x1008ff27, XF86Forward), same_screen YES,
    XLookupString gives 0 bytes:
    The third row is the one of interest: it says that you have a keycode for that key (136) as well as keysym (XF86Forward).
    If you have a keysym then it's all good, you can use that string to represent your key and use gnome keybindings or metacity keybindings to bind the relevant action to it. (See below).
    But probably, you'll find that the key doesn't have any keysym assigned to it, like this:
    KeyRelease event, serial 28, synthetic NO, window 0x3200001,
    root 0xb7, subw 0x0, time 137355697, (401,146), root:(413,264),
    state 0x10, keycode 136 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    In this case you have to assign oyur keysym to the relevant keycode (136) (it doesn't match the kernel keycode for that keys, but it doesn't matter, it's by design).
    This is done with xmodmap.
    First, create a file with your current X keyboard map, in a terminal type:
    xmodmap -pke > xmodmap.conf
    Then you are going to add all the missing keysyms to this file: use xev to see which keycode to use, look in the file /usr/lib/X11/XKeysymDB to find keysym names, open the xmodmap.conf file and fill in the missing keysym using a name which makes sense (i.e. if you have a button with a calculator printed on it, use XF86Calculator as keysym).
    Repeat this passage for all your multimedia keys.
    When finished, you can apply the changes with:
    xmodmap xmodmap.conf
    Now you want to load your new xmodmap.conf when X starts. I've found that the better way is to put the command in the PostLogin script of gdm. (if you use gdm, of course ;))
    sudo cp xmodmap.conf /etc/xmodmap.conf
    cd /etc/X11/gdm/PostLogin
    sudo cp Default.sample Default
    Now open the Default file with your favourite editor and at the end of it add this line:
    xmodmap /etc/xmodmap.conf
    This way you should have all your scancodes/keycodes/keysyms assigned at system and X startup.
    Now you can make something useful with them like:

    3.Using gnome keybindings or metacity to bind commands to keys
    First, try to bind keys with gnome-keybinding-property: it's quicker and it has some nice default action, so launch it from the terminal or from the menu.
    The utility is self-explanatory, but probabily you'll find that some actions don't work (like sleep for example), or they do the wrong thing, or there is no suitable action at all for your key.
    You can address those problems using metacity to bind keys to commands which is a lot more flexible.
    Open a terminal and type:
    or launch it from the menu under Applications/System Tools/Configuration Editor.
    Go under apps/metacity in gconf-editor. You will see 2 rows (among others):
    global_keybindings and keybinding_commands.
    If you click on "global_keybindings", on the right pane you'll find some entry for commands, like:
    run_command_1, run_command_2, etc.
    These have to be filled up with the relevant keysym for your key (like: XF86Play, XF86MyComputer, etc. use xev to see).
    Then you can assign the matching command (or script) on the other row, under "keybinding_commands".
    You have a lot of useful command at your disposal like:
    totem --fullscreen or rhythmbox --next etc.
    Use the command line help of those applications to discover which parameters are available, e.g. totem --help or rhythmbox --help etc.
    For firefox take a look here:

    4.Additional hints
    The actions you want to execute after a key press are limited only by fantasy: bash provides a very powerful scripting language and with hundreds of useful programs out there, there is virtually no limit.
    For example an app you may find useful is xmacro (sudo apt-get install xmacro): it let you play a mouse or a keyboard macro with a command. I've used it to bind my Forward and Back multimedia keys to <Alt>Right and <Alt>Left respectively: this way I can control forward and back in epiphany which doesn't provide a command line option for this task. (it works with every app which takes <Alt>Right and <Alt>Left shortcuts). This is my xmacro script:
    case "$1" in
    sleep .3
    echo -e "KeyStrPress Alt_L \n
            KeyStrPress Right \n
            KeyStrRelease Right \n
            KeyStrRelease Alt_L" | xmacroplay :0 ;;
    sleep .3
    echo -e "KeyStrPress Alt_L \n
            KeyStrPress Left \n
            KeyStrRelease Left \n
            KeyStrRelease Alt_L" | xmacroplay :0  ;;
    exit 0
    Another hint is that if you have a sleep key, and it doesn't work with gnome-keybinding-properties, you can use it at least to shut off your monitor:
    just assign it to the command:
    xset dpms force off
    with metacity.

    If you have a scroll wheel on your keyboard, you can even assign a keybinding to the button under the wheel! Assign it to the "Return" keysym, it will act like a return key.

    That's all!

    p.s.I tried to keep it short but I didn't succeed ;)

    * The Linux keyboard and console HOWTO
    * The Net
    Last edited by piedamaro; December 28th, 2005 at 07:35 PM. Reason: Update


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