Problem binding a shortcut to a function / multimedia key

Question

I want to connect a batch script to a shortcut. When I bind it under System Settings > Keyboard > Shortcuts it works with every key, except my brightness keys from my external Apple keyboard.

The brightness keys are recognized in showkey with the keycode 224 and 225.

xev output:

FocusOut event, serial 41, synthetic NO, window 0x4000001,
mode NotifyGrab, detail NotifyAncestor

FocusIn event, serial 41, synthetic NO, window 0x4000001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 41, synthetic NO, window 0x0,
    keys:  0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0 

Any suggestions what I can do?

Answer 1

Solution using udev

Since HAL is deprecated and udev is now used, this approach is preferred over my other answer (although I think that the solution using HAL is simpler).

However for many function keys you can simply use System Settings > Keyboard > Shortcuts to bind a script, try this first! It saves you a lot of trouble. For for instance the brightness keys this doesn't work (I don't have a clue why not), so if you want to know how to change the behavior of for example the brightness keys, read on.

NOTE: If you are running a Samsung notebook you can fix all (depending on model) function keys by installing the samsung-tools package from http://www.voria.org/forum/

This howto assumes you know how to use a terminal, and uses the vim editor. If you don't know vim please replace it in the commands by either gedit or nano.

---

Determining your keyboard

/lib/udev/findkeyboards

should print the keyboards that are connected to the computer, in my case

USB keyboard: input/event9
USB keyboard: input/event7
AT keyboard: input/event4

Now there are two options:

• USB keyboards:
  If you want to remap your USB keyboard, inspect them by running

  udevadm info --export-db | awk '/event9/' RS="" | grep -P 'ID_(VENDOR|MODEL)(?!_ENC)'
  

  where you have to replace the 9 in the awk statement by the correct number. The output should be similar to

  E: ID_MODEL=USB_Receiver
  E: ID_MODEL_ID=c52b
  E: ID_VENDOR=Logitech
  E: ID_VENDOR_ID=046d
  

  which correctly indicates that my keyboard is handled via my Logitech USB Receiver (input/event7 turned out to be my Logitech G9 mouse which has some programmable buttons).

• Laptop Keyboard :
  If you want to remap your laptop keyboard, you should remember the number for the AT keyboard which is 4 in my case. Also get the dmi information for your laptop:

  cat /sys/class/dmi/id/sys_vendor
  

  which is in my case

  SAMSUNG ELECTRONICS CO., LTD.
  

  and

  cat /sys/class/dmi/id/product_name
  

  which is in my case

  305U1A
  

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Determine your current mapping of your function keys

Now we can determine our current keymapping by listening to the keyboard (insert correct number)

sudo /lib/udev/keymap -i input/event4

you can exit this command by using Esc on the keyboard, or Ctrl+c on another keyboard.

If your screen starts scrolling down very hard, press Esc and Ctrl+c a few times and try again with

sudo /lib/udev/keymap -i input/event4 2> /dev/null

or, if you still have the scrolling issue

sudo /lib/udev/keymap -i input/event4 > ~/keymap.log

In the last case you will still have the scrolling but if you press the functions keys they should go into ~/keymap.log where you can read them later.

Now we can check the current mapping of your Function keys by pressing them, which should give you a list like (this is my Fn+F1 through Fn+F12):

scan code: 0xCE   key code: kpplusminus
scan code: 0x89   key code: brightnessdown
scan code: 0x88   key code: brightnessup
scan code: 0x82   key code: switchvideomode
scan code: 0xF9   key code: f23
scan code: 0xA0   key code: mute
scan code: 0xAE   key code: volumedown
scan code: 0xB0   key code: volumeup
scan code: 0x43   key code: f9
scan code: 0x44   key code: f10
scan code: 0xB3   key code: prog3
scan code: 0x86   key code: wlan

Now write down the scan codes for which you want the behavior to change.

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Changing the key codes for the scan codes

If you see the key code clearly doesn't cover what you expect the key to do you can have a look in /usr/include/linux/input.h under Keys and buttons to see if there is a key code that better matches what you actually want to happen. The key codes there are in the format KEY_KEYCODE and you have have to write down the part after KEY_ in lowercase. Sometimes changing this is enough to solve the problem.

The brightness keys however often have the right keycode associated with them, and this is what doesn't allow them to be remapped. So we need to change them to other keycodes. We will use prog1 and prog2 for this example because these aren't in use on my computer, however you can also use f13 through f24, or f20 through f24 if you have an Apple keyboard which has F1 through F19 keys.

1. Create a custom keymap:
   Create a keymap file in the directory /lib/udev/keymaps with a suitable name, have a look at the output of ls /lib/udev/keymaps to see for suitable names. I am going with custom-brightness for the purpose of this question.

   sudo vim /lib/udev/keymaps/custom-brightness
   

   and enter the scan codes of the keys you want to change followed by the scancodes you want them to have. My custom-brightness looks like this:

   # /lib/udev/keymaps/custom-brightness
   
   0x89 prog1
   0x88 prog2
   

2. Create a custom key release file. Only if you are changin your laptop keyboard:
   Sometimes the key release event is not properly send, causing the computer to hang. To avoid this we will also write a custom key release file

   sudo vim /lib/udev/keymaps/force-release/custom-brightness
   

   this file should contain the same scan codes, mine looks like

   # /lib/udev/keymaps/force-release/custom-brightness
   
   0x89
   0x88
   

---

Make sure that the new mappings are loaded in the rules files
Now we need to make sure that your mappings are loaded. We can do this by editing /lib/udev/rules.d/95-keymap.rules, so it is smart to make a backup

Again we have two options:

• USB keyboards:
  Since you have a USB keyboard you should add your entry under LABEL="keyboard_usbcheck" and it should be past the other entries of your keyboard manufacturer. This is because my keyboard with

  E: ID_MODEL=USB_Receiver
  E: ID_MODEL_ID=c52b
  E: ID_VENDOR=Logitech
  E: ID_VENDOR_ID=046d
  

  is already matched by one of the rules, and otherwise it gets overwritten.
  Add the following rule, where you should change the ID_VENDOR_ID and ID_MODEL_ID and the name of your keymap appropiately

  ENV{ID_VENDOR_ID}=="046d", ENV{ID_MODEL_ID}=="c52b", RUN+="keymap $name custom-brightness"
  

• Laptop keyboard:
  If /lib/udev/findkeyboards reported your laptop keyboard as AT keyboard your rule should go under LABEL="keyboard_vendorcheck", otherwise put it under LABEL="keyboard_modulecheck". Again put it under the other entries for your laptop manufactorer. Add the following rule (SAMSUNG ELECTRONICS CO., LTD. is bit long so I used a wildcard`)

  ENV{DMI_VENDOR}=="SAMSUNG*", ATTR{[dmi/id]product_name}=="305U1A", RUN+="keymap $name custom_brightness"
  

  Now also add a rule to /lib/udev/rules.d/95-keyboard-force-release.rules after backing it up

  sudo cp /lib/udev/rules.d/95-keyboard-force-release.rules /lib/udev/rules.d/95-keyboard-force-release.rules.bak
  sudo vim /lib/udev/rules.d/95-keyboard-force-release.rules
  

  Again under the other entries of your manufacturer add

  ENV{DMI_VENDOR}=="SAMSUNG*", ATTR{[dmi/id]product_name}=="305U1A", RUN+="keyboard-force-release.sh $devpath custom_test"
  

---

Make sure udev loads the new rules
To load the new rules run

sudo adevadm trigger

NOTE: udevadm control --reload-rules (still in instructions on many websites) does not work.

Now check if the rules were applied successfully by

sudo /lib/udev/keymap -i input/event4

which should now report for the brightness keys

scan code: 0x89   key code: prog1
scan code: 0x88   key code: prog2

---

Remap the keys in System Settings
If the last step reported the correct key codes, either the keys start automatically working (in case they first had the wrong key codes).

For the brightness you still have to bind the keys to a scrip which is now possible using System Settings > Keyboard > Shortcuts.

Enjoy

---

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Notes:

• If your keys had the wrong key code and were fixed by this approach, please follow the instructions in /usr/share/doc/udev/README.keymap.txt.gz (you can open this without extracting using zless) and send your results the email adres mentioned there, then the changes can be included in the next release. Many users will benefit!

• Many thanks to this helpful post by Vaidas Jablonskis.

Answer 2

Solution using halevt

According to the man pages halevt is a generic handler for HAL events. It is deprecated and replaced by udev, but since I don't know enough about udev I will give a halevt solution.

EDIT: after some serious sweat, I managed to do this in udev. See my other answer.

I will use vim to edit files, but if you don't know vim you can replace it by nano or gedit.

Installing halevt

sudo apt-get update && sudo apt-get install halevt

Determining which events you want to bind to a script
Stop the halevt daemon which is already running:

sudo /etc/init.d/halevt stop

Now see if halevt can recognize the events of the keys you want to use, start the listener:

sudo -u halevt halevt -fig:plugdev

Now press the function key on your keyboard you want to bind the script to. I know that the OP wants to get his brightness keys working, so let's go with that. The output for the brightness keys should look something like this:

Condition: /org/freedesktop/Hal/devices/platform_i8042_i8042_KBD_port_logicaldev_input,ButtonPressed (brightness-down)
Condition: /org/freedesktop/Hal/devices/platform_i8042_i8042_KBD_port_logicaldev_input,ButtonPressed (brightness-up)

You can see that the brightness-down and brightness-up events are transmitted.

Bind the event to a script
Now edit the file /etc/halevt/halevt.xml:

sudo vim /etc/halevt/halevt.xml

and add the following lines ( I did it at the bottom, just before </halevt:Configuration>):

<halevt:Device match="hal.info.category = input">

    <halevt:Condition name="ButtonPressed" value="brightness-up" exec="sudo /home/user/brightness-script.sh up"/>

    <halevt:Condition name="ButtonPressed" value="brightness-down" exec="sudo /home/user/brightness-script.sh down"/>

</halevt:Device>

where of course you should change value to the event that you got from the listener, and exec by the command you want to execute.

Give the halevt user permission to do the command or script
Since the halevt daemon is run as the halevt user you have to give it permission to do what you specified in exec.

Run (remember to replace vim by your editor of choice)

sudo EDITOR=vim visudo

and add the following lines at the bottom

halevt ALL=(root) NOPASSWD: /home/user/brightness-script.sh 

and save and quit.

Make sure your script is executable

sudo chmod +x /home/user/brightness-script.sh

Start the halevt daemon again

sudo /etc/init.d/halevt start

And it should be working!