前情提要：我的笔记本，东芝SatelliteL600-22B，生产日期2010年。
自从装了Ubuntu14.04，小生就经常处于被亮瞎的状态，因为亮度调节是失效的，默认应该是开了最高亮度。
Ubuntu的linux一直是业内驱动比较全的系统，一般的硬件都不需要特别的驱动，更不用说我的显卡还是A卡了，查了一下资料，找到了许多方法，一一试了一遍，可是还是没有任何改观。无奈为了保证开机不被亮瞎，小生机智地换成了黑色调的壁纸，然而，用gedit等写报告的时候，纯白的背景，你懂的。。。
求助度娘无效，最后还是找了维基，如下
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There are many ways to control brightness. According to this discussion[1] and this wiki page [2], the control method could be divided into these categories:
brightness is controlled by vendor specified hotkey. And there is no interface for OS to adjust brightness.
brightness is controlled by OS:
brightness could be controlled by ACPI
brightness could be controlled by graphic driver.
All methods expose themselves to the user by /sys/class/brightness. And xrandr/xbacklight could use this folder and choose one method to control brightness. But it is still not very clear which one xbacklight prefers by default. See FS#27677 for xbacklight, if you get "No outputs have backlight property." There is a temporary fix if xrandr/xbacklight does not choose the right directory in /sys/class/brightness: You can specify the one you want in xorg.conf by setting the "Backlight" option of the Device section to the name of that directory
brightness is controlled by HW register throught setpci
ACPIIt is often possible to adjust the backlight by ACPI. This controls the actual LEDs or cathodes of the screen. When this ACPI option is available, the illumination is controllable using a GUI slider in the Display/Screen system settings or by simple commands on the CLI.
Different cards might manage this differently. Check /sys/class/backlight to find out:
# ls /sys/class/backlight/intel_backlight
So this particular backlight is managed by an Intel card. It is called acpi_video0 on an ATI card. In the following example, acpi_video0 is used.
The directory contains the following files and folders:
actual_brightness brightness max_brightness subsystem/ uevent
bl_power device/ power/ type
The maximum brightness (often 15) can be found by running cat:
# cat /sys/class/backlight/acpi_video0/max_brightness
15
Brightness can then be set (as root) with echo. Obviously you cannot go any higher than your screen's maximum brightness. The values for maximum brightness and brightness in general vary wildly among cards.
# echo 5 > /sys/class/backlight/acpi_video0/brightness
Sometimes ACPI does not work well due to different motherboard implementations and ACPI quirks. This include some models with dual graphics (e.g. Nvidia-optimus/Radeon with intel (i915)) and some examples with this problem in notebooks such as Dell Studio, Dell XPS 14/15/17 and some Lenovo series, Kamal Mostafa kernel developer make patches for solved this issue included after 3.1 kernel version. You can try adding the following kernel parameters in your bootloader(grub, syslinux...) to adjust ACPI model:
acpi_osi=Linux acpi_backlight=vendor
or
acpi_osi=Linux acpi_backlight=legacy
acpi_backlight=vendor will prefer vendor specific driver (e.g. thinkpad_acpi, sony_acpi, etc.) instead of the ACPI video.ko driver.
```
大概就是说问题就在
acpi_backlight= 后面默认的时系统的硬盘，而调节亮度的大概是在Bios上
所以只要sudo gedit /etc/default/grub,
把GRUB_CMDLINE_LINUX="“改为GRUB_CMDLINE_LINUX="acpi_osi=Linux acpi_backlight=vendor"
保存后sudo update-grub && sudo reboot即可。
