How to set brightness and color temperature in iMac late 2009 after setting nomodeset? | pressku.com

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I americium moving Kubuntu 22.04 connected an iMac precocious 2009 27 inch. It is besides known arsenic iMac 11,1.

This machine has AMD ATI Mobility Radeon HD 4850 graphics, and it only shows a achromatic surface beyond grub unless nan nomodeset action is set.

Now, location is nary measurement to alteration brightness aliases colour temperature.

The xrandr output is

xrandr: Failed to get size of gamma for output default Screen 0: minimum 2560 x 1440, existent 2560 x 1440, maximum 2560 x 1440 default connected superior 2560x1440+0+0 0mm x 0mm 2560x1440 93.00*

xrandr cannot alteration surface opposition because it cannot group gamma size. As a result, devices for illustration redshift (or KDE Night Color) do not work.

The output of ls /sys/class/backlight/ is blank. I tried mounting acpi_backlight=vendor and acpi_backlight=native successful /etc/default/grub, but it does nothing.

Here is nan output of sudo lshw -c video

*-display UNCLAIMED description: VGA compatible controller product: RV770/M98L [Mobility Radeon HD 4850] vendor: Advanced Micro Devices, Inc. [AMD/ATI] beingness id: 0 autobus info: pci@0000:01:00.0 version: 00 width: 64 bits clock: 33MHz capabilities: p.m. pciexpress msi vga_controller bus_master cap_list configuration: latency=0 resources: memory:c0000000-cfffffff memory:d0620000-d062ffff ioport:2000(size=256) memory:d0600000-d061ffff *-graphics product: EFI VGA beingness id: 1 logical name: /dev/fb0 capabilities: fb configuration: depth=32 resolution=2560,1440

How to group brightness and colour temperature? Even if xrandr does not work, location is immoderate package that is showing nan colors successful screen. Is location immoderate measurement to alteration its opposition aliases colour temperature?

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