问题一: 开机亮度的设置问题，已经解决。
问题二: 在ubuntu下，每次开机的时候，键盘背光灯都亮，需要手工关闭，困惑。Google很久，也没有找到答案。
提示一：
以下英文，没看明白。有明白的请教了。
So, is it possible to have a way to control the keyboard backlight from the command line? That would be great.
When I’m in a bright ambient is sometimes hard to tell whether the keyboard backlit is on or not and I’d really like to use the light sensor to automatically set the desired level in a defined way.
With a sysfs interface to control the backlit, all the problem would be solved.
I tried to see how much power the keyboard backlight requires, this is more or less what I got using powertop [1]:
6.55 W - max brightness
5.75 W - low brighntess
5.25 W - off
As you can see, there’s more than 1 W of difference between off and max brightness, that’s a lot.
/**
What I mean with these numbers is that keeping the backlight on when not required consumes a lot of battery for no reason. This is a problem in bright ambients as you really don’t think about turning the backlight off or you just can’t really see whether is on or off.
smbios-token-ctl is the only solution, but it’s not working perfectly as I can only set the keyboard to its max or turn it off. As shown here above, there’s an important power difference between low and max, so I would like to set the brightness to low sometimes.
***/
提示二：本子是dell xps的，dell on backlit keyboard
输出如下，但是，echo 不起作用。
root@lzd:~# cat /sys/devices/pci0000:00/0000:00:1c.3/0000:09:00.1/leds/mmc0::/brightness
0
root@lzd:~# cat /sys/devices/pci0000:00/0000:00:1c.3/0000:09:00.1/leds/mmc0::/max_brightness
255