螢幕亮度快速鍵

1. MSI PS 42 鍵盨 Fn+Up 增加亮度，Fn+Down 降低亮度，Fn+Up 不但無法工作，而且 Fn+Down 一按就降低亮度到全黑，即使再按 Fn+Up 也無法叫醒。查看 /var/log/messages Fn+Up (e078), Fn+Down (e077) keycodes 沒有對應。

   [root@dywmsi ~]# tail -4 /var/log/messages
   Jun 13 06:42:26 dywmsi kernel: atkbd serio0: Unknown key released (translated set 2, code 0xf7 on isa0060/serio0).
   Jun 13 06:42:26 dywmsi kernel: atkbd serio0: Use 'setkeycodes e077 <keycode>' to make it known.
   Jun 13 06:42:27 dywmsi kernel: atkbd serio0: Unknown key released (translated set 2, code 0xf8 on isa0060/serio0).
   Jun 13 06:42:27 dywmsi kernel: atkbd serio0: Use 'setkeycodes e078 <keycode>' to make it known.
   

2. xmodmap 查詢有關 brightness 的 keycodes。

   [root@dywmsi ~]# xmodmap -pke | grep -i bright
   keycode 232 = XF86MonBrightnessDown NoSymbol XF86MonBrightnessDown
   keycode 233 = XF86MonBrightnessUp NoSymbol XF86MonBrightnessUp
   keycode 237 = XF86KbdBrightnessDown NoSymbol XF86KbdBrightnessDown
   keycode 238 = XF86KbdBrightnessUp NoSymbol XF86KbdBrightnessUp
   

3. 設定 Fn+Up (e078) 的 keycode 233， Fn+Down (e077) keycode 232。

   [root@dywmsi ~]# setkeycodes e078 233
   [root@dywmsi ~]# setkeycodes e077 232
   

4. 將 Fn+Up 及 Fn+Down 寫入開機執行腳本 rc.local，雖然測試結果還是無效，但不會再產生錯誤訊息。

   [root@dywmsi ~]# vim /etc/rc.d/rc.local 
   [root@dywmsi ~]# tail -2 /etc/rc.d/rc.local 
   setkeycodes e078 233
   setkeycodes e077 232
   

5. 由於 Xorg 使用的 Driver 是 modesetting，不是 Intel，調整亮度的 xbacklight 無法使用。要使用 xrandr 調整亮度，其參數必須隨亮度大小改變，無法固定。因此，自行撰寫腳本 xbacklight.sh 放在 /usr/bin，以目前亮度固定增減比率做調整：

   [root@dywmsi ~]# cat /usr/bin/xbacklight.sh 
   #!/bin/bash
   max=$(cat /sys/class/backlight/intel_backlight/max_brightness)
   actual=$(cat /sys/class/backlight/intel_backlight/actual_brightness)
   [[ $1 =~ inc ]] && brightness=$((actual*2)) 
   [[ $1 =~ dec ]] && brightness=$((actual/2))
   [[ $brightness -gt $max ]] && brightness=$max
   [[ $brightness -le 0 ]] && brightness=1
   sudo sh -c "echo $brightness > /sys/class/backlight/intel_backlight/brightness"
   

6. 圖形界面自訂 Fn+Up 及 Fn+Down 快速鍵，執行 xbacklight.sh。

   System -> Preference -> Keyboard Shortcuts
   Add
   Custom Shortcuts
   BrightnessUp XF86KbdBrightnessUp NoSymbol XF86KbdBrightnessUp
   BrightnessDown XF86KbdBrightnessDown NoSymbol XF86KbdBrightnessDown
   

7. BrightnessUp 及 BrightnessDown 的執行命令分別為：

   BrightnessUp:  /usr/bin/xbacklight.sh inc
   BrightnessDown:  /usr/bin/xbacklight.sh dec