The colours on my monitor are washed out, from being too bright.

Previously, I was running nvidia proprietary drivers, and I could adjust that with the xgamma tool.

After switching to Nouveau, I can no longer control the gamma with xgamma:

$ xgamma -gamma 0.8
-> Red 1.000, Green 1.000, Blue 1.000
<- Red 1.000, Green 1.000, Blue 1.000

The kernel reports this about nouveau on boot:

$ journalctl -b | grep nouveau
kernel: nouveau 0000:01:00.0: vgaarb: deactivate vga console
kernel: nouveau 0000:01:00.0: NVIDIA GA104 (b74000a1)
kernel: nouveau 0000:01:00.0: bios: version 94.04.25.40.f1
kernel: nouveau 0000:01:00.0: fb: 8192 MiB GDDR6
kernel: nouveau 0000:01:00.0: DRM: VRAM: 8192 MiB
kernel: nouveau 0000:01:00.0: DRM: GART: 536870912 MiB
kernel: nouveau 0000:01:00.0: DRM: BIT table 'A' not found
kernel: nouveau 0000:01:00.0: DRM: BIT table 'L' not found
kernel: nouveau 0000:01:00.0: DRM: TMDS table version 2.0
kernel: nouveau 0000:01:00.0: DRM: DCB version 4.1
kernel: nouveau 0000:01:00.0: DRM: DCB outp 00: 04800f86 04600020
kernel: nouveau 0000:01:00.0: DRM: DCB outp 01: 04000f82 00020020
kernel: nouveau 0000:01:00.0: DRM: DCB outp 02: 04011f72 00020010
kernel: nouveau 0000:01:00.0: DRM: DCB outp 04: 02822f66 04600020
kernel: nouveau 0000:01:00.0: DRM: DCB outp 05: 02022f62 00020020
kernel: nouveau 0000:01:00.0: DRM: DCB outp 07: 02033f52 00020010
kernel: nouveau 0000:01:00.0: DRM: DCB outp 08: 01844f36 04600010
kernel: nouveau 0000:01:00.0: DRM: DCB outp 09: 01044f32 00020010
kernel: nouveau 0000:01:00.0: DRM: DCB conn 00: 02000046
kernel: nouveau 0000:01:00.0: DRM: DCB conn 01: 01000161
kernel: nouveau 0000:01:00.0: DRM: DCB conn 02: 00020246
kernel: nouveau 0000:01:00.0: DRM: DCB conn 03: 00010361
kernel: nouveau 0000:01:00.0: DRM: DCB conn 04: 00001446
kernel: nouveau 0000:01:00.0: DRM: MM: using COPY for buffer copies
kernel: nouveau 0000:01:00.0: DRM: allocated 1920x1200 fb: 0x200000, bo 00000000693bc1c2
kernel: fbcon: nouveaudrmfb (fb0) is primary device
kernel: nouveau 0000:01:00.0: [drm] fb0: nouveaudrmfb frame buffer device
kernel: [drm] Initialized nouveau 1.3.1 20120801 for 0000:01:00.0 on minor 0
gnome-shell[1141]: Added device '/dev/dri/card0' (nouveau) using non-atomic mode setting.

GPU: Nvidia RTX 3070

kernel: 5.18.1

OS: Ubuntu 22.04

libdrm-nouveau2: 2.4.110-1ubuntu1

UPDATE

I pulled out the RTX3070, and now use Alderlake Integrated graphics, which has the same issue:

$ lshw -c video
WARNING: you should run this program as super-user. *-display description: VGA compatible controller product: AlderLake-S GT1 vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 logical name: /dev/fb0 version: 0c width: 64 bits clock: 33MHz capabilities: vga_controller bus_master cap_list rom fb configuration: depth=32 driver=i915 latency=0 resolution=1920,1200 resources: iomemory:600-5ff iomemory:400-3ff irq:145 memory:6002000000-6002ffffff memory:4000000000-400fffffff ioport:6000(size=64) memory:c0000-dffff memory:4010000000-4016ffffff memory:4020000000-40ffffffff
WARNING: output may be incomplete or inaccurate, you should run this program as super-user.
$ xgamma -gamma 0.6
-> Red 1.000, Green 1.000, Blue 1.000
<- Red 1.000, Green 1.000, Blue 1.000

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