Screen brightness on an Aspire
Aug 31, 2013 6:07:09 GMT -5
Post by Deleted on Aug 31, 2013 6:07:09 GMT -5
A problem that often arises with recent lap-tops is that it is impossible to control the brightness of the screen. Even under Windows it is sometimes impossible to achieve sufficient dimming, and often under Linux or Unix it is difficult to adjust the brightness at all. Perhaps there is some reason why Taiwanese eyes tolerate glarier screens!
Anyway, in my experience there are all kinds of ways to solve this problem; they vary from one machine to another, and from one operating system to another. So here I will discuss only my experience with the machine I am using at present: an Acer Aspire E1-531.
After installation of OpenBSD, the brightness adjustment keys (Fn-left arrow and Fn-right arrow) have no effect, and the screen, stuck at maximum brightness, is unuseable.
After hunting for quite some time I stumbled upon a hint to the effect that on some machines the screen brightness is controlled by the ACPI system. (Here en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface one may read about all the things such a system might be able to control.)
And after hunting around some more I stumbled upon another hint saying that the ACPI could in fact be disabled, in the following way:
1) When the computer boots up, a prompt is displayed:
boot>
2) Within 5 seconds, type a minus sign followed by the letter c:
-c
3) A new prompt will appear, as follows:
UKC>
4) Type "disable acpi" and hit Enter.
5) Then type "quit" and hit Enter.
6) The system will go ahead and boot normally. Test that the Fn-left arrow and Fn-right arrow combinations now control the brightness. Eureka! Of course all the other ACPI functions will be disabled - I don't know what they consist of, but the only one that I have noticed or missed so far is the Power Off capability. With the ACPI enabled, when I type "halt -p" the operating system halts and the power is turned off. With the ACPI disabled, when I type "halt -p" the operating system halts and the power is NOT turned off. To turn the machine off I have to hold the switch down for five seconds. There may well be a solution, but I have not yet investigated. Can any one tell us how to adjust each of the ACPI functions separately?
7) To make the "disable acpi" permanent it is necessary to code it into the kernel. This may be done as follows:
7a) Make a back-up copy of the kernel: type "cp /bsd /bsd.orig"
7b) Start the config programme thus: "config -e -o bsd.new /bsd" Here "bsd.new" will be the name of the newly configured kernel, and "/bsd" is the current one.
7c) Type the change you want config to make, in this case: "disable acpi"
7d) Type "quit" to save your changes and leave the config programme - sic!
7e) Copy the newly configured kernel to the place where it will be effective: "cp bsd.new /bsd"
8) Now you may type "reboot" to test whether the change has worked.
All this rigmarole really needs to be made automatic does it not!
Anyway, in my experience there are all kinds of ways to solve this problem; they vary from one machine to another, and from one operating system to another. So here I will discuss only my experience with the machine I am using at present: an Acer Aspire E1-531.
After installation of OpenBSD, the brightness adjustment keys (Fn-left arrow and Fn-right arrow) have no effect, and the screen, stuck at maximum brightness, is unuseable.
After hunting for quite some time I stumbled upon a hint to the effect that on some machines the screen brightness is controlled by the ACPI system. (Here en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface one may read about all the things such a system might be able to control.)
And after hunting around some more I stumbled upon another hint saying that the ACPI could in fact be disabled, in the following way:
1) When the computer boots up, a prompt is displayed:
boot>
2) Within 5 seconds, type a minus sign followed by the letter c:
-c
3) A new prompt will appear, as follows:
UKC>
4) Type "disable acpi" and hit Enter.
5) Then type "quit" and hit Enter.
6) The system will go ahead and boot normally. Test that the Fn-left arrow and Fn-right arrow combinations now control the brightness. Eureka! Of course all the other ACPI functions will be disabled - I don't know what they consist of, but the only one that I have noticed or missed so far is the Power Off capability. With the ACPI enabled, when I type "halt -p" the operating system halts and the power is turned off. With the ACPI disabled, when I type "halt -p" the operating system halts and the power is NOT turned off. To turn the machine off I have to hold the switch down for five seconds. There may well be a solution, but I have not yet investigated. Can any one tell us how to adjust each of the ACPI functions separately?
7) To make the "disable acpi" permanent it is necessary to code it into the kernel. This may be done as follows:
7a) Make a back-up copy of the kernel: type "cp /bsd /bsd.orig"
7b) Start the config programme thus: "config -e -o bsd.new /bsd" Here "bsd.new" will be the name of the newly configured kernel, and "/bsd" is the current one.
7c) Type the change you want config to make, in this case: "disable acpi"
7d) Type "quit" to save your changes and leave the config programme - sic!
7e) Copy the newly configured kernel to the place where it will be effective: "cp bsd.new /bsd"
8) Now you may type "reboot" to test whether the change has worked.
All this rigmarole really needs to be made automatic does it not!