我到处寻找这个问题的解决方案，但现在我放弃了，并向各位大师请教。我的问题是，我的联想 Thinkpad X1 Yoga 第一代的屏幕亮度突然开始自动变为非常低的设置。Yoga 有一个英特尔 GPU。我可以使用 Fn+F6 更改亮度，亮度会上升。但仅仅几秒钟后，屏幕又变暗了。此外，如果我使用 Fn+F6 来增加亮度，系统日志中会写入一条错误，内容为：
1 月 5 日 18:16:27 runmil-ubuntugnome gnome-shell[2892]: 目前不支持百分比长度
我安装了亮度控制，但根本不起作用。我还安装了指示器亮度，百分比错误不再显示，但屏幕仍然会自动变暗。以下是日志中的一段代码：
Jan 5 17:58:53 runmil-ubuntugnome pkexec[18418]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 25]
Jan 5 17:59:04 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:04 runmil-ubuntugnome pkexec[18437]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness]
Jan 5 17:59:04 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:04 runmil-ubuntugnome pkexec[18440]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 56]
Jan 5 17:59:04 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:04 runmil-ubuntugnome pkexec[18444]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness]
Jan 5 17:59:05 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:05 runmil-ubuntugnome pkexec[18454]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness]
Jan 5 17:59:05 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:05 runmil-ubuntugnome pkexec[18457]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 112]
Jan 5 17:59:05 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:05 runmil-ubuntugnome pkexec[18461]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness]
Jan 5 17:59:05 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:05 runmil-ubuntugnome pkexec[18467]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness]
Jan 5 17:59:05 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:05 runmil-ubuntugnome pkexec[18470]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 168]
Jan 5 17:59:05 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Jan 5 17:59:05 runmil-ubuntugnome pkexec[18474]: runmil: Executing command [USER=root] [TTY=unknown] [CWD=/home/runmil] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness]
Jan 5 17:59:06 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=121)
Jan 5 17:59:06 runmil-ubuntugnome pkexec[18479]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 34]
Jan 5 17:59:07 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=121)
Jan 5 17:59:07 runmil-ubuntugnome pkexec[18484]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 34]
Jan 5 17:59:37 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=121)
Jan 5 17:59:37 runmil-ubuntugnome pkexec[18505]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 25]
Jan 5 17:59:39 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=121)
Jan 5 17:59:39 runmil-ubuntugnome pkexec[18510]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 25]
Jan 5 17:59:42 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=121)
Jan 5 17:59:42 runmil-ubuntugnome pkexec[18519]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 25]
Jan 5 17:59:42 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=121)
Jan 5 17:59:42 runmil-ubuntugnome pkexec[18524]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 25]
Jan 5 17:59:45 runmil-ubuntugnome pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=121)
Jan 5 17:59:45 runmil-ubuntugnome pkexec[18529]: gdm: Executing command [USER=root] [TTY=unknown] [CWD=/var/lib/gdm3] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 25]
如您所见，gdm 正在运行命令来不时地更改亮度，将其设置为 852 中的 25 或 34。然后我使用 indicator-brightness-adjust --up 进行更新，它首先上升到 56，然后是 112，最后是 168。但仅 1 秒之后，gdm 就会自动将亮度再次更改为 34。
我正在运行完全更新的 Ubuntu 17.10，使用 Gnome 和 Wayland。
我知道我可能安装了某些东西，导致它出现问题，但我找不到是什么原因。它与外接显示器配合使用时没有问题。电池或电源没有差异。我尝试过许多不同的 grub 设置，但都没有奏效。我正在运行 tlp，找不到与此错误有关的任何信息。
我从 10 月份开始运行 Ubuntu 17.10，一直到 12 月中旬都运行良好。我不太清楚具体什么时候，80% 的时间我都连接了外接显示器。
那么，各位大师是否知道如何解决这个问题？