# Samsung R505 Aura

### LCD Brightness

LCD brightness information can be found in the following files:

/sys/devices/virtual/backlight/acpi_video0/brightness
/sys/devices/virtual/backlight/acpi_video0/actual_brightness
/sys/devices/virtual/backlight/acpi_video0/max_brightness

Since the Fn + Up, Down buttons seem unwilling to work, you can also do the following to adjust the brighness:

    # echo <Number> > /sys/devices/virtual/backlight/acpi_video/brightness

If you have tried this already, you have probably received an error message saying something like "permission denied". Therefore, you first have to change the file owner of /sys/devices/virtual/backlight/acpi_video/brightness to your username. You can do this by

    # sudo chown <usrname> /sys/class/backlight/acpi_video0/brightness

where <usrname> is the name of your user.

#### Making things more convenient: Step 1

The Above command for changing the brightness is not very handy, but this can be fixed with a few shell-scripts designed for this purpose. Consider the following as examples that you may alter to fit your needs.

     [brightnessUp]
     #!bin/bash
     b=`head -1 /sys/class/backlight/acpi_video0/brightness`
     mb=`head -1 /sys/class/backlight/acpi_video0/max_brightness`
     if [ $b -lt $mb ]
     then
         nb=`expr $b + 1`
     else
         nb=`expr $b`
     fi
     echo $nb > /sys/class/backlight/acpi_video0/brightness

     [brightnessDown]
     #!bin/bash
     b=`head -1 /sys/class/backlight/acpi_video0/brightness`
     mb=0
     if [ $b -gt $mb ]
     then
         nb=`expr $b - 1`
     else
         nb=`expr $b`
     fi
     echo $nb > /sys/class/backlight/acpi_video0/brightness

     [brightnessSet]
     #!bin/bash
     mb=`head -1 /sys/class/backlight/acpi_video0/max_brightness`
     if [ $# -ne 1 ]
     then
       echo "Usage: brightnessSet {val}"
     else
         if ([ $1 -le $mb ] && [ $1 -ge 0 ])
         then
             echo $1 > /sys/class/backlight/acpi_video0/brightness
         else
             echo "error: specify brightness in [0-$mb]"
         fi
     fi

     [brightnessGet]
     #!bin/bash
     b=`head -1 /sys/class/backlight/acpi_video0/brightness`
     mb=`head -1 /sys/class/backlight/acpi_video0/max_brightness`
     echo "current screen brightness: $b of $mb"

Using these and defining aliases for these scripts in your .bashrc you can easily control your screen brightness form your terminal.

The Downside of this is obviously that the File /sys/class/backlight/acpi_video0/brightness gets restored (or recreated) on every startup, as it merely represents a register in your graphics device. Therefore, you have to execute the above command for the owner change from "root" to "<usrname>" on every startup. Since this is pretty annoying, there is, of course, a workaround.

#### Making things more convenient: Step 2

To enable you to change the screen brightness without having to manually execute the "sudo chown"-command on every startup, you have to do the following.

First, generate a shell script named "brightnessControl" (or whatever you wish) with the following content:

     [brightnessControl]
     #!/bin/bash
     sudo chown <usrname> /sys/class/backlight/acpi_video0/brightness

Note: You may have to exchange the shebang in the first line with the appropriate one for your shell.

Second, move the shell script into a directory that is within your $PATH variable, e.g.

    # sudo mv brightnessControl /usr/bin/brightnessControl

Now you have to make your script executable by doing

    # sudo chmod 755 /usr/bin/brightnessControl

This would be a nice thing, but sadly, you need root privileges to perform the script you have just written. This is why you have to enable running this script without password. This is done by typing

    # sudo EDITOR=nano visudo

and adding the line

    <usrname> ALL=(ALL) NOPASSWD:/usr/bin/brightnessControl

where <username> again is the name of your user. Be careful - you can mess up quite a lot changing stuff in your sudoers file.

Now you only have to add /usr/bin/brightnessControl to some kind of autostart list of your desktop environment. If you are using LXDE, for example, open the file

    ~/.config/lxsession/LXDE/autostart

(or create it, if it does not exist already) and add the line

    /usr/bin/brightnessControl

Congratulations, you are done! Now you can execute the above scripts at any time. You can define yourself aliases in your .bashrc, or you can just also make them executables via "chmod 755" and move them into one of your $PATH directories, so you can execute them easily.

You can, of course, also define keybindings to execute the commands for you. Depending on whether you made your scripts executable or not the appropriate commands to paste into your keybindings-config-file or gui interface are

    /bin/bash /path/to/your/script (for shell-scripts)
    /path/to/your/executable (for executables)

The appropriate identifiers for the Fn-Up and the Fn-Down keys are "XF86MonBrightnessUp" and "XF86MonBrightnessDown", so you can - if you wish - finally get them to work correctly now.

If you are using LXDE, you can to this by adding the following lines into the <keyboard> section of your ~/.config/openbox/lxde-rc.xml file.

     <!-- Keybindings for screen brightness -->
        <keybind key="XF86MonBrightnessUp">
          <action name="Execute">
            <command>BRIGHTNESS-UP</command>
          </action>
        </keybind>
        <keybind key="XF86MonBrightnessDown">
          <action name="Execute">
            <command>BRIGHTNESS-DOWN</command>
          </action>
        </keybind>

Where "BRIGHTNESS-UP" and "BRIGHTNESS-DOWN" stand for the above mentioned expressions

    /bin/bash /path/to/your/script (for shell-scripts)
    /path/to/your/executable (for executables)

Also, you can simply use the name of your script if you put it into a directory which is contained within your $PATH variable. But remember that these commands are not called within a bash, so you do not have access to your "extended" $PATH variable you might have achieved by changing your .bashrc.

### Audio Volume hotkeys

If you are using LXDE, the following steps will get your Audio Volume hotkeys Fn-Right and Fn-Left as well as Fn-F6 to work.

First, you have to make sure that alsa is configured correctly. You can configure alsa using

    # alsaconfig

Executing

    # alsamixer

you can adjust the volumes to a convenient setting. Then, adding

    @ alsa

to the DAEMONS section of your rc.conf, you can ensure that the values you just specified will be loaded on every startup. Finally, paste the following lines into the <keyboard>-section of your ~/.config/openbox/lxde-rc.xml file.

     <!-- Keybindings for audio volume control -->
        <keybind key="XF86AudioRaiseVolume">
          <action name="Execute">
            <command>amixer -q set PCM 2+ unmute</command>
          </action>
        </keybind>
        <keybind key="XF86AudioLowerVolume">
          <action name="Execute">
            <command>amixer -q set PCM 2- unmute</command>
          </action>
        </keybind><keybind key="XF86AudioMute">
          <action name="Execute">
            <command>amixer -q set Master toggle</command>
          </action>
        </keybind>

Category:

- Samsung