The factory image adds a kernel boot parameter for the backlight, which is added by the workaround-native-backlight-trusty package. It adds the video.use_native_backlight=1 parameter.
Thanks for the update. I've added that kernel parameter to try and I can't see any difference. I guess I'll need to go back to the factory image to compare.
I'm happy to admit I've got it wrong. I went back to factory and I found the steps to be pretty much the same.
Both Dell OEM Ubuntu 14.04 and Ubuntu stock 15.04 are both using video.use_native_backlight=1. The brightness steps are slightly different. For example in 15.04 the brightness steps 0, 46, 92, 138 ... whereas in Dell 14.04 I think I observed 0, 45, 90, 135... Something like that. But the ultimate minimum and maximum values are 0-937 and the steps appear to be numerically linear.
The only difference I can really observe is that the 14.04 at zero doesn't completely go off at zero; it leaves a negligible brightness that is actually pretty workable in a dark room, whereas 15.04 at zero is completely off and the first step up from zero is brighter than the 14.04 is at zero (still pretty dim then).
What would be the cause of this? I don't know. They both seem to have the same drivers listed by lshw and modinfo, and they both feature the same /sys/class/backlight/intel_backlight 'files'. Perhaps somewhere in the kernel the interpretation of the firmware values has been adjusted slightly?
Why am I going into so much detail? Only because I've let myself become too obsessed about a non-problem and want anyone else so inclined to avoid wasting their lives like I did. =) (I took video recordings of both to see how the steps compare and I can really see no obvious difference, but I'll save you all the boredom.)
Pros of the Dell 14.04 behaviour: You can get a really dim but visible display which could be useful if you want to preserve battery yet actively waiting for something to happen.
Pros of the stock 15.04 behaviour: You can completely turn off the display if you're having something crunch unattended.
So there, hope that helps anyone with similar doubts to me. I consider this 'not an issue'.
DELL-Jared D
2 Intern
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350 Posts
0
July 13th, 2015 10:00
The factory image adds a kernel boot parameter for the backlight, which is added by the workaround-native-backlight-trusty package. It adds the video.use_native_backlight=1 parameter.
bobmcch
1 Rookie
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32 Posts
0
July 13th, 2015 10:00
Thanks for the update. I've added that kernel parameter to try and I can't see any difference. I guess I'll need to go back to the factory image to compare.
Regards,
Bob
bobmcch
1 Rookie
•
32 Posts
0
July 14th, 2015 14:00
I'm happy to admit I've got it wrong. I went back to factory and I found the steps to be pretty much the same.
Both Dell OEM Ubuntu 14.04 and Ubuntu stock 15.04 are both using video.use_native_backlight=1. The brightness steps are slightly different. For example in 15.04 the brightness steps 0, 46, 92, 138 ... whereas in Dell 14.04 I think I observed 0, 45, 90, 135... Something like that. But the ultimate minimum and maximum values are 0-937 and the steps appear to be numerically linear.
The only difference I can really observe is that the 14.04 at zero doesn't completely go off at zero; it leaves a negligible brightness that is actually pretty workable in a dark room, whereas 15.04 at zero is completely off and the first step up from zero is brighter than the 14.04 is at zero (still pretty dim then).
What would be the cause of this? I don't know. They both seem to have the same drivers listed by lshw and modinfo, and they both feature the same /sys/class/backlight/intel_backlight 'files'. Perhaps somewhere in the kernel the interpretation of the firmware values has been adjusted slightly?
Why am I going into so much detail? Only because I've let myself become too obsessed about a non-problem and want anyone else so inclined to avoid wasting their lives like I did. =) (I took video recordings of both to see how the steps compare and I can really see no obvious difference, but I'll save you all the boredom.)
Pros of the Dell 14.04 behaviour: You can get a really dim but visible display which could be useful if you want to preserve battery yet actively waiting for something to happen.
Pros of the stock 15.04 behaviour: You can completely turn off the display if you're having something crunch unattended.
So there, hope that helps anyone with similar doubts to me. I consider this 'not an issue'.
Regards,
Bob