Xorg framebuffer and brightness of screen

Riza Dindir riza.dindir at gmail.com
Fri Nov 12 05:36:19 UTC 2021

Hello Ken.

On Fri, Nov 12, 2021 at 12:56 AM Ken Moffat <zarniwhoop at ntlworld.com> wrote:
> On Thu, Nov 11, 2021 at 10:16:18AM +0300, Riza Dindir wrote:
> > Hello Ken
> >
> > I am using gop, and a framebuffer. When i try to use the xrandr, it says
> > "gamma is set to 0", or "failed to get size of gamma for output default".
> >
> > I can set the gamma uaing xgamma and in the xorg.conf file.
> >
> > Riza
> >
> No idea what gop is - google suggests it's the american republican
> party ;-)

:D That is the graphics output protocol.

My radeon device is not recognized by the kernel (netbsd) and I am
using a framebuffer.

> Did you search for that "failed to get" message ?  Google gives me a lot of
> different matches, some for failing to correctly add a new mode,
> others for running with nvidia drivers or in virtualbox, or with out
> of date manufacturer's video driver.
> https://askubuntu.com/questions/441040/failed-to-get-size-of-gamma-for-output-default-when-trying-to-add-new-screen-res
> For an ubuntu-based kernel with at-the-time recent intel graphics
> hardware, adding a boot arg to enable alpha-quality intel support.
> https://itectec.com/ubuntu/ubuntu-xrandr-failed-to-get-size-of-gamma-for-output-default-for-mdp-type-connection/
> In short, finding the answer really does seem to depend on what
> hardware and distro are in use.  I'm assuming you're using some sort
> of linux.

What I am trying to do is reduce the brightness of the LCD on my
laptop. Since I am using a framebuffer, I thought that I could do that
with the gamma values. But xrandr fails with  a message relating to
the gamma values being 0 or not set.

> ĸen
> --
> Vetinari smiled. "Can you keep a secret, Mister Lipwig?"
> "Oh, yes, sir. I've kept lots."
> "Capital. And the point is, so can I. You do not need to know.”


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