gnome屏幕亮度

Question

当按下亮度键(或在设置中使用滑块)时，Ubuntu的作用就好像它在改变屏幕的亮度，但是亮度不会改变。通过四处打探，我发现我可以用

echo $N > /sys/class/backlight/radeon_bl0/brightness

其中$N为>= 0，$N为<= 255。

• iMac=mc813ll/a
• Ubuntu Release=18.04
• 内核=4.15.0-20-泛型(默认)

相关日志摘录；

> tail -n 2 /var/log/auth.log
May  5 11:44:02 imac pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
May  5 11:44:02 imac pkexec[7310]: $USER: Executing command [USER=root] [TTY=unknown] [CWD=/home/$USER] [COMMAND=/usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 10]

直接试验；

> sudo /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 255
Could not set the value of the backlight: writing '255' to /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0 failed

没有手册页

> man gsd-backlight-helper
No manual entry for gsd-backlight-helper
> man gnome-settings-daemon
No manual entry for gnome-settings-daemon

较长的路径示例；

> echo 20 > /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0/brightness
-bash: echo: write error: Invalid argument

> echo 20 > /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card0/card0-eDP-1/radeon_bl0/brightness

看起来这是src，我如何在内核中告诉GNOME亮度该怎么说呢？

我刚重新启动

/sys/class/backlight/radeon_bl0/brightness

是现在

/sys/class/backlight/radeon_bl1/brightness

或

/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card1/card1-eDP-1/radeon_bl1

所以地点甚至不稳定。

> lspci | grep "VGA compatible controller"
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Whistler [Radeon HD 6730M/6770M/7690M XT]

> sudo dmidecode | grep -A 9 "System Information" | grep "Product Name"
    Product Name: iMac12,2

Answer 1

使用acpi_背光内核参数；

 sudo perl -pi -e 's/(GRUB_CMDLINE_LINUX_DEFAULT="[^"]*)(")/$1 acpi_backlight=vendor$2/g' /etc/default/grub