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My Samsung R428 laptop can't adjust the backlight with Ubuntu 12.04. Under Mac OS X 10.8.2, I patched the DSDT file and solved the same problem. I did some search, well, it seems DSDT overriding is no longer suported by Ubuntu. How can I fix this problem?

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A member of the community has described how to do this using grub rather than having to rebuild the kernel with the DSDT override config options enabled, so this may be an easier way to do it, see:

https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1045690

Note that the Ubuntu kernel team disabled the use of DSDT override because it is theoretically possible to damage you machine if it is mis-configured. Also, one can introduce security issues by creating AML that can access memory with kernel privileges. Finally, with a modified DSDT using the DSTD override config option the kernel will be marked as tainted and one will get little or no support from the kernel team with a tainted kernel.

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The ability to load a DSDT in the initramfs was removed in the upstream kernel, not by Ubuntu, and it was not because of security issues ( there are none ), but because the kernel has to start using the DSDT before the initramfs is processed, and it is unsafe to switch after that. –  psusi Dec 4 '12 at 18:56
    
If I recall, we used to include a patch to enable this even after it got dropped upstream and was carried for a few releases but it was dropped because we believed it was unsafe for several reasons. But, it was a while back and I can't recall the exact details now. –  Colin Ian King Dec 4 '12 at 21:02

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